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Message-Id: <20220414132013.1588929-5-vkuznets@redhat.com>
Date: Thu, 14 Apr 2022 15:19:43 +0200
From: Vitaly Kuznetsov <vkuznets@...hat.com>
To: kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Cc: Sean Christopherson <seanjc@...gle.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Michael Kelley <mikelley@...rosoft.com>,
Siddharth Chandrasekaran <sidcha@...zon.de>,
linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v3 04/34] KVM: x86: hyper-v: Handle HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST{,EX} calls gently
Currently, HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST{,EX} calls are handled
the exact same way as HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE{,EX}: by
flushing the whole VPID and this is sub-optimal. Switch to handling
these requests with 'flush_tlb_gva()' hooks instead. Use the newly
introduced TLB flush ring to queue the requests.
Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
arch/x86/kvm/hyperv.c | 132 ++++++++++++++++++++++++++++++++++++------
1 file changed, 115 insertions(+), 17 deletions(-)
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index d66c27fd1e8a..759e1a16e5c3 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1805,6 +1805,13 @@ static u64 kvm_get_sparse_vp_set(struct kvm *kvm, struct kvm_hv_hcall *hc,
sparse_banks, consumed_xmm_halves, offset);
}
+static int kvm_hv_get_tlb_flush_entries(struct kvm *kvm, struct kvm_hv_hcall *hc, u64 entries[],
+ int consumed_xmm_halves, gpa_t offset)
+{
+ return kvm_hv_get_hc_data(kvm, hc, hc->rep_cnt, hc->rep_cnt,
+ entries, consumed_xmm_halves, offset);
+}
+
static inline int hv_tlb_flush_ring_free(struct kvm_vcpu_hv *hv_vcpu,
int read_idx, int write_idx)
{
@@ -1814,12 +1821,13 @@ static inline int hv_tlb_flush_ring_free(struct kvm_vcpu_hv *hv_vcpu,
return read_idx - write_idx - 1;
}
-static void hv_tlb_flush_ring_enqueue(struct kvm_vcpu *vcpu)
+static void hv_tlb_flush_ring_enqueue(struct kvm_vcpu *vcpu, u64 *entries, int count)
{
struct kvm_vcpu_hv_tlb_flush_ring *tlb_flush_ring;
struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
int ring_free, write_idx, read_idx;
unsigned long flags;
+ int i;
if (!hv_vcpu)
return;
@@ -1845,14 +1853,34 @@ static void hv_tlb_flush_ring_enqueue(struct kvm_vcpu *vcpu)
if (!ring_free)
goto out_unlock;
- tlb_flush_ring->entries[write_idx].addr = 0;
- tlb_flush_ring->entries[write_idx].flush_all = 1;
/*
- * Advance write index only after filling in the entry to
- * synchronize with lockless reader.
+ * All entries should fit on the ring leaving one free for 'flush all'
+ * entry in case another request comes in. In case there's not enough
+ * space, just put 'flush all' entry there.
+ */
+ if (!count || count >= ring_free - 1 || !entries) {
+ tlb_flush_ring->entries[write_idx].addr = 0;
+ tlb_flush_ring->entries[write_idx].flush_all = 1;
+ /*
+ * Advance write index only after filling in the entry to
+ * synchronize with lockless reader.
+ */
+ smp_wmb();
+ tlb_flush_ring->write_idx = (write_idx + 1) % KVM_HV_TLB_FLUSH_RING_SIZE;
+ goto out_unlock;
+ }
+
+ for (i = 0; i < count; i++) {
+ tlb_flush_ring->entries[write_idx].addr = entries[i];
+ tlb_flush_ring->entries[write_idx].flush_all = 0;
+ write_idx = (write_idx + 1) % KVM_HV_TLB_FLUSH_RING_SIZE;
+ }
+ /*
+ * Advance write index only after filling in the entry to synchronize
+ * with lockless reader.
*/
smp_wmb();
- tlb_flush_ring->write_idx = (write_idx + 1) % KVM_HV_TLB_FLUSH_RING_SIZE;
+ tlb_flush_ring->write_idx = write_idx;
out_unlock:
spin_unlock_irqrestore(&tlb_flush_ring->write_lock, flags);
@@ -1862,15 +1890,58 @@ void kvm_hv_vcpu_flush_tlb(struct kvm_vcpu *vcpu)
{
struct kvm_vcpu_hv_tlb_flush_ring *tlb_flush_ring;
struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
+ struct kvm_vcpu_hv_tlb_flush_entry *entry;
+ int read_idx, write_idx;
+ u64 address;
+ u32 count;
+ int i, j;
- kvm_vcpu_flush_tlb_guest(vcpu);
-
- if (!hv_vcpu)
+ if (!tdp_enabled || !hv_vcpu) {
+ kvm_vcpu_flush_tlb_guest(vcpu);
return;
+ }
tlb_flush_ring = &hv_vcpu->tlb_flush_ring;
- tlb_flush_ring->read_idx = tlb_flush_ring->write_idx;
+ /*
+ * TLB flush must be performed on the target vCPU so 'read_idx'
+ * (AKA 'tail') cannot change underneath, the compiler is free
+ * to re-read it.
+ */
+ read_idx = tlb_flush_ring->read_idx;
+
+ /*
+ * 'write_idx' (AKA 'head') can be concurently updated by a different
+ * vCPU so we must be sure it's read once.
