lkml.org 
[lkml]   [2022]   [Mar]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH RFC 03/19] KVM: x86: hyper-v: Handle HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST{,EX} calls gently
Date
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@redhat.com>
---
arch/x86/kvm/hyperv.c | 141 ++++++++++++++++++++++++++++++++++++------
1 file changed, 121 insertions(+), 20 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index bc7e41fa5cd3..4c8a37bce71e 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1806,6 +1806,35 @@ static u64 kvm_get_sparse_vp_set(struct kvm *kvm, struct kvm_hv_hcall *hc,
var_cnt * sizeof(*sparse_banks));
}

+static int kvm_hv_get_tlbflush_entries(struct kvm *kvm, struct kvm_hv_hcall *hc, u64 entries[],
+ u32 data_offset, int consumed_xmm_halves)
+{
+ int i;
+
+ if (hc->fast) {
+ /*
+ * Each XMM holds two entries, but do not count halves that
+ * have already been consumed.
+ */
+ if (hc->rep_cnt > (2 * HV_HYPERCALL_MAX_XMM_REGISTERS - consumed_xmm_halves))
+ return -EINVAL;
+
+ for (i = 0; i < hc->rep_cnt; i++) {
+ int j = i + consumed_xmm_halves;
+
+ if (j % 2)
+ entries[i] = sse128_hi(hc->xmm[j / 2]);
+ else
+ entries[i] = sse128_lo(hc->xmm[j / 2]);
+ }
+
+ return 0;
+ }
+
+ return kvm_read_guest(kvm, hc->ingpa + data_offset,
+ entries, hc->rep_cnt * sizeof(entries[0]));
+}
+
static inline int hv_tlb_flush_ring_free(struct kvm_vcpu_hv *hv_vcpu,
int read_idx, int write_idx)
{
@@ -1815,12 +1844,14 @@ 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, bool flush_all,
+ u64 *entries, int count)
{
struct kvm_vcpu_hv_tlbflush_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;
@@ -1837,14 +1868,34 @@ 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 || flush_all) {
+ 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);
@@ -1854,15 +1905,47 @@ void kvm_hv_vcpu_flush_tlb(struct kvm_vcpu *vcpu)
{
struct kvm_vcpu_hv_tlbflush_ring *tlb_flush_ring;
struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
-
- kvm_vcpu_flush_tlb_guest(vcpu);
-
- if (!hv_vcpu)
+ struct kvm_vcpu_hv_tlbflush_entry *entry;
+ int read_idx, write_idx;
+ u64 address;
+ u32 count;
+ int i, j;
+
+ if (!tdp_enabled || !hv_vcpu) {
+ kvm_vcpu_flush_tlb_guest(vcpu);
return;
+ }

tlb_flush_ring = &hv_vcpu->tlb_flush_ring;
+ read_idx = READ_ONCE(tlb_flush_ring->read_idx);
+ write_idx = READ_ONCE(tlb_flush_ring->write_idx);
+
+ /* Pairs with smp_wmb() in hv_tlb_flush_ring_enqueue() */
+ smp_rmb();

- tlb_flush_ring->read_idx = tlb_flush_ring->write_idx;
+ 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)
@@ -1871,12 +1954,13 @@ 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);
+ u64 entries[KVM_HV_TLB_FLUSH_RING_SIZE - 2];
u64 valid_bank_mask;
u64 sparse_banks[KVM_HV_MAX_SPARSE_VCPU_SET_BITS];
struct kvm_vcpu *v;
unsigned long i;
- bool all_cpus;
-
+ bool all_cpus, all_addr;
+ int data_offset = 0, consumed_xmm_halves = 0;
/*
* The Hyper-V TLFS doesn't allow more than 64 sparse banks, e.g. the
* valid mask is a u64. Fail the build if KVM's max allowed number of
@@ -1891,10 +1975,12 @@ 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,
@@ -1918,10 +2004,12 @@ 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,
@@ -1937,25 +2025,38 @@ 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, 2, sparse_banks,
- offsetof(struct hv_tlb_flush_ex,
- hv_vp_set.bank_contents)))
+ if (kvm_get_sparse_vp_set(kvm, hc, consumed_xmm_halves,
+ sparse_banks, 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 > (KVM_HV_TLB_FLUSH_RING_SIZE - 2)) {
+ all_addr = true;
+ } else {
+ if (kvm_hv_get_tlbflush_entries(kvm, hc, entries,
+ data_offset, consumed_xmm_halves))
return HV_STATUS_INVALID_HYPERCALL_INPUT;
+ all_addr = false;
}

-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, all_addr, entries, hc->rep_cnt);

kvm_make_all_cpus_request(kvm, KVM_REQ_HV_TLB_FLUSH);
} else {
@@ -1965,7 +2066,7 @@ 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, all_addr, entries, hc->rep_cnt);
}

kvm_make_vcpus_request_mask(kvm, KVM_REQ_HV_TLB_FLUSH, vcpu_mask);
--
2.35.1
\
 
 \ /
  Last update: 2022-03-07 15:52    [W:0.228 / U:0.220 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site