linux-kernel - Re: [PATCH v14 02/13] x86/mm: get INVLPGB count max from CPUID

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Message-ID: <20250228192747.GFZ8IOM2WkIx1lbCt1@fat_crate.local>
Date: Fri, 28 Feb 2025 20:27:47 +0100
From: Borislav Petkov <bp@...en8.de>
To: Rik van Riel <riel@...riel.com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, peterz@...radead.org,
	dave.hansen@...ux.intel.com, zhengqi.arch@...edance.com,
	nadav.amit@...il.com, thomas.lendacky@....com, kernel-team@...a.com,
	linux-mm@...ck.org, akpm@...ux-foundation.org, jackmanb@...gle.com,
	jannh@...gle.com, mhklinux@...look.com, andrew.cooper3@...rix.com,
	Manali.Shukla@....com, mingo@...nel.org,
	Dave Hansen <dave.hansen@...el.com>
Subject: Re: [PATCH v14 02/13] x86/mm: get INVLPGB count max from CPUID

On Tue, Feb 25, 2025 at 10:00:37PM -0500, Rik van Riel wrote:
> The CPU advertises the maximum number of pages that can be shot down
> with one INVLPGB instruction in the CPUID data.
> 
> Save that information for later use.
> 
> Signed-off-by: Rik van Riel <riel@...riel.com>
> Tested-by: Manali Shukla <Manali.Shukla@....com>
> Tested-by: Brendan Jackman <jackmanb@...gle.com>
> Tested-by: Michael Kelley <mhklinux@...look.com>
> Acked-by: Dave Hansen <dave.hansen@...el.com>
> ---
>  arch/x86/Kconfig.cpu               | 4 ++++
>  arch/x86/include/asm/cpufeatures.h | 1 +
>  arch/x86/include/asm/tlbflush.h    | 3 +++
>  arch/x86/kernel/cpu/amd.c          | 6 ++++++
>  4 files changed, 14 insertions(+)

As discussed, changed ontop.

 diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu
-index 2a7279d80460..981def9cbfac 100644
+index f8b3296fe2e1..63864f5348f2 100644
 --- a/arch/x86/Kconfig.cpu
 +++ b/arch/x86/Kconfig.cpu
-@@ -401,6 +401,10 @@ menuconfig PROCESSOR_SELECT
+@@ -334,6 +334,10 @@ menuconfig PROCESSOR_SELECT
  	  This lets you choose what x86 vendor support code your kernel
  	  will include.
  
@@ -37,14 +36,14 @@ index 2a7279d80460..981def9cbfac 100644
  	default y
  	bool "Support Intel processors" if PROCESSOR_SELECT
 diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
-index 508c0dad116b..b5c66b7465ba 100644
+index d5985e8eef29..c0462be0c5f6 100644
 --- a/arch/x86/include/asm/cpufeatures.h
 +++ b/arch/x86/include/asm/cpufeatures.h
-@@ -338,6 +338,7 @@
+@@ -330,6 +330,7 @@
  #define X86_FEATURE_CLZERO		(13*32+ 0) /* "clzero" CLZERO instruction */
  #define X86_FEATURE_IRPERF		(13*32+ 1) /* "irperf" Instructions Retired Count */
  #define X86_FEATURE_XSAVEERPTR		(13*32+ 2) /* "xsaveerptr" Always save/restore FP error pointers */
-+#define X86_FEATURE_INVLPGB		(13*32+ 3) /* INVLPGB and TLBSYNC instruction supported. */
++#define X86_FEATURE_INVLPGB		(13*32+ 3) /* INVLPGB and TLBSYNC instructions supported */
  #define X86_FEATURE_RDPRU		(13*32+ 4) /* "rdpru" Read processor register at user level */
  #define X86_FEATURE_WBNOINVD		(13*32+ 9) /* "wbnoinvd" WBNOINVD instruction */
  #define X86_FEATURE_AMD_IBPB		(13*32+12) /* Indirect Branch Prediction Barrier */
@@ -63,7 +62,7 @@ index 3da645139748..855c13da2045 100644
  
  /*
 diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
-index 54194f5995de..3c75c174a274 100644
+index d747515ad013..0e2e9af18cef 100644
 --- a/arch/x86/kernel/cpu/amd.c
 +++ b/arch/x86/kernel/cpu/amd.c
 @@ -29,6 +29,8 @@
@@ -81,11 +80,11 @@ index 54194f5995de..3c75c174a274 100644
  	tlb_lli_4m[ENTRIES] = tlb_lli_2m[ENTRIES] >> 1;
 +
 +	/* Max number of pages INVLPGB can invalidate in one shot */
-+	if (boot_cpu_has(X86_FEATURE_INVLPGB))
++	if (cpu_has(c, X86_FEATURE_INVLPGB))
 +		invlpgb_count_max = (cpuid_edx(0x80000008) & 0xffff) + 1;
  }
  
  static const struct cpu_dev amd_cpu_dev = {
 -- 

-- 
Regards/Gruss,
    Boris.

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