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    SubjectRe: [PATCH v19 082/130] KVM: TDX: restore user ret MSRs
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    On 2/26/2024 4:26 PM, isaku.yamahata@intel.com wrote:
    > From: Isaku Yamahata <isaku.yamahata@intel.com>
    >
    > Several user ret MSRs are clobbered on TD exit. Restore those values on
    > TD exit

    Here "Restore" is not accurate, since the previous patch just updates
    the cached value on TD exit.

    > and before returning to ring 3. Because TSX_CTRL requires special
    > treat, this patch doesn't address it.
    >
    > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
    > Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
    > ---
    > arch/x86/kvm/vmx/tdx.c | 43 ++++++++++++++++++++++++++++++++++++++++++
    > 1 file changed, 43 insertions(+)
    >
    > diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
    > index 199226c6cf55..7e2b1e554246 100644
    > --- a/arch/x86/kvm/vmx/tdx.c
    > +++ b/arch/x86/kvm/vmx/tdx.c
    > @@ -535,6 +535,28 @@ void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
    > */
    > }
    >
    > +struct tdx_uret_msr {
    > + u32 msr;
    > + unsigned int slot;
    > + u64 defval;
    > +};
    > +
    > +static struct tdx_uret_msr tdx_uret_msrs[] = {
    > + {.msr = MSR_SYSCALL_MASK, .defval = 0x20200 },
    > + {.msr = MSR_STAR,},
    > + {.msr = MSR_LSTAR,},
    > + {.msr = MSR_TSC_AUX,},
    > +};
    > +
    > +static void tdx_user_return_update_cache(void)
    > +{
    > + 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);
    > +}
    > +
    > static void tdx_restore_host_xsave_state(struct kvm_vcpu *vcpu)
    > {
    > struct kvm_tdx *kvm_tdx = to_kvm_tdx(vcpu->kvm);
    > @@ -627,6 +649,7 @@ fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu)
    >
    > tdx_vcpu_enter_exit(tdx);
    >
    > + tdx_user_return_update_cache();
    > tdx_restore_host_xsave_state(vcpu);
    > tdx->host_state_need_restore = true;
    >
    > @@ -1972,6 +1995,26 @@ int __init tdx_hardware_setup(struct kvm_x86_ops *x86_ops)
    > return -EINVAL;
    > }
    >
    > + for (i = 0; i < ARRAY_SIZE(tdx_uret_msrs); i++) {
    > + /*
    > + * Here it checks if MSRs (tdx_uret_msrs) can be saved/restored
    > + * before returning to user space.
    > + *
    > + * this_cpu_ptr(user_return_msrs)->registered isn't checked
    > + * because the registration is done at vcpu runtime by
    > + * kvm_set_user_return_msr().
    Should be tdx_user_return_update_cache(), if it's the final API name.

    > + * Here is setting up cpu feature before running vcpu,
    > + * registered is already false.
                                      ^
                               remove "already"?

    > + */
    > + tdx_uret_msrs[i].slot = kvm_find_user_return_msr(tdx_uret_msrs[i].msr);
    > + if (tdx_uret_msrs[i].slot == -1) {
    > + /* If any MSR isn't supported, it is a KVM bug */
    > + pr_err("MSR %x isn't included by kvm_find_user_return_msr\n",
    > + tdx_uret_msrs[i].msr);
    > + return -EIO;
    > + }
    > + }
    > +
    > max_pkgs = topology_max_packages();
    > tdx_mng_key_config_lock = kcalloc(max_pkgs, sizeof(*tdx_mng_key_config_lock),
    > GFP_KERNEL);


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