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    SubjectRe: [PATCH v19 083/130] KVM: TDX: Add TSX_CTRL msr into uret_msrs list
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    On 2/26/2024 4:26 PM, isaku.yamahata@intel.com wrote:
    > From: Yang Weijiang <weijiang.yang@intel.com>
    >
    > TDX module resets the TSX_CTRL MSR to 0 at TD exit if TSX is enabled for
    > TD. Or it preserves the TSX_CTRL MSR if TSX is disabled for TD. VMM can
    > rely on uret_msrs mechanism to defer the reload of host value until exiting
    > to user space.
    >
    > Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
    > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
    > ---
    > v19:
    > - fix the type of tdx_uret_tsx_ctrl_slot. unguent int => int.
    > ---
    > arch/x86/kvm/vmx/tdx.c | 33 +++++++++++++++++++++++++++++++--
    > arch/x86/kvm/vmx/tdx.h | 8 ++++++++
    > 2 files changed, 39 insertions(+), 2 deletions(-)
    >
    > diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
    > index 7e2b1e554246..83dcaf5b6fbd 100644
    > --- a/arch/x86/kvm/vmx/tdx.c
    > +++ b/arch/x86/kvm/vmx/tdx.c
    > @@ -547,14 +547,21 @@ static struct tdx_uret_msr tdx_uret_msrs[] = {
    > {.msr = MSR_LSTAR,},
    > {.msr = MSR_TSC_AUX,},
    > };
    > +static int tdx_uret_tsx_ctrl_slot;
    >
    > -static void tdx_user_return_update_cache(void)
    > +static void tdx_user_return_update_cache(struct kvm_vcpu *vcpu)
    > {
    > int i;
    >
    > for (i = 0; i < ARRAY_SIZE(tdx_uret_msrs); i++)
    > kvm_user_return_update_cache(tdx_uret_msrs[i].slot,
    > tdx_uret_msrs[i].defval);
    > + /*
    > + * TSX_CTRL is reset to 0 if guest TSX is supported. Otherwise
    > + * preserved.
    > + */
    > + if (to_kvm_tdx(vcpu->kvm)->tsx_supported && tdx_uret_tsx_ctrl_slot != -1)

    If to_kvm_tdx(vcpu->kvm)->tsx_supported is true, tdx_uret_tsx_ctrl_slot
    shouldn't be -1 at this point.
    Otherwise, it's a KVM bug, right?
    Not sure if it needs a warning if tdx_uret_tsx_ctrl_slot is -1, or just
    remove the check?

    > + kvm_user_return_update_cache(tdx_uret_tsx_ctrl_slot, 0);
    > }
    >
    > static void tdx_restore_host_xsave_state(struct kvm_vcpu *vcpu)
    > @@ -649,7 +656,7 @@ fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu)
    >
    > tdx_vcpu_enter_exit(tdx);
    >
    > - tdx_user_return_update_cache();
    > + tdx_user_return_update_cache(vcpu);
    > tdx_restore_host_xsave_state(vcpu);
    > tdx->host_state_need_restore = true;
    >
    > @@ -1167,6 +1174,22 @@ static int setup_tdparams_xfam(struct kvm_cpuid2 *cpuid, struct td_params *td_pa
    > return 0;
    > }
    >
    > +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)
    > {
    > @@ -1209,6 +1232,7 @@ 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;
    > }
    >
    > @@ -2014,6 +2038,11 @@ int __init tdx_hardware_setup(struct kvm_x86_ops *x86_ops)
    > 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;
    > + }
    >
    > max_pkgs = topology_max_packages();
    > tdx_mng_key_config_lock = kcalloc(max_pkgs, sizeof(*tdx_mng_key_config_lock),
    > diff --git a/arch/x86/kvm/vmx/tdx.h b/arch/x86/kvm/vmx/tdx.h
    > index e96c416e73bf..44eab734e702 100644
    > --- a/arch/x86/kvm/vmx/tdx.h
    > +++ b/arch/x86/kvm/vmx/tdx.h
    > @@ -17,6 +17,14 @@ struct kvm_tdx {
    > u64 xfam;
    > int hkid;
    >
    > + /*
    > + * Used on each TD-exit, see tdx_user_return_update_cache().
    > + * TSX_CTRL value on TD exit
    > + * - set 0 if guest TSX enabled
    > + * - preserved if guest TSX disabled
    > + */
    > + bool tsx_supported;
    > +
    > bool finalized;
    > atomic_t tdh_mem_track;
    >


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