Re: [tip:x86/asm] x86/asm: Add support for the pcommit instruction
On 02/24/2015 01:48 PM, Ross Zwisler wrote: > On Tue, 2015-02-24 at 13:41 -0800, H. Peter Anvin wrote: >> On 02/24/2015 01:40 PM, H. Peter Anvin wrote: >>> On 02/24/2015 01:30 AM, Borislav Petkov wrote: On Mon, Feb 23, 2015 at 03:14:01PM -0800, H. Peter Anvin wrote: > That may cause the same line to be flushed twice. I would suggest, > instead, also removing the arithmetic on void *: Btw, should we hold down all those suggested usages somewhere in Documentation/x86/ as commit messages are generally harder to find? >>> >>> Yes, and commit messages can't be corrected after the fact. >>> >> >> Either that, or perhaps even better in kerneldoc comments in the source >> itself. > > Either sounds like a good idea to me. :) Let me know which you'd prefer > and I'll get something written up. > Kerneldoc would be better, as it is more likely to be maintained in proximity for the source. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [tip:x86/asm] x86/asm: Add support for the pcommit instruction
On Tue, 2015-02-24 at 13:41 -0800, H. Peter Anvin wrote: > On 02/24/2015 01:40 PM, H. Peter Anvin wrote: > > On 02/24/2015 01:30 AM, Borislav Petkov wrote: > >> On Mon, Feb 23, 2015 at 03:14:01PM -0800, H. Peter Anvin wrote: > >>> That may cause the same line to be flushed twice. I would suggest, > >>> instead, also removing the arithmetic on void *: > >> > >> Btw, should we hold down all those suggested usages somewhere in > >> Documentation/x86/ as commit messages are generally harder to find? > >> > > > > Yes, and commit messages can't be corrected after the fact. > > > > Either that, or perhaps even better in kerneldoc comments in the source > itself. Either sounds like a good idea to me. :) Let me know which you'd prefer and I'll get something written up. - Ross -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [tip:x86/asm] x86/asm: Add support for the pcommit instruction
On 02/24/2015 01:40 PM, H. Peter Anvin wrote: > On 02/24/2015 01:30 AM, Borislav Petkov wrote: >> On Mon, Feb 23, 2015 at 03:14:01PM -0800, H. Peter Anvin wrote: >>> That may cause the same line to be flushed twice. I would suggest, >>> instead, also removing the arithmetic on void *: >> >> Btw, should we hold down all those suggested usages somewhere in >> Documentation/x86/ as commit messages are generally harder to find? >> > > Yes, and commit messages can't be corrected after the fact. > Either that, or perhaps even better in kerneldoc comments in the source itself. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [tip:x86/asm] x86/asm: Add support for the pcommit instruction
On 02/24/2015 01:30 AM, Borislav Petkov wrote: > On Mon, Feb 23, 2015 at 03:14:01PM -0800, H. Peter Anvin wrote: >> That may cause the same line to be flushed twice. I would suggest, >> instead, also removing the arithmetic on void *: > > Btw, should we hold down all those suggested usages somewhere in > Documentation/x86/ as commit messages are generally harder to find? > Yes, and commit messages can't be corrected after the fact. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [tip:x86/asm] x86/asm: Add support for the pcommit instruction
On Mon, Feb 23, 2015 at 03:14:01PM -0800, H. Peter Anvin wrote: > That may cause the same line to be flushed twice. I would suggest, > instead, also removing the arithmetic on void *: Btw, should we hold down all those suggested usages somewhere in Documentation/x86/ as commit messages are generally harder to find? -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [tip:x86/asm] x86/asm: Add support for the pcommit instruction
