The HRESET instruction isolates the classification of individual
tasks when they run sequentially on the same logical processor. It resets
the classification history that the logical processor maintains.

Cc: Len Brown <len.brown@intel.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com>
Cc: Zhao Liu <zhao1.liu@linux.intel.com>
Cc: Zhuocheng Ding <zhuocheng.ding@intel.com>
Cc: x86@kernel.org
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
Patch cherry-picked from the IPC classes patchset.
---
---
 arch/x86/include/asm/cpufeatures.h | 1 +
 arch/x86/include/asm/msr-index.h   | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 8104f4791abd..3b42479c049d 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -326,6 +326,7 @@
 #define X86_FEATURE_FSRC		(12*32+12) /* "" Fast short REP {CMPSB,SCASB} */
 #define X86_FEATURE_LKGS		(12*32+18) /* "" Load "kernel" (userspace) GS */
 #define X86_FEATURE_AMX_FP16		(12*32+21) /* "" AMX fp16 Support */
+#define X86_FEATURE_HRESET		(12*32+22) /* Hardware history reset instruction */
 #define X86_FEATURE_AVX_IFMA            (12*32+23) /* "" Support for VPMADD52[H,L]UQ */
 #define X86_FEATURE_LAM			(12*32+26) /* Linear Address Masking */
 
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index d74932a0778d..65b1bfb9c304 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -1155,6 +1155,9 @@
 
 #define MSR_IA32_HW_FEEDBACK_CHAR       0x17d2
 
+/* Hardware History Reset  */
+#define MSR_IA32_HW_HRESET_ENABLE	0x17da
+
 /* x2APIC locked status */
 #define MSR_IA32_XAPIC_DISABLE_STATUS	0xBD
 #define LEGACY_XAPIC_DISABLED		BIT(0) /*
-- 
2.25.1

On Fri, Feb 02, 2024 at 08:05:13PM -0800, Ricardo Neri wrote:
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index 8104f4791abd..3b42479c049d 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -326,6 +326,7 @@
>  #define X86_FEATURE_FSRC		(12*32+12) /* "" Fast short REP {CMPSB,SCASB} */
>  #define X86_FEATURE_LKGS		(12*32+18) /* "" Load "kernel" (userspace) GS */
>  #define X86_FEATURE_AMX_FP16		(12*32+21) /* "" AMX fp16 Support */
> +#define X86_FEATURE_HRESET		(12*32+22) /* Hardware history reset instruction */

  #define X86_FEATURE_HRESET		(12*32+22) /* "" Hardware history reset instruction */

unless this really needs to be visible in /proc/cpuinfo:

Documentation/arch/x86/cpuinfo.rst

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

On Sat, Feb 03, 2024 at 10:36:22AM +0100, Borislav Petkov wrote:
> On Fri, Feb 02, 2024 at 08:05:13PM -0800, Ricardo Neri wrote:
> > diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> > index 8104f4791abd..3b42479c049d 100644
> > --- a/arch/x86/include/asm/cpufeatures.h
> > +++ b/arch/x86/include/asm/cpufeatures.h
> > @@ -326,6 +326,7 @@
> >  #define X86_FEATURE_FSRC		(12*32+12) /* "" Fast short REP {CMPSB,SCASB} */
> >  #define X86_FEATURE_LKGS		(12*32+18) /* "" Load "kernel" (userspace) GS */
> >  #define X86_FEATURE_AMX_FP16		(12*32+21) /* "" AMX fp16 Support */
> > +#define X86_FEATURE_HRESET		(12*32+22) /* Hardware history reset instruction */
> 
>   #define X86_FEATURE_HRESET		(12*32+22) /* "" Hardware history reset instruction */
> 
> unless this really needs to be visible in /proc/cpuinfo:
> 
> Documentation/arch/x86/cpuinfo.rst

Good point. There is no need to expose HRESET in /proc/cpuinfo. I will
implement this change.