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Subject[PATCH v6 17/38] KVM: x86: hyper-v: L2 TLB flush
Date
Handle L2 TLB flush requests by going through all vCPUs and checking
whether there are vCPUs running the same VM_ID with a VP_ID specified
in the requests. Perform synthetic exit to L2 upon finish.

Note, while checking VM_ID/VP_ID of running vCPUs seem to be a bit
racy, we count on the fact that KVM flushes the whole L2 VPID upon
transition. Also, KVM_REQ_HV_TLB_FLUSH request needs to be done upon
transition between L1 and L2 to make sure all pending requests are
always processed.

For the reference, Hyper-V TLFS refers to the feature as "Direct
Virtual Flush".

Note, nVMX/nSVM code does not handle VMCALL/VMMCALL from L2 yet.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
arch/x86/kvm/hyperv.c | 84 +++++++++++++++++++++++++++++++++++--------
arch/x86/kvm/hyperv.h | 14 ++++----
arch/x86/kvm/trace.h | 21 ++++++-----
arch/x86/kvm/x86.c | 4 +--
4 files changed, 91 insertions(+), 32 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 3075e9661696..740190917c1c 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -34,6 +34,7 @@
#include <linux/eventfd.h>

#include <asm/apicdef.h>
+#include <asm/mshyperv.h>
#include <trace/events/kvm.h>

#include "trace.h"
@@ -1835,9 +1836,10 @@ static int kvm_hv_get_tlb_flush_entries(struct kvm *kvm, struct kvm_hv_hcall *hc
entries, consumed_xmm_halves, offset);
}

-static void hv_tlb_flush_enqueue(struct kvm_vcpu *vcpu, u64 *entries, int count)
+static void hv_tlb_flush_enqueue(struct kvm_vcpu *vcpu,
+ struct kvm_vcpu_hv_tlb_flush_fifo *tlb_flush_fifo,
+ u64 *entries, int count)
{
- struct kvm_vcpu_hv_tlb_flush_fifo *tlb_flush_fifo;
struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
u64 entry = KVM_HV_TLB_FLUSHALL_ENTRY;
unsigned long flags;
@@ -1845,9 +1847,6 @@ static void hv_tlb_flush_enqueue(struct kvm_vcpu *vcpu, u64 *entries, int count)
if (!hv_vcpu)
return;

- /* 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_irqsave(&tlb_flush_fifo->write_lock, flags);

/*
@@ -1883,7 +1882,7 @@ void kvm_hv_vcpu_flush_tlb(struct kvm_vcpu *vcpu)
return;
}

- tlb_flush_fifo = kvm_hv_get_tlb_flush_fifo(vcpu);
+ 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);

@@ -1916,6 +1915,7 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
struct hv_tlb_flush_ex flush_ex;
struct hv_tlb_flush flush;
DECLARE_BITMAP(vcpu_mask, KVM_MAX_VCPUS);
+ struct kvm_vcpu_hv_tlb_flush_fifo *tlb_flush_fifo;
/*
* Normally, there can be no more than 'KVM_HV_TLB_FLUSH_FIFO_SIZE'
* entries on the TLB flush fifo. The last entry, however, needs to be
@@ -1959,7 +1959,8 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
}

trace_kvm_hv_flush_tlb(flush.processor_mask,
- flush.address_space, flush.flags);
+ flush.address_space, flush.flags,
+ is_guest_mode(vcpu));

valid_bank_mask = BIT_ULL(0);
sparse_banks[0] = flush.processor_mask;
@@ -1990,7 +1991,7 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
trace_kvm_hv_flush_tlb_ex(flush_ex.hv_vp_set.valid_bank_mask,
flush_ex.hv_vp_set.format,
flush_ex.address_space,
- flush_ex.flags);
+ flush_ex.flags, is_guest_mode(vcpu));

valid_bank_mask = flush_ex.hv_vp_set.valid_bank_mask;
all_cpus = flush_ex.hv_vp_set.format !=
@@ -2028,19 +2029,57 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
* vcpu->arch.cr3 may not be up-to-date for running vCPUs so we can't
* analyze it here, flush TLB regardless of the specified address space.
*/
- if (all_cpus) {
- kvm_for_each_vcpu(i, v, kvm)
- hv_tlb_flush_enqueue(v, tlb_flush_entries, hc->rep_cnt);
+ if (all_cpus && !is_guest_mode(vcpu)) {
+ kvm_for_each_vcpu(i, v, kvm) {
+ tlb_flush_fifo = kvm_hv_get_tlb_flush_fifo(v, false);
+ hv_tlb_flush_enqueue(v, tlb_flush_fifo,
+ tlb_flush_entries, hc->rep_cnt);
+ }