On 02/24/2015 01:40 PM, H. Peter Anvin wrote: On 02/24/2015 01:30 AM, Borislav Petkov wrote: On Mon, Feb 23, 2015 at 03:14:01PM -0800, H. Peter Anvin wrote: That may cause the same line to be flushed twice. I would suggest, instead, also removing the arithmetic on void *: Btw, should we hold down all those suggested usages somewhere in Documentation/x86/ as commit messages are generally harder to find? Yes, and commit messages can't be corrected after the fact. Either that, or perhaps even better in kerneldoc comments in the source itself. -hpa -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [tip:x86/asm] x86/asm: Add support for the pcommit instruction
On 02/24/2015 01:30 AM, Borislav Petkov wrote: On Mon, Feb 23, 2015 at 03:14:01PM -0800, H. Peter Anvin wrote: That may cause the same line to be flushed twice. I would suggest, instead, also removing the arithmetic on void *: Btw, should we hold down all those suggested usages somewhere in Documentation/x86/ as commit messages are generally harder to find? Yes, and commit messages can't be corrected after the fact. -hpa -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [tip:x86/asm] x86/asm: Add support for the pcommit instruction
On 02/24/2015 01:48 PM, Ross Zwisler wrote: On Tue, 2015-02-24 at 13:41 -0800, H. Peter Anvin wrote: On 02/24/2015 01:40 PM, H. Peter Anvin wrote: On 02/24/2015 01:30 AM, Borislav Petkov wrote: On Mon, Feb 23, 2015 at 03:14:01PM -0800, H. Peter Anvin wrote: That may cause the same line to be flushed twice. I would suggest, instead, also removing the arithmetic on void *: Btw, should we hold down all those suggested usages somewhere in Documentation/x86/ as commit messages are generally harder to find? Yes, and commit messages can't be corrected after the fact. Either that, or perhaps even better in kerneldoc comments in the source itself. Either sounds like a good idea to me. :) Let me know which you'd prefer and I'll get something written up. Kerneldoc would be better, as it is more likely to be maintained in proximity for the source. -hpa -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [tip:x86/asm] x86/asm: Add support for the pcommit instruction
On Tue, 2015-02-24 at 13:41 -0800, H. Peter Anvin wrote: On 02/24/2015 01:40 PM, H. Peter Anvin wrote: On 02/24/2015 01:30 AM, Borislav Petkov wrote: On Mon, Feb 23, 2015 at 03:14:01PM -0800, H. Peter Anvin wrote: That may cause the same line to be flushed twice. I would suggest, instead, also removing the arithmetic on void *: Btw, should we hold down all those suggested usages somewhere in Documentation/x86/ as commit messages are generally harder to find? Yes, and commit messages can't be corrected after the fact. Either that, or perhaps even better in kerneldoc comments in the source itself. Either sounds like a good idea to me. :) Let me know which you'd prefer and I'll get something written up. - Ross -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [tip:x86/asm] x86/asm: Add support for the pcommit instruction
On Mon, Feb 23, 2015 at 03:14:01PM -0800, H. Peter Anvin wrote: That may cause the same line to be flushed twice. I would suggest, instead, also removing the arithmetic on void *: Btw, should we hold down all those suggested usages somewhere in Documentation/x86/ as commit messages are generally harder to find? -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [tip:x86/asm] x86/asm: Add support for the pcommit instruction
On 02/20/2015 02:31 AM, tip-bot for Ross Zwisler wrote:
>
> This function shows how to properly use clwb/clflushopt/clflush
> and pcommit with appropriate fencing:
>
> void flush_and_commit_buffer(void *vaddr, unsigned int size)
> {
> void *vend = vaddr + size - 1;
>
> for (; vaddr < vend; vaddr += boot_cpu_data.x86_clflush_size)
> clwb(vaddr);
>
> /* Flush any possible final partial cacheline */
> clwb(vend);
>
> /*
>* sfence to order clwb/clflushopt/clflush cache flushes
>* mfence via mb() also works
>*/
> wmb();
>
> /* pcommit and the required sfence for ordering */
> pcommit_sfence();
> }
>
That may cause the same line to be flushed twice. I would suggest,
instead, also removing the arithmetic on void *:
Totally untested, yadda yadda...
