Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
Bharat Bhushan r65...@freescale.com writes:
We need to search linux pte to get pte attributes for
setting TLB in KVM.
This patch defines a linux_pte_lookup() function for same.
Signed-off-by: Bharat Bhushan bharat.bhus...@freescale.com
---
arch/powerpc/include/asm/pgtable.h | 35 +++
1 files changed, 35 insertions(+), 0 deletions(-)
diff --git a/arch/powerpc/include/asm/pgtable.h
b/arch/powerpc/include/asm/pgtable.h
index 7d6eacf..fd26c04 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -223,6 +223,41 @@ extern int gup_hugepte(pte_t *ptep, unsigned long sz,
unsigned long addr,
#endif
pte_t *find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea,
unsigned *shift);
+
+static inline pte_t lookup_linux_pte(pgd_t *pgdir, unsigned long hva,
+ unsigned long *pte_sizep)
+{
+ pte_t *ptep;
+ pte_t pte;
+ unsigned long ps = *pte_sizep;
+ unsigned int shift;
+
+ ptep = find_linux_pte_or_hugepte(pgdir, hva, shift);
+ if (!ptep)
+ return __pte(0);
+ if (shift)
+ *pte_sizep = 1ul shift;
+ else
+ *pte_sizep = PAGE_SIZE;
+
+ if (ps *pte_sizep)
+ return __pte(0);
+
+ /* wait until _PAGE_BUSY is clear */
+ while (1) {
+ pte = pte_val(*ptep);
+ if (unlikely(pte _PAGE_BUSY)) {
+ cpu_relax();
+ continue;
+ }
What if we find a THP page that is splitting ? Older function returned
__pte(0) in that case.
+ }
+
+ /* If pte is not present return None */
+ if (unlikely(!(pte _PAGE_PRESENT)))
+ return __pte(0);
+
+ return pte;
+}
#endif /* __ASSEMBLY__ */
#endif /* __KERNEL__ */
--
-aneesh
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Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
Paul Mackerras pau...@samba.org writes: On Wed, Oct 09, 2013 at 12:47:31PM -0500, Scott Wood wrote: On Wed, 2013-10-09 at 03:48 -0500, Bhushan Bharat-R65777 wrote: What lookup_linux_pte_and_update() does:- - find_linux_pte_or_hugepte() - does size and some other trivial checks - Then atomically update the pte:- = while() = wait till _PAGE_BUSY is clear = atomically update the pte = if not updated then go back to while() above else break While what lookup_linux_pte() does:- - find_linux_pte_or_hugepte() - does size and some other trivial checks - wait till _PAGE_BUSY is clear - return pte I am finding it difficult to call lookup_linux_pte() from lookup_linux_pte_and_update(). You could factor out a common lookup_linux_ptep(). I don't really think it's enough code to be worth wringing out the last drop of duplication. However, if he removed the checks for _PAGE_BUSY and _PAGE_PRESENT as I suggested in another mail, and made it return the pte pointer rather than the value, it would then essentially be a lookup_linux_ptep() as you suggest. We also need to check for _PAGE_SPLITTING before going ahead and using the pte value -aneesh -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
Bharat Bhushan r65...@freescale.com writes:
We need to search linux pte to get pte attributes for
setting TLB in KVM.
This patch defines a linux_pte_lookup() function for same.
Signed-off-by: Bharat Bhushan bharat.bhus...@freescale.com
---
arch/powerpc/include/asm/pgtable.h | 35 +++
1 files changed, 35 insertions(+), 0 deletions(-)
diff --git a/arch/powerpc/include/asm/pgtable.h
b/arch/powerpc/include/asm/pgtable.h
index 7d6eacf..fd26c04 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -223,6 +223,41 @@ extern int gup_hugepte(pte_t *ptep, unsigned long sz,
unsigned long addr,
#endif
pte_t *find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea,
unsigned *shift);
+
+static inline pte_t lookup_linux_pte(pgd_t *pgdir, unsigned long hva,
+ unsigned long *pte_sizep)
+{
+ pte_t *ptep;
+ pte_t pte;
+ unsigned long ps = *pte_sizep;
+ unsigned int shift;
+
+ ptep = find_linux_pte_or_hugepte(pgdir, hva, shift);
+ if (!ptep)
+ return __pte(0);
+ if (shift)
+ *pte_sizep = 1ul shift;
+ else
+ *pte_sizep = PAGE_SIZE;
+
+ if (ps *pte_sizep)
+ return __pte(0);
+
+ /* wait until _PAGE_BUSY is clear */
+ while (1) {
+ pte = pte_val(*ptep);
+ if (unlikely(pte _PAGE_BUSY)) {
+ cpu_relax();
+ continue;
