From 1be0e61c1f255faaeab04a390e00c8b9b9042870 Mon Sep 17 00:00:00 2001 From: Xiao Guangrong Date: Tue, 22 Mar 2016 16:51:18 +0800 Subject: [PATCH] KVM, pkeys: save/restore PKRU when guest/host switches Currently XSAVE state of host is not restored after VM-exit and PKRU is managed by XSAVE so the PKRU from guest is still controlling the memory access even if the CPU is running the code of host. This is not safe as KVM needs to access the memory of userspace (e,g QEMU) to do some emulation. So we save/restore PKRU when guest/host switches. Signed-off-by: Huaitong Han Signed-off-by: Xiao Guangrong Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 1b8a41f..8766477 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -598,6 +598,10 @@ struct vcpu_vmx { struct page *pml_pg; u64 current_tsc_ratio; + + bool guest_pkru_valid; + u32 guest_pkru; + u32 host_pkru; }; enum segment_cache_field { @@ -2107,6 +2111,7 @@ static void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu) } while (cmpxchg(&pi_desc->control, old.control, new.control) != old.control); } + /* * Switches to specified vcpu, until a matching vcpu_put(), but assumes * vcpu mutex is already taken. @@ -2167,6 +2172,7 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu) } vmx_vcpu_pi_load(vcpu, cpu); + vmx->host_pkru = read_pkru(); } static void vmx_vcpu_pi_put(struct kvm_vcpu *vcpu) @@ -8639,6 +8645,9 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu) if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) vmx_set_interrupt_shadow(vcpu, 0); + if (vmx->guest_pkru_valid) + __write_pkru(vmx->guest_pkru); + atomic_switch_perf_msrs(vmx); debugctlmsr = get_debugctlmsr(); @@ -8779,6 +8788,20 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu) vmx->exit_reason = vmcs_read32(VM_EXIT_REASON); /* + * eager fpu is enabled if PKEY is supported and CR4 is switched + * back on host, so it is safe to read guest PKRU from current + * XSAVE. + */ + if (boot_cpu_has(X86_FEATURE_OSPKE)) { + vmx->guest_pkru = __read_pkru(); + if (vmx->guest_pkru != vmx->host_pkru) { + vmx->guest_pkru_valid = true; + __write_pkru(vmx->host_pkru); + } else + vmx->guest_pkru_valid = false; + } + + /* * the KVM_REQ_EVENT optimization bit is only on for one entry, and if * we did not inject a still-pending event to L1 now because of * nested_run_pending, we need to re-enable this bit. -- 2.7.4