void flush_and_commit_buffer(void *vaddr, unsigned int size)
{
unsigned long clflush_mask = boot_cpu_data.x86_clflush_size - 1;
char *vend = (char *)vaddr + size;
char *p;
for (p = (char *)((unsigned long)vaddr & ~clflush_mask);
p < vend; p += boot_cpu_data.x86_clflush_size)
clwb(vaddr);
/*
* sfence to order clwb/clflushopt/clflush cache flushes
* mfence via mb() also works
*/
wmb();
/* pcommit and the required sfence for ordering */
pcommit_sfence();
}
--
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the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [tip:x86/asm] x86/asm: Add support for the pcommit instruction
On 02/20/2015 02:31 AM, tip-bot for Ross Zwisler wrote:
This function shows how to properly use clwb/clflushopt/clflush
and pcommit with appropriate fencing:
void flush_and_commit_buffer(void *vaddr, unsigned int size)
{
void *vend = vaddr + size - 1;
for (; vaddr vend; vaddr += boot_cpu_data.x86_clflush_size)
clwb(vaddr);
/* Flush any possible final partial cacheline */
clwb(vend);
/*
* sfence to order clwb/clflushopt/clflush cache flushes
* mfence via mb() also works
*/
wmb();
/* pcommit and the required sfence for ordering */
pcommit_sfence();
}
That may cause the same line to be flushed twice. I would suggest,
instead, also removing the arithmetic on void *:
Totally untested, yadda yadda...
void flush_and_commit_buffer(void *vaddr, unsigned int size)
{
unsigned long clflush_mask = boot_cpu_data.x86_clflush_size - 1;
char *vend = (char *)vaddr + size;
char *p;
for (p = (char *)((unsigned long)vaddr ~clflush_mask);
p vend; p += boot_cpu_data.x86_clflush_size)
clwb(vaddr);
/*
* sfence to order clwb/clflushopt/clflush cache flushes
* mfence via mb() also works
*/
wmb();
/* pcommit and the required sfence for ordering */
pcommit_sfence();
}
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[tip:x86/asm] x86/asm: Add support for the pcommit instruction
Commit-ID: 719d359dc7b6be3e43d6661f192ceb980b10ee26
Gitweb: http://git.kernel.org/tip/719d359dc7b6be3e43d6661f192ceb980b10ee26
Author: Ross Zwisler
AuthorDate: Thu, 19 Feb 2015 10:37:28 -0700
Committer: Ingo Molnar
CommitDate: Fri, 20 Feb 2015 09:43:36 +0100
x86/asm: Add support for the pcommit instruction
Add support for the new pcommit (persistent commit) instruction.
This instruction was announced in the document "Intel
Architecture Instruction Set Extensions Programming Reference"
with reference number 319433-022:
https://software.intel.com/sites/default/files/managed/0d/53/319433-022.pdf
The pcommit instruction ensures that data that has been flushed
from the processor's cache hierarchy with clwb, clflushopt or
clflush is accepted to memory and is durable on the DIMM. The
primary use case for this is persistent memory.
This function shows how to properly use clwb/clflushopt/clflush
and pcommit with appropriate fencing:
void flush_and_commit_buffer(void *vaddr, unsigned int size)
{
void *vend = vaddr + size - 1;
for (; vaddr < vend; vaddr += boot_cpu_data.x86_clflush_size)
clwb(vaddr);
/* Flush any possible final partial cacheline */
clwb(vend);
/*
* sfence to order clwb/clflushopt/clflush cache flushes
* mfence via mb() also works
*/
wmb();
/* pcommit and the required sfence for ordering */
pcommit_sfence();
}
After this function completes the data pointed to by vaddr is
has been accepted to memory and will be durable if the vaddr
points to persistent memory.
