KVM: x86: hyper-v: Create a separate fifo for L2 TLB flush

To handle L2 TLB flush requests, KVM needs to use a separate fifo from
regular (L1) Hyper-V TLB flush requests: e.g. when a request to flush
something in L2 is made, the target vCPU can transition from L2 to L1,
receive a request to flush a GVA for L1 and then try to enter L2 back.
The first request needs to be processed at this point. Similarly,
requests to flush GVAs in L1 must wait until L2 exits to L1.

No functional change as KVM doesn't handle L2 TLB flush requests from
L2 yet.

Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20221101145426.251680-18-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 3e35dcf40dc7cc59afcdf2a1811bf60e6fb541a4..89f9c98ff4456c21ca5408f29409610951ae4ecd 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -631,6 +631,12 @@ struct kvm_vcpu_hv_synic {
  */
 #define KVM_HV_TLB_FLUSHALL_ENTRY  ((u64)-1)
 
+enum hv_tlb_flush_fifos {
+       HV_L1_TLB_FLUSH_FIFO,
+       HV_L2_TLB_FLUSH_FIFO,
+       HV_NR_TLB_FLUSH_FIFOS,
+};
+
 struct kvm_vcpu_hv_tlb_flush_fifo {
        spinlock_t write_lock;
        DECLARE_KFIFO(entries, u64, KVM_HV_TLB_FLUSH_FIFO_SIZE);
@@ -658,7 +664,7 @@ struct kvm_vcpu_hv {
                u32 nested_ebx; /* HYPERV_CPUID_NESTED_FEATURES.EBX */
        } cpuid_cache;
 
-       struct kvm_vcpu_hv_tlb_flush_fifo tlb_flush_fifo;
+       struct kvm_vcpu_hv_tlb_flush_fifo tlb_flush_fifo[HV_NR_TLB_FLUSH_FIFOS];
 };
 
 /* Xen HVM per vcpu emulation context */

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 0bfa59838e0a58aa58b75bc95db03ee0f31ba075..9898463103032d0cc9d319c439a777f3963c8946 100644 (file)
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -956,8 +956,10 @@ int kvm_hv_vcpu_init(struct kvm_vcpu *vcpu)
 
        hv_vcpu->vp_index = vcpu->vcpu_idx;
 
-       INIT_KFIFO(hv_vcpu->tlb_flush_fifo.entries);
-       spin_lock_init(&hv_vcpu->tlb_flush_fifo.write_lock);
+       for (i = 0; i < HV_NR_TLB_FLUSH_FIFOS; i++) {
+               INIT_KFIFO(hv_vcpu->tlb_flush_fifo[i].entries);
+               spin_lock_init(&hv_vcpu->tlb_flush_fifo[i].write_lock);
+       }
 
        return 0;
 }
@@ -1839,7 +1841,8 @@ static void hv_tlb_flush_enqueue(struct kvm_vcpu *vcpu, u64 *entries, int count)
        if (!hv_vcpu)
                return;
 
-       tlb_flush_fifo = &hv_vcpu->tlb_flush_fifo;
+       /* kvm_hv_flush_tlb() is not ready to handle requests for L2s yet */
+       tlb_flush_fifo = &hv_vcpu->tlb_flush_fifo[HV_L1_TLB_FLUSH_FIFO];
 
        spin_lock(&tlb_flush_fifo->write_lock);
 
@@ -1874,7 +1877,7 @@ int kvm_hv_vcpu_flush_tlb(struct kvm_vcpu *vcpu)
        if (!tdp_enabled || !hv_vcpu)
                return -EINVAL;
 
-       tlb_flush_fifo = &hv_vcpu->tlb_flush_fifo;
+       tlb_flush_fifo = kvm_hv_get_tlb_flush_fifo(vcpu, is_guest_mode(vcpu));
 
        count = kfifo_out(&tlb_flush_fifo->entries, entries, KVM_HV_TLB_FLUSH_FIFO_SIZE);
 

diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
index f79edf9234cd4c13ecb08eb99c2cae68940932f2..8942e8c6c912edf60c36b4cf5c723f659a13a35e 100644 (file)
--- a/arch/x86/kvm/hyperv.h
+++ b/arch/x86/kvm/hyperv.h
@@ -22,6 +22,7 @@
 #define __ARCH_X86_KVM_HYPERV_H__
 
 #include <linux/kvm_host.h>
+#include "x86.h"
 
 /* "Hv#1" signature */
 #define HYPERV_CPUID_SIGNATURE_EAX 0x31237648
@@ -151,15 +152,27 @@ int kvm_vm_ioctl_hv_eventfd(struct kvm *kvm, struct kvm_hyperv_eventfd *args);
 int kvm_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
                     struct kvm_cpuid_entry2 __user *entries);
 
+static inline struct kvm_vcpu_hv_tlb_flush_fifo *kvm_hv_get_tlb_flush_fifo(struct kvm_vcpu *vcpu,
+                                                                          bool is_guest_mode)
+{
+       struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
+       int i = is_guest_mode ? HV_L2_TLB_FLUSH_FIFO :
+                               HV_L1_TLB_FLUSH_FIFO;
+
+       /* KVM does not handle L2 TLB flush requests yet */
+       WARN_ON_ONCE(i != HV_L1_TLB_FLUSH_FIFO);
+
+       return &hv_vcpu->tlb_flush_fifo[i];
+}
+
 static inline void kvm_hv_vcpu_purge_flush_tlb(struct kvm_vcpu *vcpu)
 {
        struct kvm_vcpu_hv_tlb_flush_fifo *tlb_flush_fifo;
-       struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
 
-       if (!hv_vcpu || !kvm_check_request(KVM_REQ_HV_TLB_FLUSH, vcpu))
+       if (!to_hv_vcpu(vcpu) || !kvm_check_request(KVM_REQ_HV_TLB_FLUSH, vcpu))
                return;
 
-       tlb_flush_fifo = &hv_vcpu->tlb_flush_fifo;
+       tlb_flush_fifo = kvm_hv_get_tlb_flush_fifo(vcpu, is_guest_mode(vcpu));
 
        kfifo_reset_out(&tlb_flush_fifo->entries);
 }