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KVM: x86/mmu: Honor NEED_RESCHED when zapping rmaps and blocking is allowed

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Convert kvm_unmap_gfn_range(), which is the helper that zaps rmap SPTEs in
response to an mmu_notifier invalidation, to use __kvm_rmap_zap_gfn_range()
and feed in range->may_block.  In other words, honor NEED_RESCHED by way of
cond_resched() when zapping rmaps.  This fixes a long-standing issue where
KVM could process an absurd number of rmap entries without ever yielding,
e.g. if an mmu_notifier fired on a PUD (or larger) range.

Opportunistically rename __kvm_zap_rmap() to kvm_zap_rmap(), and drop the
old kvm_zap_rmap().  Ideally, the shuffling would be done in a different
patch, but that just makes the compiler unhappy, e.g.

  arch/x86/kvm/mmu/mmu.c:1462:13: error: ‘kvm_zap_rmap’ defined but not used

Reported-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/20240809194335.1726916-14-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson
2024-08-09 12:43:25 -07:00
parent dd9eaad744
commit 548f87f667
1 changed files with 6 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
arch/x86/kvm/mmu/mmu.c
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@@ -1435,18 +1435,12 @@ static bool kvm_vcpu_write_protect_gfn(struct kvm_vcpu *vcpu, u64 gfn)
return kvm_mmu_slot_gfn_write_protect(vcpu->kvm, slot, gfn, PG_LEVEL_4K);
}
static bool __kvm_zap_rmap(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
const struct kvm_memory_slot *slot)
static bool kvm_zap_rmap(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
const struct kvm_memory_slot *slot)
{
return kvm_zap_all_rmap_sptes(kvm, rmap_head);
}
static bool kvm_zap_rmap(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
struct kvm_memory_slot *slot, gfn_t gfn, int level)
{
return __kvm_zap_rmap(kvm, rmap_head, slot);
}
struct slot_rmap_walk_iterator {
/* input fields. */
const struct kvm_memory_slot *slot;
@@ -1578,7 +1572,7 @@ static bool __kvm_rmap_zap_gfn_range(struct kvm *kvm,
gfn_t start, gfn_t end, bool can_yield,
bool flush)
{
return __walk_slot_rmaps(kvm, slot, __kvm_zap_rmap,
return __walk_slot_rmaps(kvm, slot, kvm_zap_rmap,
PG_LEVEL_4K, KVM_MAX_HUGEPAGE_LEVEL,
start, end - 1, can_yield, true, flush);
}
@@ -1607,7 +1601,9 @@ bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
bool flush = false;
if (kvm_memslots_have_rmaps(kvm))
flush = kvm_handle_gfn_range(kvm, range, kvm_zap_rmap);
flush = __kvm_rmap_zap_gfn_range(kvm, range->slot,
range->start, range->end,
range->may_block, flush);
if (tdp_mmu_enabled)
flush = kvm_tdp_mmu_unmap_gfn_range(kvm, range, flush);