Pcommit must always be ordered by an mfence or sfence, so to
help simplify things we include both the pcommit and the
required sfence in the alternatives generated by
pcommit_sfence(). The other option is to keep them separated,
but on platforms that don't support pcommit this would then turn
into:
void flush_and_commit_buffer(void *vaddr, unsigned int size)
{
void *vend = vaddr + size - 1;
for (; vaddr < vend; vaddr += boot_cpu_data.x86_clflush_size)
clwb(vaddr);
/* Flush any possible final partial cacheline */
clwb(vend);
/*
* sfence to order clwb/clflushopt/clflush cache flushes
* mfence via mb() also works
*/
wmb();
nop(); /* from pcommit(), via alternatives */
/*
* sfence to order pcommit
* mfence via mb() also works
*/
wmb();
}
This is still correct, but now you've got two fences separated
by only a nop. With the commit and the fence together in
pcommit_sfence() you avoid the final unneeded fence.
Signed-off-by: Ross Zwisler
Acked-by: Borislav Petkov
Acked-by: H. Peter Anvin
Cc: Linus Torvalds
Cc: Thomas Gleixner
Link:
http://lkml.kernel.org/r/1424367448-24254-1-git-send-email-ross.zwis...@linux.intel.com
Signed-off-by: Ingo Molnar
---
arch/x86/include/asm/cpufeature.h| 1 +
arch/x86/include/asm/special_insns.h | 10 ++
2 files changed, 11 insertions(+)
diff --git a/arch/x86/include/asm/cpufeature.h
b/arch/x86/include/asm/cpufeature.h
index 90a5485..d6428ea 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -231,6 +231,7 @@
#define X86_FEATURE_RDSEED ( 9*32+18) /* The RDSEED instruction */
#define X86_FEATURE_ADX( 9*32+19) /* The ADCX and ADOX
instructions */
#define X86_FEATURE_SMAP ( 9*32+20) /* Supervisor Mode Access Prevention
*/
+#define X86_FEATURE_PCOMMIT( 9*32+22) /* PCOMMIT instruction */
#define X86_FEATURE_CLFLUSHOPT ( 9*32+23) /* CLFLUSHOPT instruction */
#define X86_FEATURE_AVX512PF ( 9*32+26) /* AVX-512 Prefetch */
#define X86_FEATURE_AVX512ER ( 9*32+27) /* AVX-512 Exponential and
Reciprocal */
diff --git a/arch/x86/include/asm/special_insns.h
b/arch/x86/include/asm/special_insns.h
index e820c08..0962501 100644
--- a/arch/x86/include/asm/special_insns.h
+++ b/arch/x86/include/asm/special_insns.h
@@ -4,6 +4,8 @@
#ifdef __KERNEL__
+#include
+
static inline void native_clts(void)
{
asm volatile("clts");
@@ -199,6 +201,14 @@ static inline void clflushopt(volatile void *__p)
"+m" (*(volatile char __force *)__p));
}
+static inline void pcommit_sfence(void)
+{
+ alternative(ASM_NOP7,
+ ".byte 0x66, 0x0f, 0xae, 0xf8\n\t" /* pcommit */
+ "sfence",
+ X86_FEATURE_PCOMMIT);
+}
+
#define nop() asm volatile ("nop")
--
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[tip:x86/asm] x86/asm: Add support for the pcommit instruction
Commit-ID: 719d359dc7b6be3e43d6661f192ceb980b10ee26
Gitweb: http://git.kernel.org/tip/719d359dc7b6be3e43d6661f192ceb980b10ee26
Author: Ross Zwisler ross.zwis...@linux.intel.com
AuthorDate: Thu, 19 Feb 2015 10:37:28 -0700
Committer: Ingo Molnar mi...@kernel.org
CommitDate: Fri, 20 Feb 2015 09:43:36 +0100
x86/asm: Add support for the pcommit instruction
Add support for the new pcommit (persistent commit) instruction.
This instruction was announced in the document Intel
Architecture Instruction Set Extensions Programming Reference
with reference number 319433-022:
https://software.intel.com/sites/default/files/managed/0d/53/319433-022.pdf
The pcommit instruction ensures that data that has been flushed
from the processor's cache hierarchy with clwb, clflushopt or
clflush is accepted to memory and is durable on the DIMM. The
primary use case for this is persistent memory.
