Re: [PATCH v6 43/60] i386/tdx: Only configure MSR_IA32_UCODE_REV in kvm_init_msrs() for TDs

Ira Weiny
2024-12-13T14:42:42Z

On Tue, Nov 05, 2024 at 01:23:51AM -0500, Xiaoyao Li wrote:
> For TDs, only MSR_IA32_UCODE_REV in kvm_init_msrs() can be configured
> by VMM, while the features enumerated/controlled by other MSRs except
> MSR_IA32_UCODE_REV in kvm_init_msrs() are not under control of VMM.

I'm confused by this commit message. If these features are not under VMM
control with TDX who controls them? I assume it is the TDX module. But where
are the qemu hooks to talk to the module? Are they not needed in qemu at all?

Also, why are the has_msr_* flags true for a TDX TD in the first place?

Ira

>
> Only configure MSR_IA32_UCODE_REV for TDs.
>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> Acked-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
> target/i386/kvm/kvm.c | 44 ++++++++++++++++++++++---------------------
> 1 file changed, 23 insertions(+), 21 deletions(-)
>
> diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
> index 595439f4a4d6..8909fce14909 100644
> --- a/target/i386/kvm/kvm.c
> +++ b/target/i386/kvm/kvm.c
> @@ -3852,32 +3852,34 @@ static void kvm_init_msrs(X86CPU *cpu)
> CPUX86State *env = &cpu->env;
>
> kvm_msr_buf_reset(cpu);
> - if (has_msr_arch_capabs) {
> - kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
> - env->features[FEAT_ARCH_CAPABILITIES]);
> - }
> -
> - if (has_msr_core_capabs) {
> - kvm_msr_entry_add(cpu, MSR_IA32_CORE_CAPABILITY,
> - env->features[FEAT_CORE_CAPABILITY]);
> - }
> -
> - if (has_msr_perf_capabs && cpu->enable_pmu) {
> - kvm_msr_entry_add_perf(cpu, env->features);
> +
> + if (!is_tdx_vm()) {
> + if (has_msr_arch_capabs) {
> + kvm_msr_entry_add(cpu, MSR_IA32_ARCH_CAPABILITIES,
> + env->features[FEAT_ARCH_CAPABILITIES]);
> + }
> +
> + if (has_msr_core_capabs) {
> + kvm_msr_entry_add(cpu, MSR_IA32_CORE_CAPABILITY,
> + env->features[FEAT_CORE_CAPABILITY]);
> + }
> +
> + if (has_msr_perf_capabs && cpu->enable_pmu) {
> + kvm_msr_entry_add_perf(cpu, env->features);
> + }
> +
> + /*
> + * Older kernels do not include VMX MSRs in KVM_GET_MSR_INDEX_LIST, but
> + * all kernels with MSR features should have them.
> + */
> + if (kvm_feature_msrs && cpu_has_vmx(env)) {
> + kvm_msr_entry_add_vmx(cpu, env->features);
> + }
> }
>
> if (has_msr_ucode_rev) {
> kvm_msr_entry_add(cpu, MSR_IA32_UCODE_REV, cpu->ucode_rev);
> }
> -
> - /*
> - * Older kernels do not include VMX MSRs in KVM_GET_MSR_INDEX_LIST, but
> - * all kernels with MSR features should have them.
> - */
> - if (kvm_feature_msrs && cpu_has_vmx(env)) {
> - kvm_msr_entry_add_vmx(cpu, env->features);
> - }
> -
> assert(kvm_buf_set_msrs(cpu) == 0);
> }
>
> --
> 2.34.1
>