kvm_make_all_cpus_request(kvm, KVM_REQ_HV_TLB_FLUSH);
- } else {
+ } else if (!is_guest_mode(vcpu)) {
sparse_set_to_vcpu_mask(kvm, sparse_banks, valid_bank_mask, vcpu_mask);

for_each_set_bit(i, vcpu_mask, KVM_MAX_VCPUS) {
v = kvm_get_vcpu(kvm, i);
if (!v)
continue;
- hv_tlb_flush_enqueue(v, tlb_flush_entries, hc->rep_cnt);
+ tlb_flush_fifo = kvm_hv_get_tlb_flush_fifo(v, false);
+ hv_tlb_flush_enqueue(v, tlb_flush_fifo,
+ tlb_flush_entries, hc->rep_cnt);
+ }
+
+ kvm_make_vcpus_request_mask(kvm, KVM_REQ_HV_TLB_FLUSH, vcpu_mask);
+ } else {
+ struct kvm_vcpu_hv *hv_v;
+
+ bitmap_zero(vcpu_mask, KVM_MAX_VCPUS);
+
+ kvm_for_each_vcpu(i, v, kvm) {
+ hv_v = to_hv_vcpu(v);
+
+ /*
+ * The following check races with nested vCPUs entering/exiting
+ * and/or migrating between L1's vCPUs, however the only case when
+ * KVM *must* flush the TLB is when the target L2 vCPU keeps
+ * running on the same L1 vCPU from the moment of the request until
+ * kvm_hv_flush_tlb() returns. TLB is fully flushed in all other
+ * cases, e.g. when the target L2 vCPU migrates to a different L1
+ * vCPU or when the corresponding L1 vCPU temporary switches to a
+ * different L2 vCPU while the request is being processed.
+ */
+ if (!hv_v || hv_v->nested.vm_id != hv_vcpu->nested.vm_id)
+ continue;
+
+ if (!all_cpus &&
+ !hv_is_vp_in_sparse_set(hv_v->nested.vp_id, valid_bank_mask,
+ sparse_banks))
+ continue;
+
+ __set_bit(i, vcpu_mask);
+ tlb_flush_fifo = kvm_hv_get_tlb_flush_fifo(v, true);
+ hv_tlb_flush_enqueue(v, tlb_flush_fifo,
+ tlb_flush_entries, hc->rep_cnt);
}

kvm_make_vcpus_request_mask(kvm, KVM_REQ_HV_TLB_FLUSH, vcpu_mask);
@@ -2228,10 +2267,27 @@ static void kvm_hv_hypercall_set_result(struct kvm_vcpu *vcpu, u64 result)

static int kvm_hv_hypercall_complete(struct kvm_vcpu *vcpu, u64 result)
{
+ int ret;
+
trace_kvm_hv_hypercall_done(result);
kvm_hv_hypercall_set_result(vcpu, result);
++vcpu->stat.hypercalls;
- return kvm_skip_emulated_instruction(vcpu);
+ ret = kvm_skip_emulated_instruction(vcpu);
+
+ if (unlikely(hv_result_success(result) && is_guest_mode(vcpu)
+ && kvm_hv_is_tlb_flush_hcall(vcpu))) {
+ struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
+ u32 tlb_lock_count;
+
+ if (unlikely(kvm_read_guest(vcpu->kvm, hv_vcpu->nested.pa_page_gpa,
+ &tlb_lock_count, sizeof(tlb_lock_count))))
+ kvm_inject_gp(vcpu, 0);
+
+ if (tlb_lock_count)
+ kvm_x86_ops.nested_ops->hv_inject_synthetic_vmexit_post_tlb_flush(vcpu);
+ }
+
+ return ret;
}

static int kvm_hv_hypercall_complete_userspace(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
index dc46c5ed5d18..7778b3a5913c 100644
--- a/arch/x86/kvm/hyperv.h
+++ b/arch/x86/kvm/hyperv.h
@@ -148,26 +148,24 @@ 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)
+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(vcpu) ? HV_L1_TLB_FLUSH_FIFO :
- HV_L2_TLB_FLUSH_FIFO;
-
- /* KVM does not handle L2 TLB flush requests yet */
- WARN_ON_ONCE(i != HV_L1_TLB_FLUSH_FIFO);
+ int i = is_guest_mode ? HV_L2_TLB_FLUSH_FIFO :
+ HV_L1_TLB_FLUSH_FIFO;

return &hv_vcpu->tlb_flush_fifo[i];
}

-static inline void kvm_hv_vcpu_empty_flush_tlb(struct kvm_vcpu *vcpu)
+static inline void kvm_hv_vcpu_empty_flush_tlb(struct kvm_vcpu *vcpu, bool is_guest_mode)
{
struct kvm_vcpu_hv_tlb_flush_fifo *tlb_flush_fifo;

if (!to_hv_vcpu(vcpu) || !kvm_check_request(KVM_REQ_HV_TLB_FLUSH, vcpu))
return;

