On 2/10/25 03:22, Nikunj A Dadhania wrote:
> From: Ketan Chaturvedi <Ketan.Chaturvedi@xxxxxxx>
>
> Add support for Secure TSC, allowing userspace to configure the Secure TSC
> feature for SNP guests. Use the SNP specification's desired TSC frequency
> parameter during the SNP_LAUNCH_START command to set the mean TSC
> frequency in KHz for Secure TSC enabled guests. If the frequency is not
> specified by the VMM, default to tsc_khz.
>
> Signed-off-by: Ketan Chaturvedi <Ketan.Chaturvedi@xxxxxxx>
> Co-developed-by: Nikunj A Dadhania <nikunj@xxxxxxx>
> Signed-off-by: Nikunj A Dadhania <nikunj@xxxxxxx>
> ---
> arch/x86/include/uapi/asm/kvm.h | 3 ++-
> arch/x86/kvm/svm/sev.c | 20 ++++++++++++++++++++
> include/linux/psp-sev.h | 2 ++
> 3 files changed, 24 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
> index 9e75da97bce0..8e090cab9aa0 100644
> --- a/arch/x86/include/uapi/asm/kvm.h
> +++ b/arch/x86/include/uapi/asm/kvm.h
> @@ -836,7 +836,8 @@ struct kvm_sev_snp_launch_start {
> __u64 policy;
> __u8 gosvw[16];
> __u16 flags;
> - __u8 pad0[6];
> + __u32 desired_tsc_khz;
This will put the __u32 field misaligned in the struct. You should
probably move the now 2-byte pad0 field to before the desired_tsc_khz field.
> + __u8 pad0[2];
> __u64 pad1[4];
> };
>
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 0a1fd5c034e2..0edd473749f7 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -2228,6 +2228,20 @@ static int snp_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
>
> start.gctx_paddr = __psp_pa(sev->snp_context);
> start.policy = params.policy;
> +
> + if (snp_secure_tsc_enabled(kvm)) {
> + u32 user_tsc_khz = params.desired_tsc_khz;
> +
> + /* Use tsc_khz if the VMM has not provided the TSC frequency */
> + if (!user_tsc_khz)
> + user_tsc_khz = tsc_khz;
> +
> + start.desired_tsc_khz = user_tsc_khz;
> +
> + /* Set the arch default TSC for the VM*/
> + kvm->arch.default_tsc_khz = user_tsc_khz;
> + }
> +
> memcpy(start.gosvw, params.gosvw, sizeof(params.gosvw));
> rc = __sev_issue_cmd(argp->sev_fd, SEV_CMD_SNP_LAUNCH_START, &start, &argp->error);
> if (rc) {
> @@ -2949,6 +2963,9 @@ void __init sev_set_cpu_caps(void)
> if (sev_snp_enabled) {
> kvm_cpu_cap_set(X86_FEATURE_SEV_SNP);
> kvm_caps.supported_vm_types |= BIT(KVM_X86_SNP_VM);
> +
> + if (cpu_feature_enabled(X86_FEATURE_SNP_SECURE_TSC))
> + kvm_cpu_cap_set(X86_FEATURE_SNP_SECURE_TSC);
> }
> }
>
> @@ -3071,6 +3088,9 @@ void __init sev_hardware_setup(void)
> sev_supported_vmsa_features = 0;
> if (sev_es_debug_swap_enabled)
> sev_supported_vmsa_features |= SVM_SEV_FEAT_DEBUG_SWAP;
> +
> + if (sev_snp_enabled && cpu_feature_enabled(X86_FEATURE_SNP_SECURE_TSC))
> + sev_supported_vmsa_features |= SVM_SEV_FEAT_SECURE_TSC;
> }
>
> void sev_hardware_unsetup(void)
> diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
> index 903ddfea8585..613a8209bed2 100644
> --- a/include/linux/psp-sev.h
> +++ b/include/linux/psp-sev.h
> @@ -594,6 +594,7 @@ struct sev_data_snp_addr {
> * @imi_en: launch flow is launching an IMI (Incoming Migration Image) for the
> * purpose of guest-assisted migration.
> * @rsvd: reserved
> + * @desired_tsc_khz: hypervisor desired mean TSC freq in kHz of the guest
> * @gosvw: guest OS-visible workarounds, as defined by hypervisor
> */
> struct sev_data_snp_launch_start {
> @@ -603,6 +604,7 @@ struct sev_data_snp_launch_start {
> u32 ma_en:1; /* In */
> u32 imi_en:1; /* In */
> u32 rsvd:30;
> + u32 desired_tsc_khz; /* In */
Shouldn't there be a separate fix for this before this patch? The
desired_tsc_freq should have been here all along, so before this patch,
the gosvw field is off by 4 bytes with sev_data_snp_launch_start not
being large enough compared to what the firmware is accessing, right?
Thanks,
Tom
> u8 gosvw[16]; /* In */
> } __packed;
>