+ }
What if we find a THP page that is splitting ? Older function returned
__pte(0) in that case.
+ }
+
+ /* If pte is not present return None */
+ if (unlikely(!(pte _PAGE_PRESENT)))
+ return __pte(0);
+
+ return pte;
+}
#endif /* __ASSEMBLY__ */
#endif /* __KERNEL__ */
--
-aneesh
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Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
Paul Mackerras pau...@samba.org writes: On Wed, Oct 09, 2013 at 12:47:31PM -0500, Scott Wood wrote: On Wed, 2013-10-09 at 03:48 -0500, Bhushan Bharat-R65777 wrote: What lookup_linux_pte_and_update() does:- - find_linux_pte_or_hugepte() - does size and some other trivial checks - Then atomically update the pte:- = while() = wait till _PAGE_BUSY is clear = atomically update the pte = if not updated then go back to while() above else break While what lookup_linux_pte() does:- - find_linux_pte_or_hugepte() - does size and some other trivial checks - wait till _PAGE_BUSY is clear - return pte I am finding it difficult to call lookup_linux_pte() from lookup_linux_pte_and_update(). You could factor out a common lookup_linux_ptep(). I don't really think it's enough code to be worth wringing out the last drop of duplication. However, if he removed the checks for _PAGE_BUSY and _PAGE_PRESENT as I suggested in another mail, and made it return the pte pointer rather than the value, it would then essentially be a lookup_linux_ptep() as you suggest. We also need to check for _PAGE_SPLITTING before going ahead and using the pte value -aneesh -- To unsubscribe from this list: send the line unsubscribe kvm-ppc in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
On Tue, Oct 08, 2013 at 11:33:31AM +0530, Bharat Bhushan wrote:
We need to search linux pte to get pte attributes for
setting TLB in KVM.
This patch defines a linux_pte_lookup() function for same.
[snip]
+ /* wait until _PAGE_BUSY is clear */
+ while (1) {
+ pte = pte_val(*ptep);
+ if (unlikely(pte _PAGE_BUSY)) {
+ cpu_relax();
+ continue;
+ }
+ }
+
+ /* If pte is not present return None */
+ if (unlikely(!(pte _PAGE_PRESENT)))
+ return __pte(0);
First, this looks racy to me, since nothing stops the compiler
refetching pte from memory, and it might have become busy again in the
meantime.
However, I don't think you need to do any of this, since the caller in
your next patch checks for pte_present(pte) anyway. On book E systems
we don't use _PAGE_BUSY, so you don't need the loop for your intended
application. I suggest you remove the entire section quoted above.
Paul.
