From e930bffe95e1e886a1ede80726ea38df5838d067 Mon Sep 17 00:00:00 2001 From: Andrea Arcangeli Date: Fri, 25 Jul 2008 16:24:52 +0200 Subject: KVM: Synchronize guest physical memory map to host virtual memory map Synchronize changes to host virtual addresses which are part of a KVM memory slot to the KVM shadow mmu. This allows pte operations like swapping, page migration, and madvise() to transparently work with KVM. Signed-off-by: Andrea Arcangeli Signed-off-by: Avi Kivity --- arch/x86/kvm/mmu.c | 100 +++++++++++++++++++++++++++++++++ arch/x86/kvm/paging_tmpl.h | 12 ++++ include/asm-x86/kvm_host.h | 6 ++ include/linux/kvm_host.h | 24 ++++++++ virt/kvm/kvm_main.c | 135 +++++++++++++++++++++++++++++++++++++++++++++ 5 files changed, 277 insertions(+) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 2fa231923cf7..0bfe2bd305eb 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -653,6 +653,84 @@ static void rmap_write_protect(struct kvm *kvm, u64 gfn) account_shadowed(kvm, gfn); } +static int kvm_unmap_rmapp(struct kvm *kvm, unsigned long *rmapp) +{ + u64 *spte; + int need_tlb_flush = 0; + + while ((spte = rmap_next(kvm, rmapp, NULL))) { + BUG_ON(!(*spte & PT_PRESENT_MASK)); + rmap_printk("kvm_rmap_unmap_hva: spte %p %llx\n", spte, *spte); + rmap_remove(kvm, spte); + set_shadow_pte(spte, shadow_trap_nonpresent_pte); + need_tlb_flush = 1; + } + return need_tlb_flush; +} + +static int kvm_handle_hva(struct kvm *kvm, unsigned long hva, + int (*handler)(struct kvm *kvm, unsigned long *rmapp)) +{ + int i; + int retval = 0; + + /* + * If mmap_sem isn't taken, we can look the memslots with only + * the mmu_lock by skipping over the slots with userspace_addr == 0. + */ + for (i = 0; i < kvm->nmemslots; i++) { + struct kvm_memory_slot *memslot = &kvm->memslots[i]; + unsigned long start = memslot->userspace_addr; + unsigned long end; + + /* mmu_lock protects userspace_addr */ + if (!start) + continue; + + end = start + (memslot->npages << PAGE_SHIFT); + if (hva >= start && hva < end) { + gfn_t gfn_offset = (hva - start) >> PAGE_SHIFT; + retval |= handler(kvm, &memslot->rmap[gfn_offset]); + retval |= handler(kvm, + &memslot->lpage_info[ + gfn_offset / + KVM_PAGES_PER_HPAGE].rmap_pde); + } + } + + return retval; +} + +int kvm_unmap_hva(struct kvm *kvm, unsigned long hva) +{ + return kvm_handle_hva(kvm, hva, kvm_unmap_rmapp); +} + +static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp) +{ + u64 *spte; + int young = 0; + + spte = rmap_next(kvm, rmapp, NULL); + while (spte) { + int _young; + u64 _spte = *spte; + BUG_ON(!(_spte & PT_PRESENT_MASK)); + _young = _spte & PT_ACCESSED_MASK; + if (_young) { + young = 1; + clear_bit(PT_ACCESSED_SHIFT, (unsigned long *)spte); + } + spte = rmap_next(kvm, rmapp, spte); + } + return young; +} + +int kvm_age_hva(struct kvm *kvm, unsigned long hva) +{ + return kvm_handle_hva(kvm, hva, kvm_age_rmapp); +} + #ifdef MMU_DEBUG static int is_empty_shadow_page(u64 *spt) { @@ -1203,6 +1281,7 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn) int r; int largepage = 0; pfn_t pfn; + unsigned long mmu_seq; down_read(¤t->mm->mmap_sem); if (is_largepage_backed(vcpu, gfn & ~(KVM_PAGES_PER_HPAGE-1))) { @@ -1210,6 +1289,8 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn) largepage = 1; } + mmu_seq = vcpu->kvm->mmu_notifier_seq; + /* implicit