linux-kernel - [PATCH v18 069/121] KVM: TDX: restore host xsave state when exit from the guest TD

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Date: Mon, 22 Jan 2024 15:53:45 -0800
From: isaku.yamahata@...el.com
To: kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: isaku.yamahata@...el.com,
	isaku.yamahata@...il.com,
	Paolo Bonzini <pbonzini@...hat.com>,
	erdemaktas@...gle.com,
	Sean Christopherson <seanjc@...gle.com>,
	Sagi Shahar <sagis@...gle.com>,
	Kai Huang <kai.huang@...el.com>,
	chen.bo@...el.com,
	hang.yuan@...el.com,
	tina.zhang@...el.com
Subject: [PATCH v18 069/121] KVM: TDX: restore host xsave state when exit from the guest TD

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

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

Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
---
v15 -> v16:
- Added CET flag mask
---
 arch/x86/kvm/vmx/tdx.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index 903f4abb3543..fe818cfde9e7 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"
@@ -584,6 +585,23 @@ void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 	 */
 }
 
+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 | TDX_TD_XFAM_CET)))
+		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);
+}
+
 static noinstr void tdx_vcpu_enter_exit(struct vcpu_tdx *tdx)
 {
 	struct tdx_module_args args;
@@ -659,6 +677,7 @@ fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu)
 
 	tdx_vcpu_enter_exit(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