[PATCH v9 04/12] x86/mm: get INVLPGB count max from CPUID

Rik van Riel
2025-02-06T04:44:17Z

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@surriel.com>
Tested-by: Manali Shukla <Manali.Shukla@amd.com>
---
arch/x86/Kconfig.cpu | 5 +++++
arch/x86/include/asm/cpufeatures.h | 1 +
arch/x86/include/asm/tlbflush.h | 7 +++++++
arch/x86/kernel/cpu/amd.c | 8 ++++++++
4 files changed, 21 insertions(+)

diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu
index 2a7279d80460..abe013a1b076 100644
--- a/arch/x86/Kconfig.cpu
+++ b/arch/x86/Kconfig.cpu
@@ -395,6 +395,10 @@ config X86_VMX_FEATURE_NAMES
def_bool y
depends on IA32_FEAT_CTL

+config X86_BROADCAST_TLB_FLUSH
+ def_bool y
+ depends on CPU_SUP_AMD && 64BIT
+
menuconfig PROCESSOR_SELECT
bool "Supported processor vendors" if EXPERT
help
@@ -431,6 +435,7 @@ config CPU_SUP_CYRIX_32
config CPU_SUP_AMD
default y
bool "Support AMD processors" if PROCESSOR_SELECT
+ select X86_BROADCAST_TLB_FLUSH
help
This enables detection, tunings and quirks for AMD processors

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 17b6590748c0..f9b832e971c5 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -338,6 +338,7 @@
#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_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 */
diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index 02fc2aa06e9e..8fe3b2dda507 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -183,6 +183,13 @@ static inline void cr4_init_shadow(void)
extern unsigned long mmu_cr4_features;
extern u32 *trampoline_cr4_features;

+/* How many pages can we invalidate with one INVLPGB. */
+#ifdef CONFIG_X86_BROADCAST_TLB_FLUSH
+extern u16 invlpgb_count_max;
+#else
+#define invlpgb_count_max 1
+#endif
+
extern void initialize_tlbstate_and_flush(void);

/*
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 79d2e17f6582..bcf73775b4f8 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -29,6 +29,8 @@

#include "cpu.h"

+u16 invlpgb_count_max __ro_after_init;
+
static inline int rdmsrl_amd_safe(unsigned msr, unsigned long long *p)
{
u32 gprs[8] = { 0 };
@@ -1135,6 +1137,12 @@ static void cpu_detect_tlb_amd(struct cpuinfo_x86 *c)
tlb_lli_2m[ENTRIES] = eax & mask;

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)) {
+ cpuid(0x80000008, &eax, &ebx, &ecx, &edx);
+ invlpgb_count_max = (edx & 0xffff) + 1;
+ }
}

static const struct cpu_dev amd_cpu_dev = {
--
2.47.1