From: Avi Kivity Date: Sun, 30 Dec 2007 10:29:05 +0000 (+0200) Subject: KVM: MMU: Avoid calling gfn_to_page() in mmu_set_spte() X-Git-Tag: v2.6.25-rc1~1138^2~10 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d7824fff896a1698a07a8046dc362f4500c302f7;p=linux-2.6 KVM: MMU: Avoid calling gfn_to_page() in mmu_set_spte() Since gfn_to_page() is a sleeping function, and we want to make the core mmu spinlocked, we need to pass the page from the walker context (which can sleep) to the shadow context (which cannot). [marcelo: avoid recursive locking of mmap_sem] Signed-off-by: Avi Kivity --- diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 3b91227969..c0b757be7b 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -890,11 +890,10 @@ struct page *gva_to_page(struct kvm_vcpu *vcpu, gva_t gva) static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *shadow_pte, unsigned pt_access, unsigned pte_access, int user_fault, int write_fault, int dirty, - int *ptwrite, gfn_t gfn) + int *ptwrite, gfn_t gfn, struct page *page) { u64 spte; int was_rmapped = is_rmap_pte(*shadow_pte); - struct page *page; pgprintk("%s: spte %llx access %x write_fault %d" " user_fault %d gfn %lx\n", @@ -912,8 +911,6 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *shadow_pte, if (!(pte_access & ACC_EXEC_MASK)) spte |= PT64_NX_MASK; - page = gfn_to_page(vcpu->kvm, gfn); - spte |= PT_PRESENT_MASK; if (pte_access & ACC_USER_MASK) spte |= PT_USER_MASK; @@ -979,6 +976,11 @@ static int __nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn) int level = PT32E_ROOT_LEVEL; hpa_t table_addr = vcpu->arch.mmu.root_hpa; int pt_write = 0; + struct page *page; + + down_read(¤t->mm->mmap_sem); + page = gfn_to_page(vcpu->kvm, gfn); + up_read(¤t->mm->mmap_sem); for (; ; level--) { u32 index = PT64_INDEX(v, level); @@ -989,7 +991,7 @@ static int __nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn) if (level == 1) { mmu_set_spte(vcpu, &table[index], ACC_ALL, ACC_ALL, - 0, write, 1, &pt_write, gfn); + 0, write, 1, &pt_write, gfn, page); return pt_write || is_io_pte(table[index]); } @@ -1005,6 +1007,7 @@ static int __nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn) NULL); if (!new_table) { pgprintk("nonpaging_map: ENOMEM\n"); + kvm_release_page_clean(page); return -ENOMEM; } @@ -1347,6 +1350,43 @@ static bool last_updated_pte_accessed(struct kvm_vcpu *vcpu) return !!(spte && (*spte & PT_ACCESSED_MASK)); } +static void mmu_guess_page_from_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa, + const u8 *new, int bytes) +{ + gfn_t gfn; + int r; + u64 gpte = 0; + + if (bytes != 4 && bytes != 8) + return; + + /* + * Assume that the pte write on a page table of the same type + * as the current vcpu paging mode. This is nearly always true + * (might be false while changing modes). Note it is verified later + * by update_pte(). + */ + if (is_pae(vcpu)) { + /* Handle a 32-bit guest writing two halves of a 64-bit gpte */ + if ((bytes == 4) && (gpa % 4 == 0)) { + r = kvm_read_guest(vcpu->kvm, gpa & ~(u64)7, &gpte, 8); + if (r) + return; + memcpy((void *)&gpte + (gpa % 8), new, 4); + } else if ((bytes == 8) && (gpa % 8 == 0)) { + memcpy((void *)&gpte, new, 8); + } + } else { + if ((bytes == 4) && (gpa % 4 == 0)) + memcpy((void *)&gpte, new, 4); + } + if (!is_present_pte(gpte)) + return; + gfn = (gpte & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT; + vcpu->arch.update_pte.gfn = gfn; + vcpu->arch.update_pte.page = gfn_to_page(vcpu->kvm, gfn); +} + void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa, const u8 *new, int bytes) { @@ -1367,6 +1407,7 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa, int