From 612819c3c6e67bac8fceaa7cc402f13b1b63f7e4 Mon Sep 17 00:00:00 2001 From: Marcelo Tosatti Date: Fri, 22 Oct 2010 14:18:18 -0200 Subject: [PATCH] KVM: propagate fault r/w information to gup(), allow read-only memory As suggested by Andrea, pass r/w error code to gup(), upgrading read fault to writable if host pte allows it. Signed-off-by: Marcelo Tosatti Signed-off-by: Avi Kivity --- arch/x86/kvm/mmu.c | 27 ++++++++++++-------- arch/x86/kvm/paging_tmpl.h | 13 +++++++--- include/linux/kvm_host.h | 5 +++- virt/kvm/kvm_main.c | 51 ++++++++++++++++++++++++++++++-------- 4 files changed, 71 insertions(+), 25 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 99433943170..53509f5973d 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -2216,7 +2216,7 @@ static void direct_pte_prefetch(struct kvm_vcpu *vcpu, u64 *sptep) } static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write, - int level, gfn_t gfn, pfn_t pfn) + int map_writable, int level, gfn_t gfn, pfn_t pfn) { struct kvm_shadow_walk_iterator iterator; struct kvm_mmu_page *sp; @@ -2225,9 +2225,13 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write, for_each_shadow_entry(vcpu, (u64)gfn << PAGE_SHIFT, iterator) { if (iterator.level == level) { - mmu_set_spte(vcpu, iterator.sptep, ACC_ALL, ACC_ALL, + unsigned pte_access = ACC_ALL; + + if (!map_writable) + pte_access &= ~ACC_WRITE_MASK; + mmu_set_spte(vcpu, iterator.sptep, ACC_ALL, pte_access, 0, write, 1, &pt_write, - level, gfn, pfn, false, true); + level, gfn, pfn, false, map_writable); direct_pte_prefetch(vcpu, iterator.sptep); ++vcpu->stat.pf_fixed; break; @@ -2288,6 +2292,7 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn) int level; pfn_t pfn; unsigned long mmu_seq; + bool map_writable; level = mapping_level(vcpu, gfn); @@ -2302,7 +2307,7 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn) mmu_seq = vcpu->kvm->mmu_notifier_seq; smp_rmb(); - pfn = gfn_to_pfn(vcpu->kvm, gfn); + pfn = gfn_to_pfn_prot(vcpu->kvm, gfn, write, &map_writable); /* mmio */ if (is_error_pfn(pfn)) @@ -2312,7 +2317,7 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn) if (mmu_notifier_retry(vcpu, mmu_seq)) goto out_unlock; kvm_mmu_free_some_pages(vcpu); - r = __direct_map(vcpu, v, write, level, gfn, pfn); + r = __direct_map(vcpu, v, write, map_writable, level, gfn, pfn); spin_unlock(&vcpu->kvm->mmu_lock); @@ -2611,11 +2616,11 @@ static bool can_do_async_pf(struct kvm_vcpu *vcpu) } static bool try_async_pf(struct kvm_vcpu *vcpu, bool no_apf, gfn_t gfn, - gva_t gva, pfn_t *pfn) + gva_t gva, pfn_t *pfn, bool write, bool *writable) { bool async; - *pfn = gfn_to_pfn_async(vcpu->kvm, gfn, &async); + *pfn = gfn_to_pfn_async(vcpu->kvm, gfn, &async, write, writable); if (!async) return false; /* *pfn has correct page already */ @@ -2632,7 +2637,7 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, bool no_apf, gfn_t gfn, return true; } - *pfn = gfn_to_pfn(vcpu->kvm, gfn); + *pfn = gfn_to_pfn_prot(vcpu->kvm, gfn, write, writable); return false; } @@ -2645,6 +2650,8 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code, int level; gfn_t gfn = gpa >> PAGE_SHIFT; unsigned long mmu_seq; + int write = error_code & PFERR_WRITE_MASK; + bool map_writable; ASSERT(vcpu); ASSERT(VALID_PAGE(vcpu->arch.mmu.root_hpa)); @@ -2660,7 +2667,7 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code, mmu_seq = vcpu->kvm->mmu_notifier_seq; smp_rmb(); - if (try_async_pf(vcpu, no_apf, gfn, gpa, &pfn)) + if (try_async_pf(vcpu, no_apf, gfn, gpa, &pfn, write, &map_writable)) return 0; /* mmio */ @@ -2670,7 +2677,7 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code, if (mmu_notifier_retry(vcpu, mmu_seq)) goto out_unlock; kvm_mmu_free_some_pages(vcpu); - r = __direct_map(vcpu, gpa, error_code & PFERR_WRITE_MASK, + r = __direct_map(vcpu, gpa, write, map_writable, level, gfn, pfn); spin_unlock(&vcpu->kvm->mmu_lock); diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index d6b281e989b..ba00eefa7bc 100644 --- a/arch/x86/kvm/paging_tmpl.h +++ b/arch/x86/kvm/paging_tmpl.h @@ -427,7 +427,7 @@ static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu, struct guest_walker *gw, static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, struct guest_walker *gw, int user_fault, int write_fault, int hlevel, - int *ptwrite, pfn_t pfn) + int *ptwrite, pfn_t pfn, bool map_writable) { unsigned access = gw->pt_access; struct kvm_mmu_page *sp = NULL; @@ -501,7 +501,7 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, mmu_set_spte(vcpu, it.sptep, access, gw->pte_access & access, user_fault, write_fault, dirty, ptwrite, it.level, - gw->gfn, pfn, false, true); + gw->gfn, pfn, false, map_writable); FNAME(pte_prefetch)(vcpu, gw, it.sptep); return it.sptep; @@ -539,6 +539,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code, pfn_t pfn; int level = PT_PAGE_TABLE_LEVEL; unsigned long mmu_seq; + bool map_writable; pgprintk("%s: addr %lx err %x\n", __func__, addr, error_code); @@ -569,13 +570,17 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code, mmu_seq = vcpu->kvm->mmu_notifier_seq; smp_rmb(); - if (try_async_pf(vcpu, no_apf, walker.gfn, addr, &pfn)) + if (try_async_pf(vcpu, no_apf, walker.gfn, addr, &pfn, write_fault, + &map_writable)) return 0; /* mmio */ if (is_error_pfn(pfn)) return kvm_handle_bad_page(vcpu->kvm, walker.gfn, pfn); + if (!map_writable) + walker.pte_access &= ~ACC_WRITE_MASK; + spin_lock(&vcpu->kvm->mmu_lock); if (mmu_notifier_retry(vcpu, mmu_seq)) goto out_unlock; @@ -583,7 +588,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code, trace_kvm_mmu_audit(vcpu, AUDIT_PRE_PAGE_FAULT); kvm_mmu_free_some_pages(vcpu); sptep = FNAME(fetch)(vcpu, addr, &walker, user_fault, write_fault, - level, &write_pt, pfn); + level, &write_pt, pfn, map_writable); (void)sptep; pgprintk("%s: shadow pte %p %llx ptwrite %d\n", __func__, sptep, *sptep, write_pt); diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index ee4314e15ea..462b982fedf 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -334,8 +334,11 @@ void kvm_set_page_accessed(struct page *page); pfn_t hva_to_pfn_atomic(struct kvm *kvm, unsigned long addr); pfn_t gfn_to_pfn_atomic(struct kvm *kvm, gfn_t gfn); -pfn_t gfn_to_pfn_async(struct kvm *kvm, gfn_t gfn, bool *async); +pfn_t gfn_to_pfn_async(struct kvm *kvm, gfn_t gfn, bool *async, + bool write_fault, bool *writable); pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn); +pfn_t gfn_to_pfn_prot(struct kvm *kvm, gfn_t gfn, bool write_fault, + bool *writable); pfn_t gfn_to_pfn_memslot(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn); int