mb(), we'll read before PT lock is unlocked */ pfn = gfn_to_pfn(vcpu->kvm, gfn); up_read(¤t->mm->mmap_sem); @@ -1220,6 +1301,8 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn) } spin_lock(&vcpu->kvm->mmu_lock); + if (mmu_notifier_retry(vcpu, mmu_seq)) + goto out_unlock; kvm_mmu_free_some_pages(vcpu); r = __direct_map(vcpu, v, write, largepage, gfn, pfn, PT32E_ROOT_LEVEL); @@ -1227,6 +1310,11 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, int write, gfn_t gfn) return r; + +out_unlock: + spin_unlock(&vcpu->kvm->mmu_lock); + kvm_release_pfn_clean(pfn); + return 0; } @@ -1345,6 +1433,7 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, int r; int largepage = 0; gfn_t gfn = gpa >> PAGE_SHIFT; + unsigned long mmu_seq; ASSERT(vcpu); ASSERT(VALID_PAGE(vcpu->arch.mmu.root_hpa)); @@ -1358,6 +1447,8 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, gfn &= ~(KVM_PAGES_PER_HPAGE-1); largepage = 1; } + mmu_seq = vcpu->kvm->mmu_notifier_seq; + /* implicit mb(), we'll read before PT lock is unlocked */ pfn = gfn_to_pfn(vcpu->kvm, gfn); up_read(¤t->mm->mmap_sem); if (is_error_pfn(pfn)) { @@ -1365,12 +1456,19 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, return 1; } spin_lock(&vcpu->kvm->mmu_lock); + 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, largepage, gfn, pfn, kvm_x86_ops->get_tdp_level()); spin_unlock(&vcpu->kvm->mmu_lock); return r; + +out_unlock: + spin_unlock(&vcpu->kvm->mmu_lock); + kvm_release_pfn_clean(pfn); + return 0; } static void nonpaging_free(struct kvm_vcpu *vcpu) @@ -1670,6 +1768,8 @@ static void mmu_guess_page_from_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa, gfn &= ~(KVM_PAGES_PER_HPAGE-1); vcpu->arch.update_pte.largepage = 1; } + vcpu->arch.update_pte.mmu_seq = vcpu->kvm->mmu_notifier_seq; + /* implicit mb(), we'll read before PT lock is unlocked */ pfn = gfn_to_pfn(vcpu->kvm, gfn); up_read(¤t->mm->mmap_sem); diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index 4d918220baeb..f72ac1fa35f0 100644 --- a/arch/x86/kvm/paging_tmpl.h +++ b/arch/x86/kvm/paging_tmpl.h @@ -263,6 +263,8 @@ static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *page, pfn = vcpu->arch.update_pte.pfn; if (is_error_pfn(pfn)) return; + if (mmu_notifier_retry(vcpu, vcpu->arch.update_pte.mmu_seq)) + return; kvm_get_pfn(pfn); mmu_set_spte(vcpu, spte, page->role.access, pte_access, 0, 0, gpte & PT_DIRTY_MASK, NULL, largepage, gpte_to_gfn(gpte), @@ -380,6 +382,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, int r; pfn_t pfn; int largepage = 0; + unsigned long mmu_seq; pgprintk("%s: addr %lx err %x\n", __func__, addr, error_code); kvm_mmu_audit(vcpu, "pre page fault"); @@ -413,6 +416,8 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, largepage = 1; } } + mmu_seq = vcpu->kvm->mmu_notifier_seq; + /* implicit mb(), we'll read before PT lock is unlocked */ pfn = gfn_to_pfn(vcpu->kvm, walker.gfn); up_read(¤t->mm->mmap_sem); @@ -424,6 +429,8 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, } spin_lock(&vcpu->kvm->mmu_lock); + if (mmu_notifier_retry(vcpu, mmu_seq)) + goto out_unlock; kvm_mmu_free_some_pages(vcpu); shadow_pte = FNAME(fetch)(vcpu, addr, &walker, user_fault, write_fault, largepage, &write_pt, pfn); @@ -439,6 +446,11 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, spin_unlock(&vcpu->kvm->mmu_lock); return