From 6fd01b711bee96ce3356f7b6f370ab708e37504b Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Wed, 12 Sep 2012 20:46:56 +0300 Subject: [PATCH] KVM: MMU: Optimize is_last_gpte() Instead of branchy code depending on level, gpte.ps, and mmu configuration, prepare everything in a bitmap during mode changes and look it up during runtime. Reviewed-by: Xiao Guangrong Signed-off-by: Avi Kivity --- arch/x86/include/asm/kvm_host.h | 7 +++++++ arch/x86/kvm/mmu.c | 31 +++++++++++++++++++++++++++++++ arch/x86/kvm/mmu.h | 3 ++- arch/x86/kvm/paging_tmpl.h | 20 +------------------- 4 files changed, 41 insertions(+), 20 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 3318bde206a5..43aeb9422839 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -298,6 +298,13 @@ struct kvm_mmu { u64 *lm_root; u64 rsvd_bits_mask[2][4]; + /* + * Bitmap: bit set = last pte in walk + * index[0:1]: level (zero-based) + * index[2]: pte.ps + */ + u8 last_pte_bitmap; + bool nx; u64 pdptrs[4]; /* pae */ diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 9c6188931f87..d289fee1ffb8 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -3447,6 +3447,15 @@ static inline unsigned gpte_access(struct kvm_vcpu *vcpu, u64 gpte) return access; } +static inline bool is_last_gpte(struct kvm_mmu *mmu, unsigned level, unsigned gpte) +{ + unsigned index; + + index = level - 1; + index |= (gpte & PT_PAGE_SIZE_MASK) >> (PT_PAGE_SIZE_SHIFT - 2); + return mmu->last_pte_bitmap & (1 << index); +} + #define PTTYPE 64 #include "paging_tmpl.h" #undef PTTYPE @@ -3548,6 +3557,24 @@ static void update_permission_bitmask(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu } } +static void update_last_pte_bitmap(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu) +{ + u8 map; + unsigned level, root_level = mmu->root_level; + const unsigned ps_set_index = 1 << 2; /* bit 2 of index: ps */ + + if (root_level == PT32E_ROOT_LEVEL) + --root_level; + /* PT_PAGE_TABLE_LEVEL always terminates */ + map = 1 | (1 << ps_set_index); + for (level = PT_DIRECTORY_LEVEL; level <= root_level; ++level) { + if (level <= PT_PDPE_LEVEL + && (mmu->root_level >= PT32E_ROOT_LEVEL || is_pse(vcpu))) + map |= 1 << (ps_set_index | (level - 1)); + } + mmu->last_pte_bitmap = map; +} + static int paging64_init_context_common(struct kvm_vcpu *vcpu, struct kvm_mmu *context, int level) @@ -3557,6 +3584,7 @@ static int paging64_init_context_common(struct kvm_vcpu *vcpu, reset_rsvds_bits_mask(vcpu, context); update_permission_bitmask(vcpu, context); + update_last_pte_bitmap(vcpu, context); ASSERT(is_pae(vcpu)); context->new_cr3 = paging_new_cr3; @@ -3586,6 +3614,7 @@ static int paging32_init_context(struct kvm_vcpu *vcpu, reset_rsvds_bits_mask(vcpu, context); update_permission_bitmask(vcpu, context); + update_last_pte_bitmap(vcpu, context); context->new_cr3 = paging_new_cr3; context->page_fault = paging32_page_fault; @@ -3647,6 +3676,7 @@ static int init_kvm_tdp_mmu(struct kvm_vcpu *vcpu) } update_permission_bitmask(vcpu, context); + update_last_pte_bitmap(vcpu, context); return 0; } @@ -3724,6 +3754,7 @@ static int init_kvm_nested_mmu(struct kvm_vcpu *vcpu) } update_permission_bitmask(vcpu, g_context); + update_last_pte_bitmap(vcpu, g_context); return 0; } diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h index 584660775d08..69871080e866 100644 --- a/arch/x86/kvm/mmu.h +++ b/arch/x86/kvm/mmu.h @@ -20,7 +20,8 @@ #define PT_ACCESSED_MASK (1ULL << PT_ACCESSED_SHIFT) #define PT_DIRTY_SHIFT 6 #define PT_DIRTY_MASK (1ULL << PT_DIRTY_SHIFT) -#define PT_PAGE_SIZE_MASK (1ULL << 7) +#define PT_PAGE_SIZE_SHIFT 7 +#define PT_PAGE_SIZE_MASK (1ULL << PT_PAGE_SIZE_SHIFT) #define PT_PAT_MASK (1ULL << 7) #define PT_GLOBAL_MASK (1ULL << 8) #define PT64_NX_SHIFT 63 diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index 1b4c14d235a0..134ea7b1c585 100644 --- a/arch/x86/kvm/paging_tmpl.h +++ b/arch/x86/kvm/paging_tmpl.h @@ -103,24 +103,6 @@ static int FNAME(cmpxchg_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, return (ret != orig_pte); } -static bool FNAME(is_last_gpte)(struct guest_walker *walker, - struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, - pt_element_t gpte) -{ - if (walker->level == PT_PAGE_TABLE_LEVEL) - return true; - - if ((walker->level == PT_DIRECTORY_LEVEL) && is_large_pte(gpte) && - (PTTYPE == 64 || is_pse(vcpu))) - return true; - - if ((walker->level == PT_PDPE_LEVEL) && is_large_pte(gpte) && - (mmu->root_level == PT64_ROOT_LEVEL)) - return true; - - return false; -} - static int FNAME(update_accessed_dirty_bits)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, struct guest_walker *walker, @@ -247,7 +229,7 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker, pte_access = pt_access & gpte_access(vcpu, pte); walker->ptes[walker->level - 1] = pte; - } while (!FNAME(is_last_gpte)(walker, vcpu, mmu, pte)); + } while (!is_last_gpte(mmu, walker->level, pte)); eperm |= permission_fault(mmu, pte_access, access); if (unlikely(eperm)) { -- GitLab