[PATCH v3 06/11] KVM: VMX: Invalidate hv_tlb_eptp to denote an EPTP mismatch

From: Sean Christopherson
Date: Tue Oct 27 2020 - 17:24:02 EST


Drop the dedicated 'ept_pointers_match' field in favor of stuffing
'hv_tlb_eptp' with INVALID_PAGE to mark it as invalid, i.e. to denote
that there is at least one EPTP mismatch. Use a local variable to
track whether or not a mismatch is detected so that hv_tlb_eptp can be
used to skip redundant flushes.

No functional change intended.

Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
arch/x86/kvm/vmx/vmx.c | 35 +++++++++++++++++++++++------------
arch/x86/kvm/vmx/vmx.h | 7 -------
2 files changed, 23 insertions(+), 19 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 17b228c4ba19..25a714cda662 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -500,32 +500,44 @@ static int hv_remote_flush_tlb_with_range(struct kvm *kvm,
{
struct kvm_vmx *kvm_vmx = to_kvm_vmx(kvm);
struct kvm_vcpu *vcpu;
- int ret = 0, i;
+ int ret = 0, i, nr_unique_valid_eptps;
u64 tmp_eptp;

spin_lock(&kvm_vmx->ept_pointer_lock);

- if (kvm_vmx->ept_pointers_match != EPT_POINTERS_MATCH) {
- kvm_vmx->ept_pointers_match = EPT_POINTERS_MATCH;
- kvm_vmx->hv_tlb_eptp = INVALID_PAGE;
+ if (!VALID_PAGE(kvm_vmx->hv_tlb_eptp)) {
+ nr_unique_valid_eptps = 0;

+ /*
+ * Flush all valid EPTPs, and see if all vCPUs have converged
+ * on a common EPTP, in which case future flushes can skip the
+ * loop and flush the common EPTP.
+ */
kvm_for_each_vcpu(i, vcpu, kvm) {
tmp_eptp = to_vmx(vcpu)->ept_pointer;
if (!VALID_PAGE(tmp_eptp) ||
tmp_eptp == kvm_vmx->hv_tlb_eptp)
continue;

- if (!VALID_PAGE(kvm_vmx->hv_tlb_eptp))
+ /*
+ * Set the tracked EPTP to the first valid EPTP. Keep
+ * this EPTP for the entirety of the loop even if more
+ * EPTPs are encountered as a low effort optimization
+ * to avoid flushing the same (first) EPTP again.
+ */
+ if (++nr_unique_valid_eptps == 1)
kvm_vmx->hv_tlb_eptp = tmp_eptp;
- else
- kvm_vmx->ept_pointers_match
- = EPT_POINTERS_MISMATCH;

ret |= hv_remote_flush_eptp(tmp_eptp, range);
}
- if (kvm_vmx->ept_pointers_match == EPT_POINTERS_MISMATCH)
+
+ /*
+ * The optimized flush of a single EPTP can't be used if there
+ * are multiple valid EPTPs (obviously).
+ */
+ if (nr_unique_valid_eptps > 1)
kvm_vmx->hv_tlb_eptp = INVALID_PAGE;
- } else if (VALID_PAGE(kvm_vmx->hv_tlb_eptp)) {
+ } else {
ret = hv_remote_flush_eptp(kvm_vmx->hv_tlb_eptp, range);
}

@@ -3060,8 +3072,7 @@ static void vmx_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t root_hpa,
if (kvm_x86_ops.tlb_remote_flush) {
spin_lock(&to_kvm_vmx(kvm)->ept_pointer_lock);
to_vmx(vcpu)->ept_pointer = eptp;
- to_kvm_vmx(kvm)->ept_pointers_match
- = EPT_POINTERS_CHECK;
+ to_kvm_vmx(kvm)->hv_tlb_eptp = INVALID_PAGE;
spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock);
}

diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 9a25e83f8b96..cecc2a641e19 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -288,12 +288,6 @@ struct vcpu_vmx {
} shadow_msr_intercept;
};

-enum ept_pointers_status {
- EPT_POINTERS_CHECK = 0,
- EPT_POINTERS_MATCH = 1,
- EPT_POINTERS_MISMATCH = 2
-};
-
struct kvm_vmx {
struct kvm kvm;

@@ -302,7 +296,6 @@ struct kvm_vmx {
gpa_t ept_identity_map_addr;

hpa_t hv_tlb_eptp;
- enum ept_pointers_status ept_pointers_match;
spinlock_t ept_pointer_lock;
};

--
2.28.0