npte; pgprintk("%s: gpa %llx bytes %d\n", __FUNCTION__, gpa, bytes); + mmu_guess_page_from_pte_write(vcpu, gpa, new, bytes); mutex_lock(&vcpu->kvm->lock); ++vcpu->kvm->stat.mmu_pte_write; kvm_mmu_audit(vcpu, "pre pte write"); @@ -1437,6 +1478,10 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa, } kvm_mmu_audit(vcpu, "post pte write"); mutex_unlock(&vcpu->kvm->lock); + if (vcpu->arch.update_pte.page) { + kvm_release_page_clean(vcpu->arch.update_pte.page); + vcpu->arch.update_pte.page = NULL; + } } int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva) diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index 136a65d72b..3d7846ba26 100644 --- a/arch/x86/kvm/paging_tmpl.h +++ b/arch/x86/kvm/paging_tmpl.h @@ -245,6 +245,7 @@ static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *page, { pt_element_t gpte; unsigned pte_access; + struct page *npage; gpte = *(const pt_element_t *)pte; if (~gpte & (PT_PRESENT_MASK | PT_ACCESSED_MASK)) { @@ -256,8 +257,14 @@ static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *page, return; pgprintk("%s: gpte %llx spte %p\n", __FUNCTION__, (u64)gpte, spte); pte_access = page->role.access & FNAME(gpte_access)(vcpu, gpte); + if (gpte_to_gfn(gpte) != vcpu->arch.update_pte.gfn) + return; + npage = vcpu->arch.update_pte.page; + if (!npage) + return; + get_page(npage); mmu_set_spte(vcpu, spte, page->role.access, pte_access, 0, 0, - gpte & PT_DIRTY_MASK, NULL, gpte_to_gfn(gpte)); + gpte & PT_DIRTY_MASK, NULL, gpte_to_gfn(gpte), npage); } /* @@ -265,7 +272,8 @@ static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *page, */ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, struct guest_walker *walker, - int user_fault, int write_fault, int *ptwrite) + int user_fault, int write_fault, int *ptwrite, + struct page *page) { hpa_t shadow_addr; int level; @@ -321,8 +329,10 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, r = kvm_read_guest_atomic(vcpu->kvm, walker->pte_gpa[level - 2], &curr_pte, sizeof(curr_pte)); - if (r || curr_pte != walker->ptes[level - 2]) + if (r || curr_pte != walker->ptes[level - 2]) { + kvm_release_page_clean(page); return NULL; + } } shadow_addr = __pa(shadow_page->spt); shadow_pte = shadow_addr | PT_PRESENT_MASK | PT_ACCESSED_MASK @@ -333,7 +343,7 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, mmu_set_spte(vcpu, shadow_ent, access, walker->pte_access & access, user_fault, write_fault, walker->ptes[walker->level-1] & PT_DIRTY_MASK, - ptwrite, walker->gfn); + ptwrite, walker->gfn, page); return shadow_ent; } @@ -362,6 +372,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u64 *shadow_pte; int write_pt = 0; int r; + struct page *page; pgprintk("%s: addr %lx err %x\n", __FUNCTION__, addr, error_code); kvm_mmu_audit(vcpu, "pre page fault"); @@ -388,9 +399,11 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, return 0; } + page = gfn_to_page(vcpu->kvm, walker.gfn); + mutex_lock(&vcpu->kvm->lock); shadow_pte = FNAME(fetch)(vcpu, addr, &walker, user_fault, write_fault, - &write_pt); + &write_pt, page); pgprintk("%s: shadow pte %p %llx ptwrite %d\n", __FUNCTION__, shadow_pte, *shadow_pte, write_pt); diff --git a/include/asm-x86/kvm_host.h b/include/asm-x86/kvm_host.h index 44b89259f6..20597bc167 100644 --- a/include/asm-x86/kvm_host.h +++ b/include/asm-x86/kvm_host.h @@ -224,6 +224,11 @@ struct kvm_vcpu_arch { int last_pt_write_count; u64 *last_pte_updated; + struct { + gfn_t gfn; /* presumed gfn during guest pte update */ + struct page *page; /* page corresponding to that gfn */ + } update_pte; + struct i387_fxsave_struct host_fx_image; struct i387_fxsave_struct guest_fx_image;