Re: [PATCH 1/2] KVM: x86: simplify handling of PKRU

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On 2017/8/24 5:26, Paolo Bonzini wrote:
Move it to struct kvm_arch_vcpu, replacing guest_pkru_valid with a
simple comparison against the host value of the register.

Thanks for refine the patches.:)


Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
  arch/x86/include/asm/kvm_host.h |  1 +
  arch/x86/kvm/kvm_cache_regs.h   |  5 -----
  arch/x86/kvm/mmu.h              |  2 +-
  arch/x86/kvm/svm.c              |  7 -------
  arch/x86/kvm/vmx.c              | 23 ++++++-----------------
  5 files changed, 8 insertions(+), 30 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 643308143bea..beb185361045 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -491,6 +491,7 @@ struct kvm_vcpu_arch {
  	unsigned long cr4;
  	unsigned long cr4_guest_owned_bits;
  	unsigned long cr8;
+	u32 pkru;
  	u32 hflags;
  	u64 efer;
  	u64 apic_base;
diff --git a/arch/x86/kvm/kvm_cache_regs.h b/arch/x86/kvm/kvm_cache_regs.h
index 762cdf2595f9..e1e89ee4af75 100644
--- a/arch/x86/kvm/kvm_cache_regs.h
+++ b/arch/x86/kvm/kvm_cache_regs.h
@@ -84,11 +84,6 @@ static inline u64 kvm_read_edx_eax(struct kvm_vcpu *vcpu)
  		| ((u64)(kvm_register_read(vcpu, VCPU_REGS_RDX) & -1u) << 32);
  }
-static inline u32 kvm_read_pkru(struct kvm_vcpu *vcpu)
-{
-	return kvm_x86_ops->get_pkru(vcpu);
-}
-
  static inline void enter_guest_mode(struct kvm_vcpu *vcpu)
  {
  	vcpu->arch.hflags |= HF_GUEST_MASK;
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 3ed6192d93b1..1b3095264fcf 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -168,7 +168,7 @@ static inline u8 permission_fault(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
  		* index of the protection domain, so pte_pkey * 2 is
  		* is the index of the first bit for the domain.
  		*/
-		pkru_bits = (kvm_read_pkru(vcpu) >> (pte_pkey * 2)) & 3;
+		pkru_bits = (vcpu->arch.pkru >> (pte_pkey * 2)) & 3;
/* clear present bit, replace PFEC.RSVD with ACC_USER_MASK. */
  		offset = (pfec & ~1) +
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 32c8d8f62985..f2355135164c 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1826,11 +1826,6 @@ static void svm_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags)
  	to_svm(vcpu)->vmcb->save.rflags = rflags;
  }
-static u32 svm_get_pkru(struct kvm_vcpu *vcpu)
-{
-	return 0;
-}
-
  static void svm_cache_reg(struct kvm_vcpu *vcpu, enum kvm_reg reg)
  {
  	switch (reg) {
@@ -5438,8 +5433,6 @@ static void svm_setup_mce(struct kvm_vcpu *vcpu)
  	.get_rflags = svm_get_rflags,
  	.set_rflags = svm_set_rflags,
- .get_pkru = svm_get_pkru,
-
  	.tlb_flush = svm_flush_tlb,
.run = svm_vcpu_run,
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index ddabed8425b3..c603f658c42a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -639,8 +639,6 @@ struct vcpu_vmx {
u64 current_tsc_ratio; - bool guest_pkru_valid;
-	u32 guest_pkru;
  	u32 host_pkru;
/*
@@ -2392,11 +2390,6 @@ static void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags)
  		to_vmx(vcpu)->emulation_required = emulation_required(vcpu);
  }
-static u32 vmx_get_pkru(struct kvm_vcpu *vcpu)
-{
-	return to_vmx(vcpu)->guest_pkru;
-}
-
  static u32 vmx_get_interrupt_shadow(struct kvm_vcpu *vcpu)
  {
  	u32 interruptibility = vmcs_read32(GUEST_INTERRUPTIBILITY_INFO);
@@ -9239,8 +9232,9 @@ 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);
+	if (static_cpu_has(X86_FEATURE_OSPKE) &&

We expose protection key to VM without check whether OSPKE is enabled or not. Why not check guest's cpuid here which also can avoid unnecessary access to pkru?

+	    vcpu->arch.pkru != vmx->host_pkru)
+		__write_pkru(vcpu->arch.pkru);
atomic_switch_perf_msrs(vmx);
  	debugctlmsr = get_debugctlmsr();
@@ -9388,13 +9382,10 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
  	 * 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;
+	if (static_cpu_has(X86_FEATURE_OSPKE)) {
+		vcpu->arch.pkru = __read_pkru();
+		if (vcpu->arch.pkru != vmx->host_pkru)
  			__write_pkru(vmx->host_pkru);
-		} else
-			vmx->guest_pkru_valid = false;
  	}
/*
@@ -11875,8 +11866,6 @@ static void vmx_setup_mce(struct kvm_vcpu *vcpu)
  	.get_rflags = vmx_get_rflags,
  	.set_rflags = vmx_set_rflags,
- .get_pkru = vmx_get_pkru,
-
  	.tlb_flush = vmx_flush_tlb,
.run = vmx_vcpu_run,



--
Yang
Alibaba Cloud Computing



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