Re: [PATCH v3 17/20] i386/cpu: Advertise CET related flags in feature words

[Xiaoyao Li <xiaoyao.li@intel.com>]

On 10/24/2025 2:56 PM, Zhao Liu wrote:
> From: Yang Weijiang <weijiang.yang@intel.com>
> 
> Add SHSTK and IBT flags in feature words with entry/exit
> control flags.
> 
> CET SHSTK and IBT feature are enumerated via CPUID(EAX=7,ECX=0)
> ECX[bit 7] and EDX[bit 20]. CET states load/restore at vmentry/
> vmexit are controlled by VMX_ENTRY_CTLS[bit 20] and VMX_EXIT_CTLS[bit 28].
> Enable these flags so that KVM can enumerate the features properly.
> 
> Tested-by: Farrah Chen <farrah.chen@intel.com>
> Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
> Co-developed-by: Chao Gao <chao.gao@intel.com>
> Signed-off-by: Chao Gao <chao.gao@intel.com>
> Co-developed-by: Zhao Liu <zhao1.liu@intel.com>
> Signed-off-by: Zhao Liu <zhao1.liu@intel.com>

Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>

> ---
> Changes Since v2:
>   - Rename "shstk"/"ibt" to "cet-ss"/"cet-ibt" to match feature names
>     in SDM & APM.
>   - Rename "vmx-exit-save-cet-ctl"/"vmx-entry-load-cet-ctl" to
>     "vmx-exit-save-cet"/"vmx-entry-load-cet".
>   - Define the feature mask macro for easier double check.
> ---
>   target/i386/cpu.c | 8 ++++----
>   target/i386/cpu.h | 2 ++
>   2 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index c08066a338a3..9a1001c47891 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -1221,7 +1221,7 @@ FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
>           .type = CPUID_FEATURE_WORD,
>           .feat_names = {
>               NULL, "avx512vbmi", "umip", "pku",
> -            NULL /* ospke */, "waitpkg", "avx512vbmi2", NULL,
> +            NULL /* ospke */, "waitpkg", "avx512vbmi2", "cet-ss",
>               "gfni", "vaes", "vpclmulqdq", "avx512vnni",
>               "avx512bitalg", NULL, "avx512-vpopcntdq", NULL,
>               "la57", NULL, NULL, NULL,
> @@ -1244,7 +1244,7 @@ FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
>               "avx512-vp2intersect", NULL, "md-clear", NULL,
>               NULL, NULL, "serialize", NULL,
>               "tsx-ldtrk", NULL, NULL /* pconfig */, "arch-lbr",
> -            NULL, NULL, "amx-bf16", "avx512-fp16",
> +            "cet-ibt", NULL, "amx-bf16", "avx512-fp16",
>               "amx-tile", "amx-int8", "spec-ctrl", "stibp",
>               "flush-l1d", "arch-capabilities", "core-capability", "ssbd",
>           },
> @@ -1666,7 +1666,7 @@ FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
>               "vmx-exit-save-efer", "vmx-exit-load-efer",
>                   "vmx-exit-save-preemption-timer", "vmx-exit-clear-bndcfgs",
>               NULL, "vmx-exit-clear-rtit-ctl", NULL, NULL,
> -            NULL, "vmx-exit-load-pkrs", NULL, "vmx-exit-secondary-ctls",
> +            "vmx-exit-save-cet", "vmx-exit-load-pkrs", NULL, "vmx-exit-secondary-ctls",
>           },
>           .msr = {
>               .index = MSR_IA32_VMX_TRUE_EXIT_CTLS,
> @@ -1681,7 +1681,7 @@ FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
>               NULL, "vmx-entry-ia32e-mode", NULL, NULL,
>               NULL, "vmx-entry-load-perf-global-ctrl", "vmx-entry-load-pat", "vmx-entry-load-efer",
>               "vmx-entry-load-bndcfgs", NULL, "vmx-entry-load-rtit-ctl", NULL,
> -            NULL, NULL, "vmx-entry-load-pkrs", "vmx-entry-load-fred",
> +            "vmx-entry-load-cet", NULL, "vmx-entry-load-pkrs", "vmx-entry-load-fred",
>               NULL, NULL, NULL, NULL,
>               NULL, NULL, NULL, NULL,
>           },
> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> index ad4287822831..fa3e5d87fe50 100644
> --- a/target/i386/cpu.h
> +++ b/target/i386/cpu.h
> @@ -1369,6 +1369,7 @@ uint64_t x86_cpu_get_supported_feature_word(X86CPU *cpu, FeatureWord w);
>   #define VMX_VM_EXIT_CLEAR_BNDCFGS                   0x00800000
>   #define VMX_VM_EXIT_PT_CONCEAL_PIP                  0x01000000
>   #define VMX_VM_EXIT_CLEAR_IA32_RTIT_CTL             0x02000000
> +#define VMX_VM_EXIT_SAVE_CET                        0x10000000
>   #define VMX_VM_EXIT_LOAD_IA32_PKRS                  0x20000000
>   #define VMX_VM_EXIT_ACTIVATE_SECONDARY_CONTROLS     0x80000000
>   
> @@ -1382,6 +1383,7 @@ uint64_t x86_cpu_get_supported_feature_word(X86CPU *cpu, FeatureWord w);
>   #define VMX_VM_ENTRY_LOAD_BNDCFGS                   0x00010000
>   #define VMX_VM_ENTRY_PT_CONCEAL_PIP                 0x00020000
>   #define VMX_VM_ENTRY_LOAD_IA32_RTIT_CTL             0x00040000
> +#define VMX_VM_ENTRY_LOAD_CET                       0x00100000
>   #define VMX_VM_ENTRY_LOAD_IA32_PKRS                 0x00400000
>   
>   /* Supported Hyper-V Enlightenments */