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Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
On Wed, Oct 09, 2013 at 12:47:31PM -0500, Scott Wood wrote: On Wed, 2013-10-09 at 03:48 -0500, Bhushan Bharat-R65777 wrote: What lookup_linux_pte_and_update() does:- - find_linux_pte_or_hugepte() - does size and some other trivial checks - Then atomically update the pte:- = while() = wait till _PAGE_BUSY is clear = atomically update the pte = if not updated then go back to while() above else break While what lookup_linux_pte() does:- - find_linux_pte_or_hugepte() - does size and some other trivial checks - wait till _PAGE_BUSY is clear - return pte I am finding it difficult to call lookup_linux_pte() from lookup_linux_pte_and_update(). You could factor out a common lookup_linux_ptep(). I don't really think it's enough code to be worth wringing out the last drop of duplication. However, if he removed the checks for _PAGE_BUSY and _PAGE_PRESENT as I suggested in another mail, and made it return the pte pointer rather than the value, it would then essentially be a lookup_linux_ptep() as you suggest. Paul. -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
-Original Message- From: Paul Mackerras [mailto:pau...@samba.org] Sent: Thursday, October 10, 2013 4:06 PM To: Wood Scott-B07421 Cc: Bhushan Bharat-R65777; Wood Scott-B07421; ag...@suse.de; Yoder Stuart- B08248; kvm@vger.kernel.org; kvm-...@vger.kernel.org Subject: Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function On Wed, Oct 09, 2013 at 12:47:31PM -0500, Scott Wood wrote: On Wed, 2013-10-09 at 03:48 -0500, Bhushan Bharat-R65777 wrote: What lookup_linux_pte_and_update() does:- - find_linux_pte_or_hugepte() - does size and some other trivial checks - Then atomically update the pte:- = while() = wait till _PAGE_BUSY is clear = atomically update the pte = if not updated then go back to while() above else break While what lookup_linux_pte() does:- - find_linux_pte_or_hugepte() - does size and some other trivial checks - wait till _PAGE_BUSY is clear - return pte I am finding it difficult to call lookup_linux_pte() from lookup_linux_pte_and_update(). You could factor out a common lookup_linux_ptep(). I don't really think it's enough code to be worth wringing out the last drop of duplication. However, if he removed the checks for _PAGE_BUSY and _PAGE_PRESENT as I suggested in another mail, and made it return the pte pointer rather than the value, it would then essentially be a lookup_linux_ptep() as you suggest. Do we want to have lookup_linux_pte() or lookup_linux_ptep() or both where lookup_linux_pte() and lookup_linux_pte_and_update() calls lookup_linux_ptep() ? -Bharat Paul. -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
On Thu, Oct 10, 2013 at 10:44:54AM +, Bhushan Bharat-R65777 wrote: -Original Message- From: Paul Mackerras [mailto:pau...@samba.org] Sent: Thursday, October 10, 2013 4:06 PM To: Wood Scott-B07421 Cc: Bhushan Bharat-R65777; Wood Scott-B07421; ag...@suse.de; Yoder Stuart- B08248; kvm@vger.kernel.org; kvm-...@vger.kernel.org Subject: Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function On Wed, Oct 09, 2013 at 12:47:31PM -0500, Scott Wood wrote: On Wed, 2013-10-09 at 03:48 -0500, Bhushan Bharat-R65777 wrote: What lookup_linux_pte_and_update() does:- - find_linux_pte_or_hugepte() - does size and some other trivial checks - Then atomically update the pte:- = while() = wait till _PAGE_BUSY is clear = atomically update the pte = if not updated then go back to while() above else break While what lookup_linux_pte() does:- - find_linux_pte_or_hugepte() - does size and some other trivial checks - wait till _PAGE_BUSY is clear - return pte I am finding it difficult to call lookup_linux_pte() from lookup_linux_pte_and_update(). You could factor out a common lookup_linux_ptep(). I don't really think it's enough code to be worth wringing out the last drop of duplication. However, if he removed the checks for _PAGE_BUSY and _PAGE_PRESENT as I suggested in another mail, and made it return the pte pointer rather than the value, it would then essentially be a lookup_linux_ptep() as you suggest. Do we want to have lookup_linux_pte() or lookup_linux_ptep() or both where lookup_linux_pte() and lookup_linux_pte_and_update() calls lookup_linux_ptep() ? I don't think we want both lookup_linux_pte() and lookup_linux_ptep(). Either have a lookup_linux_ptep() and call it from your book E code and from lookup_linux_pte_and_update(), or keep a separate lookup_linux_pte() and don't make the _and_update() version call it. I don't really care; you decide which looks nicer in the end. Of course someone will then tell you to do it the other way, but at that point it's just a matter of taste. Paul. -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
On Tue, Oct 08, 2013 at 11:33:31AM +0530, Bharat Bhushan wrote:
We need to search linux pte to get pte attributes for
setting TLB in KVM.
This patch defines a linux_pte_lookup() function for same.
[snip]
+ /* wait until _PAGE_BUSY is clear */
+ while (1) {
+ pte = pte_val(*ptep);
+ if (unlikely(pte _PAGE_BUSY)) {
+ cpu_relax();
+ continue;
+ }
+ }
+
+ /* If pte is not present return None */
+ if (unlikely(!(pte _PAGE_PRESENT)))
+ return __pte(0);
First, this looks racy to me, since nothing stops the compiler
refetching pte from memory, and it might have become busy again in the
meantime.
