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Patch "KVM: x86: simplify handling of PKRU" has been added to the 4.12-stable tree

PATCH [email protected] 1 participant 1 message Aug 27, 2017

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This is a note to let you know that I've just added the patch titled

KVM: x86: simplify handling of PKRU

to the 4.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kvm-x86-simplify-handling-of-pkru.patch
and it can be found in the queue-4.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From b9dd21e104bcd45e124acfe978a79df71259e59b Mon Sep 17 00:00:00 2001

From: Paolo Bonzini <[email protected]>
Date: Wed, 23 Aug 2017 23:14:38 +0200
Subject: KVM: x86: simplify handling of PKRU

From: Paolo Bonzini <[email protected]>

commit b9dd21e104bcd45e124acfe978a79df71259e59b upstream.

Move it to struct kvm_arch_vcpu, replacing guest_pkru_valid with a simple comparison against the host value of the register. The write of PKRU in addition can be skipped if the guest has not enabled the feature. Once we do this, we need not test OSPKE in the host anymore, because guest_CR4.PKE=1 implies host_CR4.PKE=1.

The static PKU test is kept to elide the code on older CPUs.

Suggested-by Yang Zhang <[email protected]>
Fixes 1be0e61c1f255faaeab04a390e00c8b9b9042870
Reviewed-by David Hildenbrand <[email protected]>
Signed-off-by Paolo Bonzini <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 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              |   25 ++++++++-----------------
 5 files changed, 10 insertions(+), 30 deletions(-)
arch/x86/include/asm/kvm_host.h +1 -0
@@ -486,6 +486,7 @@ 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;
arch/x86/kvm/kvm_cache_regs.h +0 -5
@@ -84,11 +84,6 @@ static inline u64 kvm_read_edx_eax(struc
 		| ((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;
arch/x86/kvm/mmu.h +1 -1
@@ -182,7 +182,7 @@ static inline u8 permission_fault(struct
 		* 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) +
arch/x86/kvm/svm.c +0 -7
@@ -1725,11 +1725,6 @@ static void svm_set_rflags(struct kvm_vc
 	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) {

@@ -5313,8 +5308,6 @@ static struct kvm_x86_ops svm_x86_ops __
 	.get_rflags = svm_get_rflags,
 	.set_rflags = svm_set_rflags,
 
-	.get_pkru = svm_get_pkru,
-
 	.tlb_flush = svm_flush_tlb,
 
 	.run = svm_vcpu_run,
arch/x86/kvm/vmx.c +8 -17
@@ -636,8 +636,6 @@ struct vcpu_vmx {
 
 	u64 current_tsc_ratio;
 
-	bool guest_pkru_valid;
-	u32 guest_pkru;
 	u32 host_pkru;
 
 	/*

@@ -2368,11 +2366,6 @@ static void vmx_set_rflags(struct kvm_vc
 	vmcs_writel(GUEST_RFLAGS, rflags);
 }
 
-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);

@@ -8860,8 +8853,10 @@ static void __noclone vmx_vcpu_run(struc
 	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_PKU) &&
+	    kvm_read_cr4_bits(vcpu, X86_CR4_PKE) &&
+	    vcpu->arch.pkru != vmx->host_pkru)
+		__write_pkru(vcpu->arch.pkru);
 
 	atomic_switch_perf_msrs(vmx);
 	debugctlmsr = get_debugctlmsr();

@@ -9009,13 +9004,11 @@ static void __noclone vmx_vcpu_run(struc
 	 * 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_PKU) &&
+	    kvm_read_cr4_bits(vcpu, X86_CR4_PKE)) {
+		vcpu->arch.pkru = __read_pkru();
+		if (vcpu->arch.pkru != vmx->host_pkru)
 			__write_pkru(vmx->host_pkru);
-		} else
-			vmx->guest_pkru_valid = false;
 	}
 
 	/*

@@ -11507,8 +11500,6 @@ static struct kvm_x86_ops vmx_x86_ops __
 	.get_rflags = vmx_get_rflags,
 	.set_rflags = vmx_set_rflags,
 
-	.get_pkru = vmx_get_pkru,
-
 	.tlb_flush = vmx_flush_tlb,
 
 	.run = vmx_vcpu_run,

Patches currently in stable-queue which might be from [email protected] are

queue-4.12/kvm-x86-block-guest-protection-keys-unless-the-host-has-them-enabled.patch queue-4.12/kvm-pkeys-do-not-use-pkru-value-in-vcpu-arch.guest_fpu.state.patch queue-4.12/kvm-x86-simplify-handling-of-pkru.patch