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KVM: Introduce kvm_unmap_hva_range() for kvm_mmu_notifier_invalidate_range_start() 

When we tested KVM under memory pressure, with THP enabled on the host,
we noticed that MMU notifier took a long time to invalidate huge pages.

Since the invalidation was done with mmu_lock held, it not only wasted
the CPU but also made the host harder to respond.

This patch mitigates this by using kvm_handle_hva_range().

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Cc: Alexander Graf <agraf@suse.de>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Takuya Yoshikawa 2012-07-02 17:56:33 +09:00 committed by Marcelo Tosatti
parent 84504ef386
commit b3ae209697
5 changed files with 16 additions and 2 deletions
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2
arch/powerpc/include/asm/kvm_host.h
View File

@ -52,6 +52,8 @@
struct kvm;
extern int kvm_unmap_hva(struct kvm *kvm, unsigned long hva);
extern int kvm_unmap_hva_range(struct kvm *kvm,
unsigned long start, unsigned long end);
extern int kvm_age_hva(struct kvm *kvm, unsigned long hva);
extern int kvm_test_age_hva(struct kvm *kvm, unsigned long hva);
extern void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte);

7
arch/powerpc/kvm/book3s_64_mmu_hv.c
View File

@ -870,6 +870,13 @@ int kvm_unmap_hva(struct kvm *kvm, unsigned long hva)
return 0;
}
int kvm_unmap_hva_range(struct kvm *kvm, unsigned long start, unsigned long end)
{
if (kvm->arch.using_mmu_notifiers)
kvm_handle_hva_range(kvm, start, end, kvm_unmap_rmapp);
return 0;
}
static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
unsigned long gfn)
{

1
arch/x86/include/asm/kvm_host.h
View File

@ -944,6 +944,7 @@ extern bool kvm_rebooting;
#define KVM_ARCH_WANT_MMU_NOTIFIER
int kvm_unmap_hva(struct kvm *kvm, unsigned long hva);
int kvm_unmap_hva_range(struct kvm *kvm, unsigned long start, unsigned long end);
int kvm_age_hva(struct kvm *kvm, unsigned long hva);
int kvm_test_age_hva(struct kvm *kvm, unsigned long hva);
void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte);

5
arch/x86/kvm/mmu.c
View File

@ -1324,6 +1324,11 @@ int kvm_unmap_hva(struct kvm *kvm, unsigned long hva)
return kvm_handle_hva(kvm, hva, 0, kvm_unmap_rmapp);
}
int kvm_unmap_hva_range(struct kvm *kvm, unsigned long start, unsigned long end)
{
return kvm_handle_hva_range(kvm, start, end, 0, kvm_unmap_rmapp);
}
void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte)
{
kvm_handle_hva(kvm, hva, (unsigned long)&pte, kvm_set_pte_rmapp);

3
virt/kvm/kvm_main.c
View File

@ -332,8 +332,7 @@ static void kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
* count is also read inside the mmu_lock critical section.
*/
kvm->mmu_notifier_count++;
for (; start < end; start += PAGE_SIZE)
need_tlb_flush |= kvm_unmap_hva(kvm, start);
need_tlb_flush = kvm_unmap_hva_range(kvm, start, end);
need_tlb_flush |= kvm->tlbs_dirty;
/* we've to flush the tlb before the pages can be freed */
if (need_tlb_flush)