Re: [PATCH v10 072/108] KVM: TDX: restore user ret MSRs

Isaku Yamahata
2022-11-17T20:14:37Z

On Mon, Nov 14, 2022 at 03:49:32PM +0800,
Binbin Wu <binbin.wu@linux.intel.com> wrote:

>
> On 10/30/2022 2:23 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 and before returning to ring 3.
> >
> > 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 3ec465cbaeef..f35ccf2b502d 100644
> > --- a/arch/x86/kvm/vmx/tdx.c
> > +++ b/arch/x86/kvm/vmx/tdx.c
> > @@ -456,6 +456,28 @@ void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
> > vcpu->kvm->vm_bugged = true;
> > }
> > +struct tdx_uret_msr {
> > + u32 msr;
> > + unsigned int slot;
> > + u64 defval;
> > +};
> > +
> > +static struct tdx_uret_msr tdx_uret_msrs[] = {
> > + {.msr = MSR_SYSCALL_MASK,},
> > + {.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);
> > @@ -495,6 +517,7 @@ fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu)
> > tdx_vcpu_enter_exit(vcpu, tdx);
> > + tdx_user_return_update_cache();
> > tdx_restore_host_xsave_state(vcpu);
> > tdx->host_state_need_restore = true;
> > @@ -1558,6 +1581,26 @@ int __init tdx_hardware_setup(struct kvm_x86_ops *x86_ops)
> > return -ENODEV;
> > }
> > + 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().
> > + * Here is setting up cpu feature before running vcpu,
> > + * registered is alreays
>
> typo, already or always?

already. Thanks.
--
Isaku Yamahata <isaku.yamahata@gmail.com>