However, I don't think you need to do any of this, since the caller in
your next patch checks for pte_present(pte) anyway. On book E systems
we don't use _PAGE_BUSY, so you don't need the loop for your intended
application. I suggest you remove the entire section quoted above.
Paul.
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Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
On Wed, Oct 09, 2013 at 12:47:31PM -0500, Scott Wood wrote: On Wed, 2013-10-09 at 03:48 -0500, Bhushan Bharat-R65777 wrote: What lookup_linux_pte_and_update() does:- - find_linux_pte_or_hugepte() - does size and some other trivial checks - Then atomically update the pte:- = while() = wait till _PAGE_BUSY is clear = atomically update the pte = if not updated then go back to while() above else break While what lookup_linux_pte() does:- - find_linux_pte_or_hugepte() - does size and some other trivial checks - wait till _PAGE_BUSY is clear - return pte I am finding it difficult to call lookup_linux_pte() from lookup_linux_pte_and_update(). You could factor out a common lookup_linux_ptep(). I don't really think it's enough code to be worth wringing out the last drop of duplication. However, if he removed the checks for _PAGE_BUSY and _PAGE_PRESENT as I suggested in another mail, and made it return the pte pointer rather than the value, it would then essentially be a lookup_linux_ptep() as you suggest. Paul. -- To unsubscribe from this list: send the line unsubscribe kvm-ppc in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
-Original Message- From: Paul Mackerras [mailto:pau...@samba.org] Sent: Thursday, October 10, 2013 4:06 PM To: Wood Scott-B07421 Cc: Bhushan Bharat-R65777; Wood Scott-B07421; ag...@suse.de; Yoder Stuart- B08248; k...@vger.kernel.org; kvm-ppc@vger.kernel.org Subject: Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function On Wed, Oct 09, 2013 at 12:47:31PM -0500, Scott Wood wrote: On Wed, 2013-10-09 at 03:48 -0500, Bhushan Bharat-R65777 wrote: What lookup_linux_pte_and_update() does:- - find_linux_pte_or_hugepte() - does size and some other trivial checks - Then atomically update the pte:- = while() = wait till _PAGE_BUSY is clear = atomically update the pte = if not updated then go back to while() above else break While what lookup_linux_pte() does:- - find_linux_pte_or_hugepte() - does size and some other trivial checks - wait till _PAGE_BUSY is clear - return pte I am finding it difficult to call lookup_linux_pte() from lookup_linux_pte_and_update(). You could factor out a common lookup_linux_ptep(). I don't really think it's enough code to be worth wringing out the last drop of duplication. However, if he removed the checks for _PAGE_BUSY and _PAGE_PRESENT as I suggested in another mail, and made it return the pte pointer rather than the value, it would then essentially be a lookup_linux_ptep() as you suggest. Do we want to have lookup_linux_pte() or lookup_linux_ptep() or both where lookup_linux_pte() and lookup_linux_pte_and_update() calls lookup_linux_ptep() ? -Bharat Paul. -- To unsubscribe from this list: send the line unsubscribe kvm-ppc in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
On Thu, Oct 10, 2013 at 10:44:54AM +, Bhushan Bharat-R65777 wrote: -Original Message- From: Paul Mackerras [mailto:pau...@samba.org] Sent: Thursday, October 10, 2013 4:06 PM To: Wood Scott-B07421 Cc: Bhushan Bharat-R65777; Wood Scott-B07421; ag...@suse.de; Yoder Stuart- B08248; k...