+ */
+ write_idx = READ_ONCE(tlb_flush_ring->write_idx);
+
+ /* Pairs with smp_wmb() in hv_tlb_flush_ring_enqueue() */
+ smp_rmb();
+
+ for (i = read_idx; i != write_idx; i = (i + 1) % KVM_HV_TLB_FLUSH_RING_SIZE) {
+ entry = &tlb_flush_ring->entries[i];
+
+ if (entry->flush_all)
+ goto out_flush_all;
+
+ /*
+ * Lower 12 bits of 'address' encode the number of additional
+ * pages to flush.
+ */
+ address = entry->addr & PAGE_MASK;
+ count = (entry->addr & ~PAGE_MASK) + 1;
+ for (j = 0; j < count; j++)
+ static_call(kvm_x86_flush_tlb_gva)(vcpu, address + j * PAGE_SIZE);
+ }
+ ++vcpu->stat.tlb_flush;
+ goto out_empty_ring;
+
+out_flush_all:
+ kvm_vcpu_flush_tlb_guest(vcpu);
+
+out_empty_ring:
+ tlb_flush_ring->read_idx = write_idx;
}
static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
@@ -1879,11 +1950,22 @@ 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);
+ /*
+ * Normally, there can be no more than 'KVM_HV_TLB_FLUSH_RING_SIZE - 1'
+ * entries on the TLB Flush ring as when 'read_idx == write_idx' the
+ * ring is considered as empty. The last entry on the ring, however,
+ * needs to be always left free for 'flush all' entry which gets placed
+ * when there is not enough space to put all the requested entries.
+ */
+ u64 __tlb_flush_entries[KVM_HV_TLB_FLUSH_RING_SIZE - 2];
+ u64 *tlb_flush_entries;
u64 valid_bank_mask;
u64 sparse_banks[KVM_HV_MAX_SPARSE_VCPU_SET_BITS];
struct kvm_vcpu *v;
unsigned long i;
bool all_cpus;
+ int consumed_xmm_halves = 0;
+ gpa_t data_offset;
/*
* The Hyper-V TLFS doesn't allow more than 64 sparse banks, e.g. the
@@ -1899,10 +1981,12 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
flush.address_space = hc->ingpa;
flush.flags = hc->outgpa;
flush.processor_mask = sse128_lo(hc->xmm[0]);
+ consumed_xmm_halves = 1;
} else {
if (unlikely(kvm_read_guest(kvm, hc->ingpa,
&flush, sizeof(flush))))
return HV_STATUS_INVALID_HYPERCALL_INPUT;
+ data_offset = sizeof(flush);
}
trace_kvm_hv_flush_tlb(flush.processor_mask,
@@ -1926,10 +2010,12 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
flush_ex.flags = hc->outgpa;
memcpy(&flush_ex.hv_vp_set,
&hc->xmm[0], sizeof(hc->xmm[0]));
+ consumed_xmm_halves = 2;
} else {
if (unlikely(kvm_read_guest(kvm, hc->ingpa, &flush_ex,
sizeof(flush_ex))))
return HV_STATUS_INVALID_HYPERCALL_INPUT;
+ data_offset = sizeof(flush_ex);
}
trace_kvm_hv_flush_tlb_ex(flush_ex.hv_vp_set.valid_bank_mask,
@@ -1945,25 +2031,37 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
return HV_STATUS_INVALID_HYPERCALL_INPUT;
if (all_cpus)
- goto do_flush;
+ goto read_flush_entries;
if (!hc->var_cnt)
goto ret_success;
- if (kvm_get_sparse_vp_set(kvm, hc, sparse_banks, 2,
- offsetof(struct hv_tlb_flush_ex,
- hv_vp_set.bank_contents)))
+ if (kvm_get_sparse_vp_set(kvm, hc, sparse_banks, consumed_xmm_halves,
+ data_offset))
+ return HV_STATUS_INVALID_HYPERCALL_INPUT;
+ data_offset += hc->var_cnt * sizeof(sparse_banks[0]);
+ consumed_xmm_halves += hc->var_cnt;
+ }
+
+read_flush_entries:
+ if (hc->code == HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE ||
+ hc->code == HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX ||
+ hc->rep_cnt > ARRAY_SIZE(__tlb_flush_entries)) {
+ tlb_flush_entries = NULL;
+ } else {
+ if (kvm_hv_get_tlb_flush_entries(kvm, hc, __tlb_flush_entries,
+ consumed_xmm_halves, data_offset))
return HV_STATUS_INVALID_HYPERCALL_INPUT;
+ tlb_flush_entries = __tlb_flush_entries;
}
-do_flush:
/*
* 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_ring_enqueue(v);
+ hv_tlb_flush_ring_enqueue(v, tlb_flush_entries, hc->rep_cnt);
kvm_make_all_cpus_request(kvm, KVM_REQ_HV_TLB_FLUSH);
} else {
@@ -1973,7 +2071,7 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
v = kvm_get_vcpu(kvm, i);
if (!v)
continue;
- hv_tlb_flush_ring_enqueue(v);
+ hv_tlb_flush_ring_enqueue(v, tlb_flush_entries, hc->rep_cnt);
}
kvm_make_vcpus_request_mask(kvm, KVM_REQ_HV_TLB_FLUSH, vcpu_mask);
--
2.35.1
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