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KVM: MMU: Make kvm_mmu_slot_remove_write_access() rmap based

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This makes it possible to release mmu_lock and reschedule conditionally
in a later patch.  Although this may increase the time needed to protect
the whole slot when we start dirty logging, the kernel should not allow
the userspace to trigger something that will hold a spinlock for such a
long time as tens of milliseconds: actually there is no limit since it
is roughly proportional to the number of guest pages.

Another point to note is that this patch removes the only user of
slot_bitmap which will cause some problems when we increase the number
of slots further.

Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
This commit is contained in:
Takuya Yoshikawa 2013-01-08 19:44:48 +09:00 committed by Gleb Natapov
parent 245c3912ea
commit b99db1d352
1 changed files with 15 additions and 13 deletions
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28
arch/x86/kvm/mmu.c
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@ -4172,25 +4172,27 @@ int kvm_mmu_setup(struct kvm_vcpu *vcpu)
void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot)
{
struct kvm_mmu_page *sp;
bool flush = false;
struct kvm_memory_slot *memslot;
gfn_t last_gfn;
int i;
list_for_each_entry(sp, &kvm->arch.active_mmu_pages, link) {
int i;
u64 *pt;
memslot = id_to_memslot(kvm->memslots, slot);
last_gfn = memslot->base_gfn + memslot->npages - 1;
if (!test_bit(slot, sp->slot_bitmap))
continue;
for (i = PT_PAGE_TABLE_LEVEL;
i < PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES; ++i) {
unsigned long *rmapp;
unsigned long last_index, index;
pt = sp->spt;
for (i = 0; i < PT64_ENT_PER_PAGE; ++i) {
if (!is_shadow_present_pte(pt[i]) ||
!is_last_spte(pt[i], sp->role.level))
continue;
rmapp = memslot->arch.rmap[i - PT_PAGE_TABLE_LEVEL];
last_index = gfn_to_index(last_gfn, memslot->base_gfn, i);
spte_write_protect(kvm, &pt[i], &flush, false);
for (index = 0; index <= last_index; ++index, ++rmapp) {
if (*rmapp)
__rmap_write_protect(kvm, rmapp, false);
}
}
kvm_flush_remote_tlbs(kvm);
}