[PATCH v7 066/102] KVM: TDX: restore host xsave state when exit from the guest TD

isaku.yamahata
2022-06-27T21:56:53Z

From: Isaku Yamahata <isaku.yamahata@intel.com>

On exiting from the guest TD, xsave state is clobbered. Restore xsave
state on TD exit.

Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
---
arch/x86/kvm/vmx/tdx.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)

diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index d9e0dd30c150..277525b6ca51 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -2,6 +2,7 @@
#include <linux/cpu.h>
#include <linux/mmu_context.h>

+#include <asm/fpu/xcr.h>
#include <asm/tdx.h>

#include "capabilities.h"
@@ -592,6 +593,22 @@ void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
vcpu->kvm->vm_bugged = true;
}

+static void tdx_restore_host_xsave_state(struct kvm_vcpu *vcpu)
+{
+ struct kvm_tdx *kvm_tdx = to_kvm_tdx(vcpu->kvm);
+
+ if (static_cpu_has(X86_FEATURE_XSAVE) &&
+ host_xcr0 != (kvm_tdx->xfam & kvm_caps.supported_xcr0))
+ xsetbv(XCR_XFEATURE_ENABLED_MASK, host_xcr0);
+ if (static_cpu_has(X86_FEATURE_XSAVES) &&
+ /* PT can be exposed to TD guest regardless of KVM's XSS support */
+ host_xss != (kvm_tdx->xfam & (kvm_caps.supported_xss | XFEATURE_MASK_PT)))
+ wrmsrl(MSR_IA32_XSS, host_xss);
+ if (static_cpu_has(X86_FEATURE_PKU) &&
+ (kvm_tdx->xfam & XFEATURE_MASK_PKRU))
+ write_pkru(vcpu->arch.host_pkru);
+}
+
u64 __tdx_vcpu_run(hpa_t tdvpr, void *regs, u32 regs_mask);

static noinstr void tdx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
@@ -615,6 +632,7 @@ fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu)

tdx_vcpu_enter_exit(vcpu, tdx);

+ tdx_restore_host_xsave_state(vcpu);
tdx->host_state_need_restore = true;

vcpu->arch.regs_avail &= ~VMX_REGS_LAZY_LOAD_SET;
--
2.25.1