On 19/10/2015 08:13, Takuya Yoshikawa wrote:
> Commit fd1369021878 ("KVM: x86: MMU: Move mapping_level_dirty_bitmap()
> call in mapping_level()") forgot to initialize force_pt_level to false
> in FNAME(page_fault)() before calling mapping_level() like
> nonpaging_map() does. This can sometimes result in forcing page table
> level mapping unnecessarily.
>
> Fix this and move the first *force_pt_level check in mapping_level()
> before kvm_vcpu_gfn_to_memslot() call to make it a bit clearer that
> the variable must be initialized before mapping_level() gets called.
>
> This change can also avoid calling kvm_vcpu_gfn_to_memslot() when
> !check_hugepage_cache_consistency() check in tdp_page_fault() forces
> page table level mapping.
>
> Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@xxxxxxxxxxxxx>
> ---
> arch/x86/kvm/mmu.c | 7 ++++---
> arch/x86/kvm/paging_tmpl.h | 2 +-
> 2 files changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index dd2a7c6..7d85bca 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -886,10 +886,11 @@ static int mapping_level(struct kvm_vcpu *vcpu, gfn_t large_gfn,
> int host_level, level, max_level;
> struct kvm_memory_slot *slot;
>
> - slot = kvm_vcpu_gfn_to_memslot(vcpu, large_gfn);
> + if (unlikely(*force_pt_level))
> + return PT_PAGE_TABLE_LEVEL;
>
> - if (likely(!*force_pt_level))
> - *force_pt_level = !memslot_valid_for_gpte(slot, true);
> + slot = kvm_vcpu_gfn_to_memslot(vcpu, large_gfn);
> + *force_pt_level = !memslot_valid_for_gpte(slot, true);
> if (unlikely(*force_pt_level))
> return PT_PAGE_TABLE_LEVEL;
>
> diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
> index bf39d0f..b41faa9 100644
> --- a/arch/x86/kvm/paging_tmpl.h
> +++ b/arch/x86/kvm/paging_tmpl.h
> @@ -698,7 +698,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code,
> int r;
> pfn_t pfn;
> int level = PT_PAGE_TABLE_LEVEL;
> - bool force_pt_level;
> + bool force_pt_level = false;
> unsigned long mmu_seq;
> bool map_writable, is_self_change_mapping;
>
>
Looks good, thanks.
Paolo
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