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KVM: x86: hyper-v: L2 TLB flush

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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.

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: <20221101145426.251680-24-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Vitaly Kuznetsov 2022-11-01 15:54:01 +01:00 committed by Paolo Bonzini
parent 3c9eb0655f
commit c58a318f60
3 changed files with 80 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

80
arch/x86/kvm/hyperv.c
View File

@ -34,6 +34,7 @@
#include <linux/eventfd.h>
#include <asm/apicdef.h>
#include <asm/mshyperv.h>
#include <trace/events/kvm.h>
#include "trace.h"
@ -1832,18 +1833,16 @@ 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 flush_all_entry = KVM_HV_TLB_FLUSHALL_ENTRY;
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(&tlb_flush_fifo->write_lock);
/*
@ -1912,6 +1911,7 @@ 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
@ -1962,7 +1962,8 @@ 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;
@ -1993,7 +1994,7 @@ 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 !=
@ -2037,19 +2038,57 @@ 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);
@ -2239,10 +2278,25 @@ 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)
{
u32 tlb_lock_count = 0;
int ret;
if (hv_result_success(result) && is_guest_mode(vcpu) &&
kvm_hv_is_tlb_flush_hcall(vcpu) &&
kvm_read_guest(vcpu->kvm, to_hv_vcpu(vcpu)->nested.pa_page_gpa,
&tlb_lock_count, sizeof(tlb_lock_count)))
result = HV_STATUS_INVALID_HYPERCALL_INPUT;
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 (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)

3
arch/x86/kvm/hyperv.h
View File

@ -159,9 +159,6 @@ static inline struct kvm_vcpu_hv_tlb_flush_fifo *kvm_hv_get_tlb_flush_fifo(struc
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];
}

21
arch/x86/kvm/trace.h
View File

@ -1547,38 +1547,41 @@ 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(
@ -1586,12 +1589,14 @@ 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)" : "")
);
/*