@vger.kernel.org; kvm-ppc@vger.kernel.org Subject: Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function On Wed, Oct 09, 2013 at 12:47:31PM -0500, Scott Wood wrote: On Wed, 2013-10-09 at 03:48 -0500, Bhushan Bharat-R65777 wrote: What lookup_linux_pte_and_update() does:- - find_linux_pte_or_hugepte() - does size and some other trivial checks - Then atomically update the pte:- = while() = wait till _PAGE_BUSY is clear = atomically update the pte = if not updated then go back to while() above else break While what lookup_linux_pte() does:- - find_linux_pte_or_hugepte() - does size and some other trivial checks - wait till _PAGE_BUSY is clear - return pte I am finding it difficult to call lookup_linux_pte() from lookup_linux_pte_and_update(). You could factor out a common lookup_linux_ptep(). I don't really think it's enough code to be worth wringing out the last drop of duplication. However, if he removed the checks for _PAGE_BUSY and _PAGE_PRESENT as I suggested in another mail, and made it return the pte pointer rather than the value, it would then essentially be a lookup_linux_ptep() as you suggest. Do we want to have lookup_linux_pte() or lookup_linux_ptep() or both where lookup_linux_pte() and lookup_linux_pte_and_update() calls lookup_linux_ptep() ? I don't think we want both lookup_linux_pte() and lookup_linux_ptep(). Either have a lookup_linux_ptep() and call it from your book E code and from lookup_linux_pte_and_update(), or keep a separate lookup_linux_pte() and don't make the _and_update() version call it. I don't really care; you decide which looks nicer in the end. Of course someone will then tell you to do it the other way, but at that point it's just a matter of taste. Paul. -- To unsubscribe from this list: send the line unsubscribe kvm-ppc in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
-Original Message-
From: Wood Scott-B07421
Sent: Wednesday, October 09, 2013 3:07 AM
To: Bhushan Bharat-R65777
Cc: ag...@suse.de; Yoder Stuart-B08248; kvm@vger.kernel.org; kvm-
p...@vger.kernel.org; pau...@samba.org; Bhushan Bharat-R65777
Subject: Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
On Tue, 2013-10-08 at 11:33 +0530, Bharat Bhushan wrote:
We need to search linux pte to get pte attributes for setting TLB
in KVM.
This patch defines a linux_pte_lookup() function for same.
Signed-off-by: Bharat Bhushan bharat.bhus...@freescale.com
---
arch/powerpc/include/asm/pgtable.h | 35
+++
1 files changed, 35 insertions(+), 0 deletions(-)
diff --git a/arch/powerpc/include/asm/pgtable.h
b/arch/powerpc/include/asm/pgtable.h
index 7d6eacf..fd26c04 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -223,6 +223,41 @@ extern int gup_hugepte(pte_t *ptep, unsigned long
sz, unsigned long addr, #endif pte_t
*find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea,
unsigned *shift);
+
+static inline pte_t lookup_linux_pte(pgd_t *pgdir, unsigned long hva,
+unsigned long *pte_sizep)
+{
+ pte_t *ptep;
+ pte_t pte;
+ unsigned long ps = *pte_sizep;
+ unsigned int shift;
+
+ ptep = find_linux_pte_or_hugepte(pgdir, hva, shift);
+ if (!ptep)
+ return __pte(0);
+ if (shift)
+ *pte_sizep = 1ul shift;
+ else
+ *pte_sizep = PAGE_SIZE;
+
+ if (ps *pte_sizep)
+ return __pte(0);
+
+ /* wait until _PAGE_BUSY is clear */
+ while (1) {
+ pte = pte_val(*ptep);
+ if (unlikely(pte _PAGE_BUSY)) {
+ cpu_relax();
+ continue;
+ }
+ }
+
+ /* If pte is not present return None */
+ if (unlikely(!(pte _PAGE_PRESENT)))
+ return __pte(0);
+
+ return pte;
+}
Can lookup_linux_pte_and_update() call lookup_linux_pte()?
What lookup_linux_pte_and_update() does:-
- find_linux_pte_or_hugepte()
- does size and some other trivial checks
- Then atomically update the pte:-
= while()
= wait till _PAGE_BUSY is clear
= atomically update the pte
= if not updated then go back to while() above else break
While what lookup_linux_pte() does:-
- find_linux_pte_or_hugepte()
- does size and some other trivial checks
- wait till _PAGE_BUSY is clear
- return pte
I am finding it difficult to call lookup_linux_pte() from
lookup_linux_pte_and_update().
