RE: [PATCH 5/6 v5] kvm: booke: clear host tlb reference flag on guest tlb invalidation
-Original Message- From: Wood Scott-B07421 Sent: Friday, September 20, 2013 11:38 PM To: Bhushan Bharat-R65777 Cc: Wood Scott-B07421; b...@kernel.crashing.org; ag...@suse.de; pau...@samba.org; k...@vger.kernel.org; kvm-ppc@vger.kernel.org; linuxppc- d...@lists.ozlabs.org Subject: Re: [PATCH 5/6 v5] kvm: booke: clear host tlb reference flag on guest tlb invalidation On Fri, 2013-09-20 at 13:04 -0500, Bhushan Bharat-R65777 wrote: -Original Message- From: Wood Scott-B07421 Sent: Friday, September 20, 2013 9:48 PM To: Bhushan Bharat-R65777 Cc: Wood Scott-B07421; b...@kernel.crashing.org; ag...@suse.de; pau...@samba.org; k...@vger.kernel.org; kvm-ppc@vger.kernel.org; linuxppc- d...@lists.ozlabs.org Subject: Re: [PATCH 5/6 v5] kvm: booke: clear host tlb reference flag on guest tlb invalidation On Thu, 2013-09-19 at 23:19 -0500, Bhushan Bharat-R65777 wrote: We uses these bit flags only for TLB1 and if size of stlbe is 4K then we set E500_TLB_TLB0 otherwise we set E500_TLB_BITMAP. Although I think that E500_TLB_BITMAP should be set only if stlbe size is less than gtlbe size. Why? Even if there's only one bit set in the map, we need it to keep track of which entry was used. If there is one entry then will not this be simple/faster to not lookup bitmap and guest-host array? A flag indicate it is 1:1 map and this is physical address. The difference would be negligible, and you'd have added overhead (both runtime and complexity) of making this a special case. May be you are right , I will see if I can give a try :) BTW I have already sent v6 of this patch. -Bharat -Scott
RE: [PATCH 5/6 v5] kvm: booke: clear host tlb reference flag on guest tlb invalidation
-Original Message-
From: Wood Scott-B07421
Sent: Friday, September 20, 2013 9:48 PM
To: Bhushan Bharat-R65777
Cc: Wood Scott-B07421; b...@kernel.crashing.org; ag...@suse.de;
pau...@samba.org; k...@vger.kernel.org; kvm-ppc@vger.kernel.org; linuxppc-
d...@lists.ozlabs.org
Subject: Re: [PATCH 5/6 v5] kvm: booke: clear host tlb reference flag on guest
tlb invalidation
On Thu, 2013-09-19 at 23:19 -0500, Bhushan Bharat-R65777 wrote:
-Original Message-
From: Wood Scott-B07421
Sent: Friday, September 20, 2013 2:38 AM
To: Bhushan Bharat-R65777
Cc: b...@kernel.crashing.org; ag...@suse.de; pau...@samba.org;
k...@vger.kernel.org; kvm-ppc@vger.kernel.org;
linuxppc-...@lists.ozlabs.org; Bhushan Bharat-R65777
Subject: Re: [PATCH 5/6 v5] kvm: booke: clear host tlb reference
flag on guest tlb invalidation
This breaks when you have both E500_TLB_BITMAP and E500_TLB_TLB0 set.
I do not see any case where we set both E500_TLB_BITMAP and
E500_TLB_TLB0.
This would happen if you have a guest TLB1 entry that is backed by some 4K
pages
and some larger pages (e.g. if the guest maps CCSR with one big
TLB1 and there are varying I/O passthrough regions mapped). It's not common,
but it's possible.
Agree
Also we have not optimized that yet (keeping track of multiple shadow
TLB0 entries for one guest TLB1 entry)
This is about correctness, not optimization.
