Commit 6bfa6d85 authored by Isaku Yamahata's avatar Isaku Yamahata Committed by Paolo Bonzini
Browse files

KVM: TDX: restore host xsave state when exit from the guest TD 



On exiting from the guest TD, xsave state is clobbered; restore it.
Do not use kvm_load_host_xsave_state(), as it relies on vcpu->arch
to find out whether other KVM_RUN code has loaded guest state into
XCR0/PKRU/XSS or not.  In the case of TDX, the exit values are known
independent of the guest CR0 and CR4, and in fact the latter are not
available.

Signed-off-by: default avatarIsaku Yamahata <isaku.yamahata@intel.com>
Signed-off-by: default avatarAdrian Hunter <adrian.hunter@intel.com>
Message-ID: <20250129095902.16391-8-adrian.hunter@intel.com>
[Rewrite to not use kvm_load_host_xsave_state. - Paolo]
Reviewed-by: default avatarXiayao Li <xiaoyao.li@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 81bf40d5

arch/x86/kvm/vmx/tdx.c

+32 −0
Original line number Diff line number Diff line
@@ -2,6 +2,7 @@ 
#include <linux/cleanup.h>

#include <linux/cpu.h>

#include <asm/cpufeature.h>

#include <asm/fpu/xcr.h>

#include <linux/misc_cgroup.h>

#include <linux/mmu_context.h>

#include <asm/tdx.h>
@@ -740,6 +741,30 @@ static noinstr void tdx_vcpu_enter_exit(struct kvm_vcpu *vcpu) 
				 BIT_ULL(VCPU_REGS_R14) | \

				 BIT_ULL(VCPU_REGS_R15))



static void tdx_load_host_xsave_state(struct kvm_vcpu *vcpu)

{

	struct kvm_tdx *kvm_tdx = to_kvm_tdx(vcpu->kvm);



	/*

	 * All TDX hosts support PKRU; but even if they didn't,

	 * vcpu->arch.host_pkru would be 0 and the wrpkru would be

	 * skipped.

	 */

	if (vcpu->arch.host_pkru != 0)

		wrpkru(vcpu->arch.host_pkru);



	if (kvm_host.xcr0 != (kvm_tdx->xfam & kvm_caps.supported_xcr0))

		xsetbv(XCR_XFEATURE_ENABLED_MASK, kvm_host.xcr0);



	/*

	 * Likewise, even if a TDX hosts didn't support XSS both arms of

	 * the comparison would be 0 and the wrmsrl would be skipped.

	 */

	if (kvm_host.xss != (kvm_tdx->xfam & kvm_caps.supported_xss))

		wrmsrl(MSR_IA32_XSS, kvm_host.xss);

}

EXPORT_SYMBOL_GPL(kvm_load_host_xsave_state);



fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit)

{

	/*
@@ -756,6 +781,8 @@ fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit) 


	tdx_vcpu_enter_exit(vcpu);



	tdx_load_host_xsave_state(vcpu);



	vcpu->arch.regs_avail &= TDX_REGS_AVAIL_SET;



	trace_kvm_exit(vcpu, KVM_ISA_VMX);
@@ -2332,6 +2359,11 @@ int __init tdx_bringup(void) 
		goto success_disable_tdx;

	}



	if (!cpu_feature_enabled(X86_FEATURE_OSXSAVE)) {

		pr_err("tdx: OSXSAVE is required for TDX\n");

		goto success_disable_tdx;

	}



	if (!cpu_feature_enabled(X86_FEATURE_MOVDIR64B)) {

		pr_err("tdx: MOVDIR64B is required for TDX\n");

		goto success_disable_tdx;