This function shows how to properly use clwb/clflushopt/clflush
and pcommit with appropriate fencing:
void flush_and_commit_buffer(void *vaddr, unsigned int size)
{
void *vend = vaddr + size - 1;
for (; vaddr vend; vaddr += boot_cpu_data.x86_clflush_size)
clwb(vaddr);
/* Flush any possible final partial cacheline */
clwb(vend);
/*
* sfence to order clwb/clflushopt/clflush cache flushes
* mfence via mb() also works
*/
wmb();
/* pcommit and the required sfence for ordering */
pcommit_sfence();
}
After this function completes the data pointed to by vaddr is
has been accepted to memory and will be durable if the vaddr
points to persistent memory.
Pcommit must always be ordered by an mfence or sfence, so to
help simplify things we include both the pcommit and the
required sfence in the alternatives generated by
pcommit_sfence(). The other option is to keep them separated,
but on platforms that don't support pcommit this would then turn
into:
void flush_and_commit_buffer(void *vaddr, unsigned int size)
{
void *vend = vaddr + size - 1;
for (; vaddr vend; vaddr += boot_cpu_data.x86_clflush_size)
clwb(vaddr);
/* Flush any possible final partial cacheline */
clwb(vend);
/*
* sfence to order clwb/clflushopt/clflush cache flushes
* mfence via mb() also works
*/
wmb();
nop(); /* from pcommit(), via alternatives */
/*
* sfence to order pcommit
* mfence via mb() also works
*/
wmb();
}
This is still correct, but now you've got two fences separated
by only a nop. With the commit and the fence together in
pcommit_sfence() you avoid the final unneeded fence.
Signed-off-by: Ross Zwisler ross.zwis...@linux.intel.com
Acked-by: Borislav Petkov b...@suse.de
Acked-by: H. Peter Anvin h...@linux.intel.com
Cc: Linus Torvalds torva...@linux-foundation.org
Cc: Thomas Gleixner t...@linutronix.de
Link:
http://lkml.kernel.org/r/1424367448-24254-1-git-send-email-ross.zwis...@linux.intel.com
Signed-off-by: Ingo Molnar mi...@kernel.org
---
arch/x86/include/asm/cpufeature.h| 1 +
arch/x86/include/asm/special_insns.h | 10 ++
2 files changed, 11 insertions(+)
diff --git a/arch/x86/include/asm/cpufeature.h
b/arch/x86/include/asm/cpufeature.h
index 90a5485..d6428ea 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -231,6 +231,7 @@
#define X86_FEATURE_RDSEED ( 9*32+18) /* The RDSEED instruction */
#define X86_FEATURE_ADX( 9*32+19) /* The ADCX and ADOX
instructions */
#define X86_FEATURE_SMAP ( 9*32+20) /* Supervisor Mode Access Prevention
*/
+#define X86_FEATURE_PCOMMIT( 9*32+22) /* PCOMMIT instruction */
#define X86_FEATURE_CLFLUSHOPT ( 9*32+23) /* CLFLUSHOPT instruction */
#define X86_FEATURE_AVX512PF ( 9*32+26) /* AVX-512 Prefetch */
#define X86_FEATURE_AVX512ER ( 9*32+27) /* AVX-512 Exponential and
Reciprocal */
diff --git a/arch/x86/include/asm/special_insns.h
b/arch/x86/include/asm/special_insns.h
index e820c08..0962501 100644
--- a/arch/x86/include/asm/special_insns.h
+++ b/arch/x86/include/asm/special_insns.h
@@ -4,6 +4,8 @@
#ifdef __KERNEL__
+#include asm/nops.h
+
static inline void native_clts(void)
{
asm volatile(clts);
@@ -199,6 +201,14 @@ static inline void clflushopt(volatile void *__p)
+m (*(volatile char __force *)__p));
}
+static inline void pcommit_sfence(void)
+{
+ alternative(ASM_NOP7,
+ .byte 0x66, 0x0f, 0xae, 0xf8\n\t /* pcommit */
+ sfence,
+ X86_FEATURE_PCOMMIT);
+}
+
#define nop() asm volatile (nop)
--
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