We uses these bit flags only for TLB1 and if size of stlbe is 4K then
we set E500_TLB_TLB0 otherwise we set E500_TLB_BITMAP. Although I
think that E500_TLB_BITMAP should be set only if stlbe size is less
than gtlbe size.
Why? Even if there's only one bit set in the map, we need it to keep track of
which entry was used.
If there is one entry then will not this be simple/faster to not lookup bitmap
and guest-host array?
A flag indicate it is 1:1 map and this is physical address.
-Bharat
-Scott
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Re: [PATCH 5/6 v5] kvm: booke: clear host tlb reference flag on guest tlb invalidation
On Fri, 2013-09-20 at 13:04 -0500, Bhushan Bharat-R65777 wrote: -Original Message- From: Wood Scott-B07421 Sent: Friday, September 20, 2013 9:48 PM To: Bhushan Bharat-R65777 Cc: Wood Scott-B07421; b...@kernel.crashing.org; ag...@suse.de; pau...@samba.org; k...@vger.kernel.org; kvm-ppc@vger.kernel.org; linuxppc- d...@lists.ozlabs.org Subject: Re: [PATCH 5/6 v5] kvm: booke: clear host tlb reference flag on guest tlb invalidation On Thu, 2013-09-19 at 23:19 -0500, Bhushan Bharat-R65777 wrote: We uses these bit flags only for TLB1 and if size of stlbe is 4K then we set E500_TLB_TLB0 otherwise we set E500_TLB_BITMAP. Although I think that E500_TLB_BITMAP should be set only if stlbe size is less than gtlbe size. Why? Even if there's only one bit set in the map, we need it to keep track of which entry was used. If there is one entry then will not this be simple/faster to not lookup bitmap and guest-host array? A flag indicate it is 1:1 map and this is physical address. The difference would be negligible, and you'd have added overhead (both runtime and complexity) of making this a special case. -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 5/6 v5] kvm: booke: clear host tlb reference flag on guest tlb invalidation
On Thu, 2013-09-19 at 11:32 +0530, Bharat Bhushan wrote: On booke, struct tlbe_ref contains host tlb mapping information (pfn: for guest-pfn to pfn, flags: attribute associated with this mapping) for a guest tlb entry. So when a guest creates a TLB entry then struct tlbe_ref is set to point to valid pfn and set attributes in flags field of the above said structure. When a guest TLB entry is invalidated then flags field of corresponding struct tlbe_ref is updated to point that this is no more valid, also we selectively clear some other attribute bits, example: if E500_TLB_BITMAP was set then we clear E500_TLB_BITMAP, if E500_TLB_TLB0 is set then we clear this. Ideally we should clear complete flags as this entry is invalid and does not have anything to re-used. The other part of the problem is that when we use the same entry again then also we do not clear (started doing or-ing etc). So far it was working because the selectively clearing mentioned above actually clears flags what was set during TLB mapping. But the problem starts coming when we add more attributes to this then we need to selectively clear them and which is not needed. This patch we do both - Clear flags when invalidating; - Clear flags when reusing same entry later Signed-off-by: Bharat Bhushan bharat.bhus...