| Date | Fri, 15 Apr 2022 15:56:59 +0200 | Subject | Re: [RFC PATCH v5 065/104] KVM: TDX: vcpu_run: save/restore host state(host kernel gs) | From | Paolo Bonzini <> |
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On 3/4/22 20:49, isaku.yamahata@intel.com wrote: > From: Isaku Yamahata <isaku.yamahata@intel.com> > > On entering/exiting TDX vcpu, Preserved or clobbered CPU state is different > from VMX case. Add TDX hooks to save/restore host/guest CPU state. > Save/restore kernel GS base MSR. > > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com> > --- > arch/x86/kvm/vmx/main.c | 28 +++++++++++++++++++++++++-- > arch/x86/kvm/vmx/tdx.c | 39 ++++++++++++++++++++++++++++++++++++++ > arch/x86/kvm/vmx/tdx.h | 4 ++++ > arch/x86/kvm/vmx/x86_ops.h | 4 ++++ > 4 files changed, 73 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c > index 2e5a7a72d560..f9d43f2de145 100644 > --- a/arch/x86/kvm/vmx/main.c > +++ b/arch/x86/kvm/vmx/main.c > @@ -89,6 +89,30 @@ static void vt_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) > return vmx_vcpu_reset(vcpu, init_event); > } > > +static void vt_prepare_switch_to_guest(struct kvm_vcpu *vcpu) > +{ > + /* > + * All host state is saved/restored across SEAMCALL/SEAMRET, and the > + * guest state of a TD is obviously off limits. Deferring MSRs and DRs > + * is pointless because the TDX module needs to load *something* so as > + * not to expose guest state. > + */ > + if (is_td_vcpu(vcpu)) { > + tdx_prepare_switch_to_guest(vcpu); > + return; > + } > + > + vmx_prepare_switch_to_guest(vcpu); > +} > + > +static void vt_vcpu_put(struct kvm_vcpu *vcpu) > +{ > + if (is_td_vcpu(vcpu)) > + return tdx_vcpu_put(vcpu); > + > + return vmx_vcpu_put(vcpu); > +} > + > static fastpath_t vt_vcpu_run(struct kvm_vcpu *vcpu) > { > if (is_td_vcpu(vcpu)) > @@ -174,9 +198,9 @@ struct kvm_x86_ops vt_x86_ops __initdata = { > .vcpu_free = vt_vcpu_free, > .vcpu_reset = vt_vcpu_reset, > > - .prepare_guest_switch = vmx_prepare_switch_to_guest, > + .prepare_guest_switch = vt_prepare_switch_to_guest, > .vcpu_load = vmx_vcpu_load, > - .vcpu_put = vmx_vcpu_put, > + .vcpu_put = vt_vcpu_put, > > .update_exception_bitmap = vmx_update_exception_bitmap, > .get_msr_feature = vmx_get_msr_feature, > diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c > index ebe4f9bf19e7..7a288aae03ba 100644 > --- a/arch/x86/kvm/vmx/tdx.c > +++ b/arch/x86/kvm/vmx/tdx.c > @@ -1,5 +1,6 @@ > // SPDX-License-Identifier: GPL-2.0 > #include <linux/cpu.h> > +#include <linux/mmu_context.h> > > #include <asm/tdx.h> > > @@ -407,6 +408,9 @@ int tdx_vcpu_create(struct kvm_vcpu *vcpu) > vcpu->arch.guest_state_protected = > !(to_kvm_tdx(vcpu->kvm)->attributes & TDX_TD_ATTRIBUTE_DEBUG); > > + tdx->host_state_need_save = true; > + tdx->host_state_need_restore = false; > + > return 0; > > free_tdvpx: > @@ -420,6 +424,39 @@ int tdx_vcpu_create(struct kvm_vcpu *vcpu) > return ret; > } > > +void tdx_prepare_switch_to_guest(struct kvm_vcpu *vcpu) > +{ > + struct vcpu_tdx *tdx = to_tdx(vcpu); > + > + if (!tdx->host_state_need_save) > + return; > + > + if (likely(is_64bit_mm(current->mm))) > + tdx->msr_host_kernel_gs_base = current->thread.gsbase; > + else > + tdx->msr_host_kernel_gs_base = read_msr(MSR_KERNEL_GS_BASE); > + > + tdx->host_state_need_save = false; > +} > + > +static void tdx_prepare_switch_to_host(struct kvm_vcpu *vcpu) > +{ > + struct vcpu_tdx *tdx = to_tdx(vcpu); > + > + tdx->host_state_need_save = true; > + if (!tdx->host_state_need_restore) > + return; > + > + wrmsrl(MSR_KERNEL_GS_BASE, tdx->msr_host_kernel_gs_base); > + tdx->host_state_need_restore = false; > +} > + > +void tdx_vcpu_put(struct kvm_vcpu *vcpu) > +{ > + vmx_vcpu_pi_put(vcpu); > + tdx_prepare_switch_to_host(vcpu); > +} > + > void tdx_vcpu_free(struct kvm_vcpu *vcpu) > { > struct vcpu_tdx *tdx = to_tdx(vcpu); > @@ -535,6 +572,8 @@ fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu) > > tdx_vcpu_enter_exit(vcpu, tdx); > > + tdx->host_state_need_restore = true; > + > vcpu->arch.regs_avail &= ~VMX_REGS_LAZY_LOAD_SET; > trace_kvm_exit(vcpu, KVM_ISA_VMX); > > diff --git a/arch/x86/kvm/vmx/tdx.h b/arch/x86/kvm/vmx/tdx.h > index e950404ce5de..8b1cf9c158e3 100644 > --- a/arch/x86/kvm/vmx/tdx.h > +++ b/arch/x86/kvm/vmx/tdx.h > @@ -84,6 +84,10 @@ struct vcpu_tdx { > union tdx_exit_reason exit_reason; > > bool initialized; > + > + bool host_state_need_save; > + bool host_state_need_restore; > + u64 msr_host_kernel_gs_base; > }; > > static inline bool is_td(struct kvm *kvm) > diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h > index 44404dd25737..8b871c5f52cf 100644 > --- a/arch/x86/kvm/vmx/x86_ops.h > +++ b/arch/x86/kvm/vmx/x86_ops.h > @@ -141,6 +141,8 @@ int tdx_vcpu_create(struct kvm_vcpu *vcpu); > void tdx_vcpu_free(struct kvm_vcpu *vcpu); > void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event); > fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu); > +void tdx_prepare_switch_to_guest(struct kvm_vcpu *vcpu); > +void tdx_vcpu_put(struct kvm_vcpu *vcpu); > > int tdx_vm_ioctl(struct kvm *kvm, void __user *argp); > int tdx_vcpu_ioctl(struct kvm_vcpu *vcpu, void __user *argp); > @@ -162,6 +164,8 @@ static inline int tdx_vcpu_create(struct kvm_vcpu *vcpu) { return -EOPNOTSUPP; } > static inline void tdx_vcpu_free(struct kvm_vcpu *vcpu) {} > static inline void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) {} > static inline fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu) { return EXIT_FASTPATH_NONE; } > +static inline void tdx_prepare_switch_to_guest(struct kvm_vcpu *vcpu) {} > +static inline void tdx_vcpu_put(struct kvm_vcpu *vcpu) {} > > static inline int tdx_vm_ioctl(struct kvm *kvm, void __user *argp) { return -EOPNOTSUPP; } > static inline int tdx_vcpu_ioctl(struct kvm_vcpu *vcpu, void __user *argp) { return -EOPNOTSUPP; }
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
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