[PATCH v10 05/39] KVM: x86: hyper-v: Handle HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST{,EX} calls gently

Vitaly Kuznetsov
2022-09-21T15:25:20Z

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 fifo to queue the requests.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
arch/x86/kvm/hyperv.c | 101 ++++++++++++++++++++++++++++++++++++------
1 file changed, 88 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index fb0f7342fccf..d5a329cebcc6 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1800,33 +1800,82 @@ static u64 kvm_get_sparse_vp_set(struct kvm *kvm, struct kvm_hv_hcall *hc,
sparse_banks, consumed_xmm_halves, offset);
}

-static void hv_tlb_flush_enqueue(struct kvm_vcpu *vcpu)
+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 void hv_tlb_flush_enqueue(struct kvm_vcpu *vcpu, 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;
+ unsigned long flags;

if (!hv_vcpu)
return;

tlb_flush_fifo = &hv_vcpu->tlb_flush_fifo;

- kfifo_in_spinlocked(&tlb_flush_fifo->entries, &flush_all_entry,
- 1, &tlb_flush_fifo->write_lock);
+ spin_lock_irqsave(&tlb_flush_fifo->write_lock, flags);
+
+ /*
+ * All entries should fit on the fifo 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 && entries && count < kfifo_avail(&tlb_flush_fifo->entries)) {
+ WARN_ON(kfifo_in(&tlb_flush_fifo->entries, entries, count) != count);
+ goto out_unlock;
+ }
+
+ /*
+ * Note: full fifo always contains 'flush all' entry, no need to check the
+ * return value.
+ */
+ kfifo_in(&tlb_flush_fifo->entries, &flush_all_entry, 1);
+
+out_unlock:
+ spin_unlock_irqrestore(&tlb_flush_fifo->write_lock, flags);
}

void kvm_hv_vcpu_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);
+ u64 entries[KVM_HV_TLB_FLUSH_FIFO_SIZE];
+ int i, j, count;
+ gva_t gva;

- kvm_vcpu_flush_tlb_guest(vcpu);
-
- if (!hv_vcpu)
+ if (!tdp_enabled || !hv_vcpu) {
+ kvm_vcpu_flush_tlb_guest(vcpu);
return;
+ }

tlb_flush_fifo = &hv_vcpu->tlb_flush_fifo;

+ count = kfifo_out(&tlb_flush_fifo->entries, entries, KVM_HV_TLB_FLUSH_FIFO_SIZE);
+
+ for (i = 0; i < count; i++) {
+ if (entries[i] == KVM_HV_TLB_FLUSHALL_ENTRY)
+ goto out_flush_all;
+
+ /*
+ * Lower 12 bits of 'address' encode the number of additional
+ * pages to flush.
+ */
+ gva = entries[i] & PAGE_MASK;
+ for (j = 0; j < (entries[i] & ~PAGE_MASK) + 1; j++)
+ static_call(kvm_x86_flush_tlb_gva)(vcpu, gva + j * PAGE_SIZE);
+
+ ++vcpu->stat.tlb_flush;
+ }
+ return;
+
+out_flush_all:
+ kvm_vcpu_flush_tlb_guest(vcpu);
kfifo_reset_out(&tlb_flush_fifo->entries);
}

@@ -1836,11 +1885,21 @@ 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_FIFO_SIZE'
+ * entries on the TLB flush fifo. The last entry, 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_FIFO_SIZE - 1];
+ 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
@@ -1856,10 +1915,12 @@ 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,
@@ -1883,10 +1944,12 @@ 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,
@@ -1902,25 +1965,37 @@ 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_enqueue(v);
+ hv_tlb_flush_enqueue(v, tlb_flush_entries, hc->rep_cnt);

kvm_make_all_cpus_request(kvm, KVM_REQ_HV_TLB_FLUSH);
} else {
@@ -1930,7 +2005,7 @@ 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_enqueue(v);
+ hv_tlb_flush_enqueue(v, tlb_flush_entries, hc->rep_cnt);
}

kvm_make_vcpus_request_mask(kvm, KVM_REQ_HV_TLB_FLUSH, vcpu_mask);
--
2.37.3