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Subject[PATCH RFC 16/19] KVM: nVMX: hyper-v: Direct TLB flush
Date
Enable Direct TLB flush feature on nVMX when:
- Enlightened VMCS is in use.
- Direct TLB flush flag is enabled in eVMCS.
- Direct TLB flush is enabled in partition assist page.

Perform synthetic vmexit to L1 after processing TLB flush call upon
request (HV_VMX_SYNTHETIC_EXIT_REASON_TRAP_AFTER_FLUSH).

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
arch/x86/kvm/vmx/evmcs.c | 20 ++++++++++++++++++++
arch/x86/kvm/vmx/evmcs.h | 3 +++
arch/x86/kvm/vmx/nested.c | 16 ++++++++++++++++
3 files changed, 39 insertions(+)

diff --git a/arch/x86/kvm/vmx/evmcs.c b/arch/x86/kvm/vmx/evmcs.c
index 1705c4973636..cdf7ec5cb64c 100644
--- a/arch/x86/kvm/vmx/evmcs.c
+++ b/arch/x86/kvm/vmx/evmcs.c
@@ -6,6 +6,7 @@
#include "../hyperv.h"
#include "../cpuid.h"
#include "evmcs.h"
+#include "nested.h"
#include "vmcs.h"
#include "vmx.h"
#include "trace.h"
@@ -438,6 +439,25 @@ int nested_enable_evmcs(struct kvm_vcpu *vcpu,
return 0;
}

+bool nested_evmcs_direct_flush_enabled(struct kvm_vcpu *vcpu)
+{
+ struct vcpu_vmx *vmx = to_vmx(vcpu);
+ struct hv_enlightened_vmcs *evmcs = vmx->nested.hv_evmcs;
+ struct hv_vp_assist_page assist_page;
+
+ if (!evmcs)
+ return false;
+
+ if (!evmcs->hv_enlightenments_control.nested_flush_hypercall)
+ return false;
+
+ if (unlikely(!kvm_hv_get_assist_page(vcpu, &assist_page)))
+ return false;
+
+ return assist_page.nested_control.features.directhypercall;
+}
+
void vmx_post_hv_direct_flush(struct kvm_vcpu *vcpu)
{
+ nested_vmx_vmexit(vcpu, HV_VMX_SYNTHETIC_EXIT_REASON_TRAP_AFTER_FLUSH, 0, 0);
}
diff --git a/arch/x86/kvm/vmx/evmcs.h b/arch/x86/kvm/vmx/evmcs.h
index 8862692a4c5d..ab0949c22d2d 100644
--- a/arch/x86/kvm/vmx/evmcs.h
+++ b/arch/x86/kvm/vmx/evmcs.h
@@ -65,6 +65,8 @@ DECLARE_STATIC_KEY_FALSE(enable_evmcs);
#define EVMCS1_UNSUPPORTED_VMENTRY_CTRL (VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL)
#define EVMCS1_UNSUPPORTED_VMFUNC (VMX_VMFUNC_EPTP_SWITCHING)

+#define HV_VMX_SYNTHETIC_EXIT_REASON_TRAP_AFTER_FLUSH 0x10000031
+
struct evmcs_field {
u16 offset;
u16 clean_field;
@@ -244,6 +246,7 @@ int nested_enable_evmcs(struct kvm_vcpu *vcpu,
uint16_t *vmcs_version);
void nested_evmcs_filter_control_msr(u32 msr_index, u64 *pdata);
int nested_evmcs_check_controls(struct vmcs12 *vmcs12);
+bool nested_evmcs_direct_flush_enabled(struct kvm_vcpu *vcpu);
void vmx_post_hv_direct_flush(struct kvm_vcpu *vcpu);

#endif /* __KVM_X86_VMX_EVMCS_H */
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index a9fb6c63f849..3f908a8e5113 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -1168,6 +1168,17 @@ static void nested_vmx_transition_tlb_flush(struct kvm_vcpu *vcpu,
{
struct vcpu_vmx *vmx = to_vmx(vcpu);

+ /*
+ * KVM_REQ_HV_TLB_FLUSH flushes entries from either L1's VPID or
+ * L2's VPID upon request from the guest. Make sure we check for
+ * pending entries for the case when the request got misplaced (e.g.
+ * a transition from L2->L1 happened while processing Direct TLB flush
+ * request or vice versa). kvm_hv_vcpu_flush_tlb() will not flush
+ * anything if there are no requests in the corresponding buffer.
+ */
+ if (to_hv_vcpu(vcpu))
+ kvm_make_request(KVM_REQ_HV_TLB_FLUSH, vcpu);
+
/*
* If vmcs12 doesn't use VPID, L1 expects linear and combined mappings
* for *all* contexts to be flushed on VM-Enter/VM-Exit, i.e. it's a
@@ -5976,6 +5987,11 @@ static bool nested_vmx_l0_wants_exit(struct kvm_vcpu *vcpu,
* Handle L2's bus locks in L0 directly.
*/
return true;
+ case EXIT_REASON_VMCALL:
+ /* Hyper-V Direct TLB flush hypercall is handled by L0 */
+ return kvm_hv_direct_tlb_flush_exposed(vcpu) &&
+ nested_evmcs_direct_flush_enabled(vcpu) &&
+ kvm_hv_is_tlb_flush_hcall(vcpu);
default:
break;
}
--
2.35.1
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