Add the CPUID bit indicates that a WRMSR to MSR_FS_BASE, MSR_GS_BASE, or
MSR_KERNEL_GS_BASE is non-serializing.

CPUID_Fn80000021_EAX
Bit    Feature description
1      FsGsKernelGsBaseNonSerializing.
       WRMSR to FS_BASE, GS_BASE and KernelGSbase are non-serializing.

Link: https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/programmer-references/57238.zip
Signed-off-by: Babu Moger <babu.moger@amd.com>
Reviewed-by: Maksim Davydov <davydov-max@yandex-team.ru>
---
 target/i386/cpu.c | 2 +-
 target/i386/cpu.h | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 7d18557877..710b862eec 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -1234,7 +1234,7 @@ FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
     [FEAT_8000_0021_EAX] = {
         .type = CPUID_FEATURE_WORD,
         .feat_names = {
-            "no-nested-data-bp", NULL, "lfence-always-serializing", NULL,
+            "no-nested-data-bp", "fs-gs-base-ns", "lfence-always-serializing", NULL,
             NULL, NULL, "null-sel-clr-base", NULL,
             "auto-ibrs", NULL, NULL, NULL,
             NULL, NULL, NULL, NULL,
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index c67b42d34f..968b4fd99b 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -1074,6 +1074,8 @@ uint64_t x86_cpu_get_supported_feature_word(X86CPU *cpu, FeatureWord w);
 
 /* Processor ignores nested data breakpoints */
 #define CPUID_8000_0021_EAX_NO_NESTED_DATA_BP            (1U << 0)
+/* WRMSR to FS_BASE, GS_BASE, or KERNEL_GS_BASE is non-serializing */
+#define CPUID_8000_0021_EAX_FS_GS_BASE_NS                (1U << 1)
 /* LFENCE is always serializing */
 #define CPUID_8000_0021_EAX_LFENCE_ALWAYS_SERIALIZING    (1U << 2)
 /* Null Selector Clears Base */
-- 
2.34.1

On Thu, Feb 06, 2025 at 01:28:37PM -0600, Babu Moger wrote:
> Date: Thu, 6 Feb 2025 13:28:37 -0600
> From: Babu Moger <babu.moger@amd.com>
> Subject: [PATCH v5 4/6] target/i386: Add feature that indicates WRMSR to
>  BASE reg is non-serializing
> X-Mailer: git-send-email 2.34.1
> 
> Add the CPUID bit indicates that a WRMSR to MSR_FS_BASE, MSR_GS_BASE, or
> MSR_KERNEL_GS_BASE is non-serializing.
> 
> CPUID_Fn80000021_EAX
> Bit    Feature description
> 1      FsGsKernelGsBaseNonSerializing.
>        WRMSR to FS_BASE, GS_BASE and KernelGSbase are non-serializing.
> 
> Link: https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/programmer-references/57238.zip
> Signed-off-by: Babu Moger <babu.moger@amd.com>
> Reviewed-by: Maksim Davydov <davydov-max@yandex-team.ru>
> ---
>  target/i386/cpu.c | 2 +-
>  target/i386/cpu.h | 2 ++
>  2 files changed, 3 insertions(+), 1 deletion(-)

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>

Hi Zhao,

On 2/20/2025 6:00 AM, Zhao Liu wrote:
> On Thu, Feb 06, 2025 at 01:28:37PM -0600, Babu Moger wrote:
>> Date: Thu, 6 Feb 2025 13:28:37 -0600
>> From: Babu Moger <babu.moger@amd.com>
>> Subject: [PATCH v5 4/6] target/i386: Add feature that indicates WRMSR to
>>   BASE reg is non-serializing
>> X-Mailer: git-send-email 2.34.1
>>
>> Add the CPUID bit indicates that a WRMSR to MSR_FS_BASE, MSR_GS_BASE, or
>> MSR_KERNEL_GS_BASE is non-serializing.
>>
>> CPUID_Fn80000021_EAX
>> Bit    Feature description
>> 1      FsGsKernelGsBaseNonSerializing.
>>         WRMSR to FS_BASE, GS_BASE and KernelGSbase are non-serializing.
>>
>> Link: https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/programmer-references/57238.zip
>> Signed-off-by: Babu Moger <babu.moger@amd.com>
>> Reviewed-by: Maksim Davydov <davydov-max@yandex-team.ru>
>> ---
>>   target/i386/cpu.c | 2 +-
>>   target/i386/cpu.h | 2 ++
>>   2 files changed, 3 insertions(+), 1 deletion(-)
> 
> Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
> 

Thank you,
Babu