Re: [PATCH v2 08/12] KVM: MMU: fast prefetch spte on invlpg path

[Marcelo Tosatti]

On Tue, Aug 02, 2011 at 07:10:54PM +0800, Xiao Guangrong wrote:
> Fast prefetch spte for the unsync shadow page on invlpg path
> 
> Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxx>
> ---
>  arch/x86/include/asm/kvm_host.h |    3 +--
>  arch/x86/kvm/mmu.c              |   37 +++++++++++++++----------------------
>  arch/x86/kvm/paging_tmpl.h      |   23 ++++++++++-------------
>  arch/x86/kvm/x86.c              |    4 ++--
>  4 files changed, 28 insertions(+), 39 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index b256660..2c08458 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -456,7 +456,6 @@ struct kvm_arch {
>  	unsigned int n_requested_mmu_pages;
>  	unsigned int n_max_mmu_pages;
>  	unsigned int indirect_shadow_pages;
> -	atomic_t invlpg_counter;
>  	struct hlist_head mmu_page_hash[KVM_NUM_MMU_PAGES];
>  	/*
>  	 * Hash table of struct kvm_mmu_page.
> @@ -749,7 +748,7 @@ int fx_init(struct kvm_vcpu *vcpu);
>  void kvm_mmu_flush_tlb(struct kvm_vcpu *vcpu);
>  void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
>  		       const u8 *new, int bytes,
> -		       bool guest_initiated, bool page_table_written);
> +		       bool page_table_written);
>  int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva);
>  void __kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu);
>  int kvm_mmu_load(struct kvm_vcpu *vcpu);
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 8e97ffa..5517115 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -3526,7 +3526,7 @@ static bool last_updated_pte_accessed(struct kvm_vcpu *vcpu)
>  
>  void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
>  		       const u8 *new, int bytes,
> -		       bool guest_initiated, bool page_table_written)
> +		       bool page_table_written)
>  {
>  	gfn_t gfn = gpa >> PAGE_SHIFT;
>  	union kvm_mmu_page_role mask = { .word = 0 };
> @@ -3535,7 +3535,7 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
>  	LIST_HEAD(invalid_list);
>  	u64 entry, gentry, *spte;
>  	unsigned pte_size, page_offset, misaligned, quadrant, offset;
> -	int level, npte, invlpg_counter, r, flooded = 0;
> +	int level, npte, r, flooded = 0;
>  	bool remote_flush, local_flush, zap_page;
>  
>  	/*
> @@ -3550,19 +3550,16 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
>  
>  	pgprintk("%s: gpa %llx bytes %d\n", __func__, gpa, bytes);
>  
> -	invlpg_counter = atomic_read(&vcpu->kvm->arch.invlpg_counter);
> -
>  	/*
>  	 * Assume that the pte write on a page table of the same type
>  	 * as the current vcpu paging mode since we update the sptes only
>  	 * when they have the same mode.
>  	 */
> -	if ((is_pae(vcpu) && bytes == 4) || !new) {
> +	if (is_pae(vcpu) && bytes == 4) {
>  		/* Handle a 32-bit guest writing two halves of a 64-bit gpte */
> -		if (is_pae(vcpu)) {
> -			gpa &= ~(gpa_t)7;
> -			bytes = 8;
> -		}
> +		gpa &= ~(gpa_t)7;
> +		bytes = 8;
> +
>  		r = kvm_read_guest(vcpu->kvm, gpa, &gentry, min(bytes, 8));
>  		if (r)
>  			gentry = 0;
> @@ -3588,22 +3585,18 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
>  	 */
>  	mmu_topup_memory_caches(vcpu);
>  	spin_lock(&vcpu->kvm->mmu_lock);
> -	if (atomic_read(&vcpu->kvm->arch.invlpg_counter) != invlpg_counter)
> -		gentry = 0;
>  	kvm_mmu_free_some_pages(vcpu);
>  	++vcpu->kvm->stat.mmu_pte_write;
>  	trace_kvm_mmu_audit(vcpu, AUDIT_PRE_PTE_WRITE);
> -	if (guest_initiated) {
> -		if (gfn == vcpu->arch.last_pt_write_gfn
> -		    && !last_updated_pte_accessed(vcpu)) {
> -			++vcpu->arch.last_pt_write_count;
> -			if (vcpu->arch.last_pt_write_count >= 3)
> -				flooded = 1;
> -		} else {
> -			vcpu->arch.last_pt_write_gfn = gfn;
> -			vcpu->arch.last_pt_write_count = 1;
> -			vcpu->arch.last_pte_updated = NULL;
> -		}
> +	if (gfn == vcpu->arch.last_pt_write_gfn
> +	    && !last_updated_pte_accessed(vcpu)) {
> +		++vcpu->arch.last_pt_write_count;
> +		if (vcpu->arch.last_pt_write_count >= 3)
> +			flooded = 1;
> +	} else {
> +		vcpu->arch.last_pt_write_gfn = gfn;
> +		vcpu->arch.last_pt_write_count = 1;
> +		vcpu->arch.last_pte_updated = NULL;
>  	}
>  
>  	mask.cr0_wp = mask.cr4_pae = mask.nxe = 1;
> diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
> index 0f915b5..3466229 100644
> --- a/arch/x86/kvm/paging_tmpl.h
> +++ b/arch/x86/kvm/paging_tmpl.h
> @@ -666,20 +666,22 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva)
>  {
>  	struct kvm_shadow_walk_iterator iterator;
>  	struct kvm_mmu_page *sp;
> -	gpa_t pte_gpa = -1;
>  	int level;
>  	u64 *sptep;
>  
>  	vcpu_clear_mmio_info(vcpu, gva);
> +	mmu_topup_memory_caches(vcpu);

Should handle failure.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/