Thanks
-Bharat
-Scott
Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
On Wed, 2013-10-09 at 03:48 -0500, Bhushan Bharat-R65777 wrote:
-Original Message-
From: Wood Scott-B07421
Sent: Wednesday, October 09, 2013 3:07 AM
To: Bhushan Bharat-R65777
Cc: ag...@suse.de; Yoder Stuart-B08248; kvm@vger.kernel.org; kvm-
p...@vger.kernel.org; pau...@samba.org; Bhushan Bharat-R65777
Subject: Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
On Tue, 2013-10-08 at 11:33 +0530, Bharat Bhushan wrote:
We need to search linux pte to get pte attributes for setting TLB
in KVM.
This patch defines a linux_pte_lookup() function for same.
Signed-off-by: Bharat Bhushan bharat.bhus...@freescale.com
---
arch/powerpc/include/asm/pgtable.h | 35
+++
1 files changed, 35 insertions(+), 0 deletions(-)
diff --git a/arch/powerpc/include/asm/pgtable.h
b/arch/powerpc/include/asm/pgtable.h
index 7d6eacf..fd26c04 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -223,6 +223,41 @@ extern int gup_hugepte(pte_t *ptep, unsigned long
sz, unsigned long addr, #endif pte_t
*find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea,
unsigned *shift);
+
+static inline pte_t lookup_linux_pte(pgd_t *pgdir, unsigned long hva,
+ unsigned long *pte_sizep)
+{
+ pte_t *ptep;
+ pte_t pte;
+ unsigned long ps = *pte_sizep;
+ unsigned int shift;
+
+ ptep = find_linux_pte_or_hugepte(pgdir, hva, shift);
+ if (!ptep)
+ return __pte(0);
+ if (shift)
+ *pte_sizep = 1ul shift;
+ else
+ *pte_sizep = PAGE_SIZE;
+
+ if (ps *pte_sizep)
+ return __pte(0);
+
+ /* wait until _PAGE_BUSY is clear */
+ while (1) {
+ pte = pte_val(*ptep);
+ if (unlikely(pte _PAGE_BUSY)) {
+ cpu_relax();
+ continue;
+ }
+ }
+
+ /* If pte is not present return None */
+ if (unlikely(!(pte _PAGE_PRESENT)))
+ return __pte(0);
+
+ return pte;
+}
Can lookup_linux_pte_and_update() call lookup_linux_pte()?
What lookup_linux_pte_and_update() does:-
- find_linux_pte_or_hugepte()
- does size and some other trivial checks
- Then atomically update the pte:-
= while()
= wait till _PAGE_BUSY is clear
= atomically update the pte
= if not updated then go back to while() above else break
While what lookup_linux_pte() does:-
- find_linux_pte_or_hugepte()
- does size and some other trivial checks
- wait till _PAGE_BUSY is clear
- return pte
I am finding it difficult to call lookup_linux_pte() from
lookup_linux_pte_and_update().
You could factor out a common lookup_linux_ptep().
-Scott
--
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the body of a message to majord...@vger.kernel.org
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RE: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
-Original Message-
From: Wood Scott-B07421
Sent: Wednesday, October 09, 2013 3:07 AM
To: Bhushan Bharat-R65777
Cc: ag...@suse.de; Yoder Stuart-B08248; k...@vger.kernel.org; kvm-
p...@vger.kernel.org; pau...@samba.org; Bhushan Bharat-R65777
Subject: Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
On Tue, 2013-10-08 at 11:33 +0530, Bharat Bhushan wrote:
We need to search linux pte to get pte attributes for setting TLB
in KVM.
This patch defines a linux_pte_lookup() function for same.