- tlb_flush_fifo = kvm_hv_get_tlb_flush_fifo(vcpu);
+ tlb_flush_fifo = kvm_hv_get_tlb_flush_fifo(vcpu, is_guest_mode);

kfifo_reset_out(&tlb_flush_fifo->entries);
}
diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
index fd28dd40b813..f5e5b8f0342c 100644
--- a/arch/x86/kvm/trace.h
+++ b/arch/x86/kvm/trace.h
@@ -1510,38 +1510,41 @@ TRACE_EVENT(kvm_hv_timer_state,
* Tracepoint for kvm_hv_flush_tlb.
*/
TRACE_EVENT(kvm_hv_flush_tlb,
- TP_PROTO(u64 processor_mask, u64 address_space, u64 flags),
- TP_ARGS(processor_mask, address_space, flags),
+ TP_PROTO(u64 processor_mask, u64 address_space, u64 flags, bool guest_mode),
+ TP_ARGS(processor_mask, address_space, flags, guest_mode),

TP_STRUCT__entry(
__field(u64, processor_mask)
__field(u64, address_space)
__field(u64, flags)
+ __field(bool, guest_mode)
),

TP_fast_assign(
__entry->processor_mask = processor_mask;
__entry->address_space = address_space;
__entry->flags = flags;
+ __entry->guest_mode = guest_mode;
),

- TP_printk("processor_mask 0x%llx address_space 0x%llx flags 0x%llx",
+ TP_printk("processor_mask 0x%llx address_space 0x%llx flags 0x%llx %s",
__entry->processor_mask, __entry->address_space,
- __entry->flags)
+ __entry->flags, __entry->guest_mode ? "(L2)" : "")
);

/*
* Tracepoint for kvm_hv_flush_tlb_ex.
*/
TRACE_EVENT(kvm_hv_flush_tlb_ex,
- TP_PROTO(u64 valid_bank_mask, u64 format, u64 address_space, u64 flags),
- TP_ARGS(valid_bank_mask, format, address_space, flags),
+ TP_PROTO(u64 valid_bank_mask, u64 format, u64 address_space, u64 flags, bool guest_mode),
+ TP_ARGS(valid_bank_mask, format, address_space, flags, guest_mode),

TP_STRUCT__entry(
__field(u64, valid_bank_mask)
__field(u64, format)
__field(u64, address_space)
__field(u64, flags)
+ __field(bool, guest_mode)
),

TP_fast_assign(
@@ -1549,12 +1552,14 @@ TRACE_EVENT(kvm_hv_flush_tlb_ex,
__entry->format = format;
__entry->address_space = address_space;
__entry->flags = flags;
+ __entry->guest_mode = guest_mode;
),

TP_printk("valid_bank_mask 0x%llx format 0x%llx "
- "address_space 0x%llx flags 0x%llx",
+ "address_space 0x%llx flags 0x%llx %s",
__entry->valid_bank_mask, __entry->format,
- __entry->address_space, __entry->flags)
+ __entry->address_space, __entry->flags,
+ __entry->guest_mode ? "(L2)" : "")
);

/*
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 805db43c2829..8e945500ef50 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3355,12 +3355,12 @@ void kvm_service_local_tlb_flush_requests(struct kvm_vcpu *vcpu)
{
if (kvm_check_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu)) {
kvm_vcpu_flush_tlb_current(vcpu);
- kvm_hv_vcpu_empty_flush_tlb(vcpu);
+ kvm_hv_vcpu_empty_flush_tlb(vcpu, is_guest_mode(vcpu));
}

if (kvm_check_request(KVM_REQ_TLB_FLUSH_GUEST, vcpu)) {
kvm_vcpu_flush_tlb_guest(vcpu);
- kvm_hv_vcpu_empty_flush_tlb(vcpu);
+ kvm_hv_vcpu_empty_flush_tlb(vcpu, is_guest_mode(vcpu));
} else if (kvm_check_request(KVM_REQ_HV_TLB_FLUSH, vcpu)) {
kvm_hv_vcpu_flush_tlb(vcpu);
}
--
2.35.3
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