@freescale.com --- v3- v5 - New patch (found this issue when doing vfio-pci development) arch/powerpc/kvm/e500_mmu_host.c | 12 +++- 1 files changed, 7 insertions(+), 5 deletions(-) diff --git a/arch/powerpc/kvm/e500_mmu_host.c b/arch/powerpc/kvm/e500_mmu_host.c index 1c6a9d7..60f5a3c 100644 --- a/arch/powerpc/kvm/e500_mmu_host.c +++ b/arch/powerpc/kvm/e500_mmu_host.c @@ -217,7 +217,8 @@ void inval_gtlbe_on_host(struct kvmppc_vcpu_e500 *vcpu_e500, int tlbsel, } mb(); vcpu_e500-g2h_tlb1_map[esel] = 0; - ref-flags = ~(E500_TLB_BITMAP | E500_TLB_VALID); + /* Clear flags as TLB is not backed by the host anymore */ + ref-flags = 0; local_irq_restore(flags); } This breaks when you have both E500_TLB_BITMAP and E500_TLB_TLB0 set. Instead, just convert the final E500_TLB_VALID clearing at the end into ref-flags = 0, and convert the early return a few lines earlier into conditional execution of the tlbil_one(). -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 5/6 v5] kvm: booke: clear host tlb reference flag on guest tlb invalidation
-Original Message-
From: Wood Scott-B07421
Sent: Friday, September 20, 2013 2:38 AM
To: Bhushan Bharat-R65777
Cc: b...@kernel.crashing.org; ag...@suse.de; pau...@samba.org;
k...@vger.kernel.org; kvm-ppc@vger.kernel.org; linuxppc-...@lists.ozlabs.org;
Bhushan Bharat-R65777
Subject: Re: [PATCH 5/6 v5] kvm: booke: clear host tlb reference flag on guest
tlb invalidation
On Thu, 2013-09-19 at 11:32 +0530, Bharat Bhushan wrote:
On booke, struct tlbe_ref contains host tlb mapping information
(pfn: for guest-pfn to pfn, flags: attribute associated with this
mapping) for a guest tlb entry. So when a guest creates a TLB entry
then struct tlbe_ref is set to point to valid pfn and set
attributes in flags field of the above said structure. When a guest
TLB entry is invalidated then flags field of corresponding struct
tlbe_ref is updated to point that this is no more valid, also we
selectively clear some other attribute bits, example: if
E500_TLB_BITMAP was set then we clear E500_TLB_BITMAP, if E500_TLB_TLB0 is
set
then we clear this.
Ideally we should clear complete flags as this entry is invalid and
does not have anything to re-used. The other part of the problem is
that when we use the same entry again then also we do not clear (started
doing
or-ing etc).
So far it was working because the selectively clearing mentioned above
actually clears flags what was set during TLB mapping. But the
problem starts coming when we add more attributes to this then we need
to selectively clear them and which is not needed.
This patch we do both
- Clear flags when invalidating;
- Clear flags when reusing same entry later
Signed-off-by: Bharat Bhushan bharat.bhus...@freescale.com
---
v3- v5
- New patch (found this issue when doing vfio-pci development)
arch/powerpc/kvm/e500_mmu_host.c | 12 +++-
1 files changed, 7 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/kvm/e500_mmu_host.c
b/arch/powerpc/kvm/e500_mmu_host.c
index 1c6a9d7..60f5a3c 100644
--- a/arch/powerpc/kvm/e500_mmu_host.c
+++ b/arch/powerpc/kvm/e500_mmu_host.c
@@ -217,7 +217,8 @@ void inval_gtlbe_on_host(struct kvmppc_vcpu_e500
*vcpu_e500, int tlbsel,
}
mb();
vcpu_e500-g2h_tlb1_map[esel] = 0;
- ref-flags = ~(E500_TLB_BITMAP | E500_TLB_VALID);
+ /* Clear flags as TLB is not backed by the host anymore */
+ ref-flags = 0;
local_irq_restore(flags);
}
This breaks when you have both E500_TLB_BITMAP and E500_TLB_TLB0 set.
I do not see any case where we set both E500_TLB_BITMAP and E500_TLB_TLB0. Also
we have not optimized that yet (keeping track of multiple shadow TLB0 entries
for one guest TLB1 entry)
We uses these bit flags only for TLB1 and if size of stlbe is 4K then we set
E500_TLB_TLB0 otherwise we set E500_TLB_BITMAP. Although I think that
E500_TLB_BITMAP should be set only if stlbe size is less than gtlbe size.
Instead, just convert the final E500_TLB_VALID clearing at the end into
ref-flags = 0, and convert the early return a few lines earlier into
conditional execution of the tlbil_one().
This looks better, will send the patch shortly.
Thanks
-Bharat
-Scott
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