Signed-off-by: Bharat Bhushan bharat.bhus...@freescale.com
---
arch/powerpc/include/asm/pgtable.h | 35
+++
1 files changed, 35 insertions(+), 0 deletions(-)
diff --git a/arch/powerpc/include/asm/pgtable.h
b/arch/powerpc/include/asm/pgtable.h
index 7d6eacf..fd26c04 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -223,6 +223,41 @@ extern int gup_hugepte(pte_t *ptep, unsigned long
sz, unsigned long addr, #endif pte_t
*find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea,
unsigned *shift);
+
+static inline pte_t lookup_linux_pte(pgd_t *pgdir, unsigned long hva,
+unsigned long *pte_sizep)
+{
+ pte_t *ptep;
+ pte_t pte;
+ unsigned long ps = *pte_sizep;
+ unsigned int shift;
+
+ ptep = find_linux_pte_or_hugepte(pgdir, hva, shift);
+ if (!ptep)
+ return __pte(0);
+ if (shift)
+ *pte_sizep = 1ul shift;
+ else
+ *pte_sizep = PAGE_SIZE;
+
+ if (ps *pte_sizep)
+ return __pte(0);
+
+ /* wait until _PAGE_BUSY is clear */
+ while (1) {
+ pte = pte_val(*ptep);
+ if (unlikely(pte _PAGE_BUSY)) {
+ cpu_relax();
+ continue;
+ }
+ }
+
+ /* If pte is not present return None */
+ if (unlikely(!(pte _PAGE_PRESENT)))
+ return __pte(0);
+
+ return pte;
+}
Can lookup_linux_pte_and_update() call lookup_linux_pte()?
What lookup_linux_pte_and_update() does:-
- find_linux_pte_or_hugepte()
- does size and some other trivial checks
- Then atomically update the pte:-
= while()
= wait till _PAGE_BUSY is clear
= atomically update the pte
= if not updated then go back to while() above else break
While what lookup_linux_pte() does:-
- find_linux_pte_or_hugepte()
- does size and some other trivial checks
- wait till _PAGE_BUSY is clear
- return pte
I am finding it difficult to call lookup_linux_pte() from
lookup_linux_pte_and_update().
Thanks
-Bharat
-Scott
Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
On Wed, 2013-10-09 at 03:48 -0500, Bhushan Bharat-R65777 wrote:
-Original Message-
From: Wood Scott-B07421
Sent: Wednesday, October 09, 2013 3:07 AM
To: Bhushan Bharat-R65777
Cc: ag...@suse.de; Yoder Stuart-B08248; k...@vger.kernel.org; kvm-
p...@vger.kernel.org; pau...@samba.org; Bhushan Bharat-R65777
Subject: Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
On Tue, 2013-10-08 at 11:33 +0530, Bharat Bhushan wrote:
We need to search linux pte to get pte attributes for setting TLB
in KVM.
This patch defines a linux_pte_lookup() function for same.
Signed-off-by: Bharat Bhushan bharat.bhus...@freescale.com
---
arch/powerpc/include/asm/pgtable.h | 35
+++
1 files changed, 35 insertions(+), 0 deletions(-)
diff --git a/arch/powerpc/include/asm/pgtable.h
b/arch/powerpc/include/asm/pgtable.h
index 7d6eacf..fd26c04 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -223,6 +223,41 @@ extern int gup_hugepte(pte_t *ptep, unsigned long
sz, unsigned long addr, #endif pte_t
*find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea,
unsigned *shift);
+
+static inline pte_t lookup_linux_pte(pgd_t *pgdir, unsigned long hva,
+ unsigned long *pte_sizep)
+{
+ pte_t *ptep;
+ pte_t pte;
+ unsigned long ps = *pte_sizep;
+ unsigned int shift;
+
+ ptep = find_linux_pte_or_hugepte(pgdir, hva, shift);
+ if (!ptep)
+ return __pte(0);
+ if (shift)
+ *pte_sizep = 1ul shift;
+ else
+ *pte_sizep = PAGE_SIZE;
+
+ if (ps *pte_sizep)
+ return __pte(0);
+
+ /* wait until _PAGE_BUSY is clear */
+ while (1) {
+ pte = pte_val(*ptep);
+ if (unlikely(pte _PAGE_BUSY)) {
+ cpu_relax();
+ continue;
+ }
+ }
+
+ /* If pte is not present return None */
+ if (unlikely(!(pte _PAGE_PRESENT)))
+ return __pte(0);
+
+ return pte;
+}
Can lookup_linux_pte_and_update() call lookup_linux_pte()?
What lookup_linux_pte_and_update() does:-
- find_linux_pte_or_hugepte()
- does size and some other trivial checks
- Then atomically update the pte:-
= while()
= wait till _PAGE_BUSY is clear
= atomically update the pte
= if not updated then go back to while() above else break
While what lookup_linux_pte() does:-
- find_linux_pte_or_hugepte()
- does size and some other trivial checks
- wait till _PAGE_BUSY is clear
- return pte
I am finding it difficult to call lookup_linux_pte() from
lookup_linux_pte_and_update().
