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    Subject[RFC PATCH v5 066/104] KVM: TDX: restore host xsave state when exit from the guest TD
    Date
    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 7a288aae03ba..54be5be1a06c 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"
    @@ -549,6 +550,22 @@ 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 & 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 & (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,
    @@ -572,6 +589,7 @@ 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
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