On 27/11/24 16:00, Sean Christopherson wrote:
> On Fri, Nov 22, 2024, Chao Gao wrote:
>>> +static bool tdparams_tsx_supported(struct kvm_cpuid2 *cpuid)
>>> +{
>>> + const struct kvm_cpuid_entry2 *entry;
>>> + u64 mask;
>>> + u32 ebx;
>>> +
>>> + entry = kvm_find_cpuid_entry2(cpuid->entries, cpuid->nent, 0x7, 0);
>>> + if (entry)
>>> + ebx = entry->ebx;
>>> + else
>>> + ebx = 0;
>>> +
>>> + mask = __feature_bit(X86_FEATURE_HLE) | __feature_bit(X86_FEATURE_RTM);
>>> + return ebx & mask;
>>> +}
>>> +
>>> static int setup_tdparams(struct kvm *kvm, struct td_params *td_params,
>>> struct kvm_tdx_init_vm *init_vm)
>>> {
>>> @@ -1299,6 +1322,7 @@ static int setup_tdparams(struct kvm *kvm, struct td_params *td_params,
>>> MEMCPY_SAME_SIZE(td_params->mrowner, init_vm->mrowner);
>>> MEMCPY_SAME_SIZE(td_params->mrownerconfig, init_vm->mrownerconfig);
>>>
>>> + to_kvm_tdx(kvm)->tsx_supported = tdparams_tsx_supported(cpuid);
>>> return 0;
>>> }
>>>
>>> @@ -2272,6 +2296,11 @@ static int __init __tdx_bringup(void)
>>> return -EIO;
>>> }
>>> }
>>> + tdx_uret_tsx_ctrl_slot = kvm_find_user_return_msr(MSR_IA32_TSX_CTRL);
>>> + if (tdx_uret_tsx_ctrl_slot == -1 && boot_cpu_has(X86_FEATURE_MSR_TSX_CTRL)) {
>>> + pr_err("MSR_IA32_TSX_CTRL isn't included by kvm_find_user_return_msr\n");
>>> + return -EIO;
>>> + }
>>>
>>> /*
>>> * Enabling TDX requires enabling hardware virtualization first,
>>> diff --git a/arch/x86/kvm/vmx/tdx.h b/arch/x86/kvm/vmx/tdx.h
>>> index 48cf0a1abfcc..815ff6bdbc7e 100644
>>> --- a/arch/x86/kvm/vmx/tdx.h
>>> +++ b/arch/x86/kvm/vmx/tdx.h
>>> @@ -29,6 +29,14 @@ struct kvm_tdx {
>>> u8 nr_tdcs_pages;
>>> u8 nr_vcpu_tdcx_pages;
>>>
>>> + /*
>>> + * Used on each TD-exit, see tdx_user_return_msr_update_cache().
>>> + * TSX_CTRL value on TD exit
>>> + * - set 0 if guest TSX enabled
>>> + * - preserved if guest TSX disabled
>>> + */
>>> + bool tsx_supported;
>>
>> Is it possible to drop this boolean and tdparams_tsx_supported()? I think we
>> can use the guest_can_use() framework instead.
>
> Yeah, though that optimized handling will soon come for free[*], and I plan on
> landing that sooner than TDX, so don't fret too much over this.
>
> [*] https://lore.kernel.org/all/20240517173926.965351-1-seanjc@xxxxxxxxxx
guest_can_use() is per-vcpu whereas we are currently using the
CPUID from TD_PARAMS (as per spec) before there are any VCPU's.
It is a bit of a disconnect so let's keep tsx_supported for now.