You could factor out a common lookup_linux_ptep().
-Scott
--
To unsubscribe from this list: send the line unsubscribe kvm-ppc in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
On Tue, 2013-10-08 at 11:33 +0530, Bharat Bhushan wrote:
We need to search linux pte to get pte attributes for
setting TLB in KVM.
This patch defines a linux_pte_lookup() function for same.
Signed-off-by: Bharat Bhushan bharat.bhus...@freescale.com
---
arch/powerpc/include/asm/pgtable.h | 35 +++
1 files changed, 35 insertions(+), 0 deletions(-)
diff --git a/arch/powerpc/include/asm/pgtable.h
b/arch/powerpc/include/asm/pgtable.h
index 7d6eacf..fd26c04 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -223,6 +223,41 @@ extern int gup_hugepte(pte_t *ptep, unsigned long sz,
unsigned long addr,
#endif
pte_t *find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea,
unsigned *shift);
+
+static inline pte_t lookup_linux_pte(pgd_t *pgdir, unsigned long hva,
+ unsigned long *pte_sizep)
+{
+ pte_t *ptep;
+ pte_t pte;
+ unsigned long ps = *pte_sizep;
+ unsigned int shift;
+
+ ptep = find_linux_pte_or_hugepte(pgdir, hva, shift);
+ if (!ptep)
+ return __pte(0);
+ if (shift)
+ *pte_sizep = 1ul shift;
+ else
+ *pte_sizep = PAGE_SIZE;
+
+ if (ps *pte_sizep)
+ return __pte(0);
+
+ /* wait until _PAGE_BUSY is clear */
+ while (1) {
+ pte = pte_val(*ptep);
+ if (unlikely(pte _PAGE_BUSY)) {
+ cpu_relax();
+ continue;
+ }
+ }
+
+ /* If pte is not present return None */
+ if (unlikely(!(pte _PAGE_PRESENT)))
+ return __pte(0);
+
+ return pte;
+}
Can lookup_linux_pte_and_update() call lookup_linux_pte()?
-Scott
--
To unsubscribe from this list: send the line unsubscribe kvm in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function
On Tue, 2013-10-08 at 11:33 +0530, Bharat Bhushan wrote:
We need to search linux pte to get pte attributes for
setting TLB in KVM.
This patch defines a linux_pte_lookup() function for same.
Signed-off-by: Bharat Bhushan bharat.bhus...@freescale.com
---
arch/powerpc/include/asm/pgtable.h | 35 +++
1 files changed, 35 insertions(+), 0 deletions(-)
diff --git a/arch/powerpc/include/asm/pgtable.h
b/arch/powerpc/include/asm/pgtable.h
index 7d6eacf..fd26c04 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -223,6 +223,41 @@ extern int gup_hugepte(pte_t *ptep, unsigned long sz,
unsigned long addr,
#endif
pte_t *find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea,
unsigned *shift);
+
+static inline pte_t lookup_linux_pte(pgd_t *pgdir, unsigned long hva,
+ unsigned long *pte_sizep)
+{
+ pte_t *ptep;
+ pte_t pte;
+ unsigned long ps = *pte_sizep;
+ unsigned int shift;
+
+ ptep = find_linux_pte_or_hugepte(pgdir, hva, shift);
+ if (!ptep)
+ return __pte(0);
+ if (shift)
+ *pte_sizep = 1ul shift;
+ else
+ *pte_sizep = PAGE_SIZE;
+
+ if (ps *pte_sizep)
+ return __pte(0);
+
+ /* wait until _PAGE_BUSY is clear */
+ while (1) {
+ pte = pte_val(*ptep);
+ if (unlikely(pte _PAGE_BUSY)) {
+ cpu_relax();
+ continue;
+ }
+ }
+
+ /* If pte is not present return None */
+ if (unlikely(!(pte _PAGE_PRESENT)))
+ return __pte(0);
+
+ return pte;
+}
Can lookup_linux_pte_and_update() call lookup_linux_pte()?
-Scott
--
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the body of a message to majord...@vger.kernel.org
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