memslot_id(struct kvm *kvm, gfn_t gfn); diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 475a100f3a2..2803b4db2a3 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -959,7 +959,7 @@ static pfn_t get_fault_pfn(void) } static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic, - bool *async) + bool *async, bool write_fault, bool *writable) { struct page *page[1]; int npages = 0; @@ -968,12 +968,34 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic, /* we can do it either atomically or asynchronously, not both */ BUG_ON(atomic && async); + BUG_ON(!write_fault && !writable); + + if (writable) + *writable = true; + if (atomic || async) npages = __get_user_pages_fast(addr, 1, 1, page); if (unlikely(npages != 1) && !atomic) { might_sleep(); - npages = get_user_pages_fast(addr, 1, 1, page); + + if (writable) + *writable = write_fault; + + npages = get_user_pages_fast(addr, 1, write_fault, page); + + /* map read fault as writable if possible */ + if (unlikely(!write_fault) && npages == 1) { + struct page *wpage[1]; + + npages = __get_user_pages_fast(addr, 1, 1, wpage); + if (npages == 1) { + *writable = true; + put_page(page[0]); + page[0] = wpage[0]; + } + npages = 1; + } } if (unlikely(npages != 1)) { @@ -1011,11 +1033,12 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic, pfn_t hva_to_pfn_atomic(struct kvm *kvm, unsigned long addr) { - return hva_to_pfn(kvm, addr, true, NULL); + return hva_to_pfn(kvm, addr, true, NULL, true, NULL); } EXPORT_SYMBOL_GPL(hva_to_pfn_atomic); -static pfn_t __gfn_to_pfn(struct kvm *kvm, gfn_t gfn, bool atomic, bool *async) +static pfn_t __gfn_to_pfn(struct kvm *kvm, gfn_t gfn, bool atomic, bool *async, + bool write_fault, bool *writable) { unsigned long addr; @@ -1028,32 +1051,40 @@ static pfn_t __gfn_to_pfn(struct kvm *kvm, gfn_t gfn, bool atomic, bool *async) return page_to_pfn(bad_page); } - return hva_to_pfn(kvm, addr, atomic, async); + return hva_to_pfn(kvm, addr, atomic, async, write_fault, writable); } pfn_t gfn_to_pfn_atomic(struct kvm *kvm, gfn_t gfn) { - return __gfn_to_pfn(kvm, gfn, true, NULL); + return __gfn_to_pfn(kvm, gfn, true, NULL, true, NULL); } EXPORT_SYMBOL_GPL(gfn_to_pfn_atomic); -pfn_t gfn_to_pfn_async(struct kvm *kvm, gfn_t gfn, bool *async) +pfn_t gfn_to_pfn_async(struct kvm *kvm, gfn_t gfn, bool *async, + bool write_fault, bool *writable) { - return __gfn_to_pfn(kvm, gfn, false, async); + return __gfn_to_pfn(kvm, gfn, false, async, write_fault, writable); } EXPORT_SYMBOL_GPL(gfn_to_pfn_async); pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn) { - return __gfn_to_pfn(kvm, gfn, false, NULL); + return __gfn_to_pfn(kvm, gfn, false, NULL, true, NULL); } EXPORT_SYMBOL_GPL(gfn_to_pfn); +pfn_t gfn_to_pfn_prot(struct kvm *kvm, gfn_t gfn, bool write_fault, + bool *writable) +{ + return __gfn_to_pfn(kvm, gfn, false, NULL, write_fault, writable); +} +EXPORT_SYMBOL_GPL(gfn_to_pfn_prot); + pfn_t gfn_to_pfn_memslot(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn) { unsigned long addr = gfn_to_hva_memslot(slot, gfn); - return hva_to_pfn(kvm, addr, false, NULL); + return hva_to_pfn(kvm, addr, false, NULL, true, NULL); } int gfn_to_page_many_atomic(struct kvm *kvm, gfn_t gfn, struct page **pages, -- 2.20.1