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

From: Yang Zhang
Date: Thu Aug 24 2017 - 05:09:31 EST


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