[PATCH v11 08/46] KVM: x86: hyper-v: Resurrect dedicated KVM_REQ_HV_TLB_FLUSH flag

Vitaly Kuznetsov
2022-10-04T12:41:34Z

In preparation to implementing fine-grained Hyper-V TLB flush and
L2 TLB flush, resurrect dedicated KVM_REQ_HV_TLB_FLUSH request bit. As
KVM_REQ_TLB_FLUSH_GUEST is a stronger operation, clear KVM_REQ_HV_TLB_FLUSH
request in kvm_vcpu_flush_tlb_guest().

The flush itself is temporary handled by kvm_vcpu_flush_tlb_guest().

No functional change intended.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
arch/x86/include/asm/kvm_host.h | 2 ++
arch/x86/kvm/hyperv.c | 4 ++--
arch/x86/kvm/svm/svm.c | 7 +++++++
arch/x86/kvm/x86.c | 9 +++++++++
4 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 504daf473092..45c390c804f0 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -108,6 +108,8 @@
KVM_ARCH_REQ_FLAGS(30, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
#define KVM_REQ_MMU_FREE_OBSOLETE_ROOTS \
KVM_ARCH_REQ_FLAGS(31, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
+#define KVM_REQ_HV_TLB_FLUSH \
+ KVM_ARCH_REQ_FLAGS(32, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)

#define CR0_RESERVED_BITS \
(~(unsigned long)(X86_CR0_PE | X86_CR0_MP | X86_CR0_EM | X86_CR0_TS \
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 0adf4a437e85..3c0f639f6a05 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1870,11 +1870,11 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
* analyze it here, flush TLB regardless of the specified address space.
*/
if (all_cpus) {
- kvm_make_all_cpus_request(kvm, KVM_REQ_TLB_FLUSH_GUEST);
+ kvm_make_all_cpus_request(kvm, KVM_REQ_HV_TLB_FLUSH);
} else {
sparse_set_to_vcpu_mask(kvm, sparse_banks, valid_bank_mask, vcpu_mask);

- kvm_make_vcpus_request_mask(kvm, KVM_REQ_TLB_FLUSH_GUEST, vcpu_mask);
+ kvm_make_vcpus_request_mask(kvm, KVM_REQ_HV_TLB_FLUSH, vcpu_mask);
}

ret_success:
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index dd599afc85f5..64c5d2bc863f 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3737,6 +3737,13 @@ static void svm_flush_tlb_current(struct kvm_vcpu *vcpu)
{
struct vcpu_svm *svm = to_svm(vcpu);

+ /*
+ * Unlike VMX, SVM doesn't provide a way to flush only NPT TLB entries.
+ * A TLB flush for the current ASID flushes both "host" and "guest" TLB
+ * entries, and thus is a superset of Hyper-V's fine grained flushing.
+ */
+ kvm_clear_request(KVM_REQ_HV_TLB_FLUSH, vcpu);
+
/*
* Flush only the current ASID even if the TLB flush was invoked via
* kvm_flush_remote_tlbs(). Although flushing remote TLBs requires all
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f1e3a4ec53ba..0539d216f760 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3404,6 +3404,12 @@ static void kvm_vcpu_flush_tlb_guest(struct kvm_vcpu *vcpu)
}

static_call(kvm_x86_flush_tlb_guest)(vcpu);
+
+ /*
+ * Flushing all "guest" TLB is always a superset of Hyper-V's fine
+ * grained flushing.
+ */
+ kvm_clear_request(KVM_REQ_HV_TLB_FLUSH, vcpu);
}

@@ -10478,6 +10484,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)

kvm_service_local_tlb_flush_requests(vcpu);

+ if (kvm_check_request(KVM_REQ_HV_TLB_FLUSH, vcpu))
+ kvm_vcpu_flush_tlb_guest(vcpu);
+
if (kvm_check_request(KVM_REQ_REPORT_TPR_ACCESS, vcpu)) {
vcpu->run->exit_reason = KVM_EXIT_TPR_ACCESS;
r = 0;
--
2.37.3