Tom Lendacky <thomas.lendacky@xxxxxxx> writes:
> 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.
>
Sure, will update.
>> + __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?
Yes, this should have been part of SNP series, I will separate this
change in a new patch with Fixes + stable tag.
Thanks
Nikunj