write_pt; + +out_unlock: + spin_unlock(&vcpu->kvm->mmu_lock); + kvm_release_pfn_clean(pfn); + return 0; } static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t vaddr) diff --git a/include/asm-x86/kvm_host.h b/include/asm-x86/kvm_host.h index bc34dc21f178..0f3c53114614 100644 --- a/include/asm-x86/kvm_host.h +++ b/include/asm-x86/kvm_host.h @@ -13,6 +13,7 @@ #include #include +#include #include #include @@ -251,6 +252,7 @@ struct kvm_vcpu_arch { gfn_t gfn; /* presumed gfn during guest pte update */ pfn_t pfn; /* pfn corresponding to that gfn */ int largepage; + unsigned long mmu_seq; } update_pte; struct i387_fxsave_struct host_fx_image; @@ -729,4 +731,8 @@ asmlinkage void kvm_handle_fault_on_reboot(void); KVM_EX_ENTRY " 666b, 667b \n\t" \ ".popsection" +#define KVM_ARCH_WANT_MMU_NOTIFIER +int kvm_unmap_hva(struct kvm *kvm, unsigned long hva); +int kvm_age_hva(struct kvm *kvm, unsigned long hva); + #endif diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 07d68a8ae8e9..8525afc53107 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -121,6 +121,12 @@ struct kvm { struct kvm_coalesced_mmio_dev *coalesced_mmio_dev; struct kvm_coalesced_mmio_ring *coalesced_mmio_ring; #endif + +#ifdef KVM_ARCH_WANT_MMU_NOTIFIER + struct mmu_notifier mmu_notifier; + unsigned long mmu_notifier_seq; + long mmu_notifier_count; +#endif }; /* The guest did something we don't support. */ @@ -332,4 +338,22 @@ int kvm_trace_ioctl(unsigned int ioctl, unsigned long arg) #define kvm_trace_cleanup() ((void)0) #endif +#ifdef KVM_ARCH_WANT_MMU_NOTIFIER +static inline int mmu_notifier_retry(struct kvm_vcpu *vcpu, unsigned long mmu_seq) +{ + if (unlikely(vcpu->kvm->mmu_notifier_count)) + return 1; + /* + * Both reads happen under the mmu_lock and both values are + * modified under mmu_lock, so there's no need of smb_rmb() + * here in between, otherwise mmu_notifier_count should be + * read before mmu_notifier_seq, see + * mmu_notifier_invalidate_range_end write side. + */ + if (vcpu->kvm->mmu_notifier_seq != mmu_seq) + return 1; + return 0; +} +#endif + #endif diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 3735212cd3f8..7dd9b0b85e4e 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -192,6 +192,123 @@ void kvm_vcpu_uninit(struct kvm_vcpu *vcpu) } EXPORT_SYMBOL_GPL(kvm_vcpu_uninit); +#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER) +static inline struct kvm *mmu_notifier_to_kvm(struct mmu_notifier *mn) +{ + return container_of(mn, struct kvm, mmu_notifier); +} + +static void kvm_mmu_notifier_invalidate_page(struct mmu_notifier *mn, + struct mm_struct *mm, + unsigned long address) +{ + struct kvm *kvm = mmu_notifier_to_kvm(mn); + int need_tlb_flush; + + /* + * When ->invalidate_page runs, the linux pte has been zapped + * already but the page is still allocated until + * ->invalidate_page returns. So if we increase the sequence + * here the kvm page fault will notice if the spte can't be + * established because the page is going to be freed. If + * instead the kvm page fault establishes the spte before + * ->invalidate_page runs, kvm_unmap_hva will release it + * before returning. + * + * The sequence increase only need to be seen at spin_unlock + * time, and not at spin_lock time. + * + * Increasing the sequence after the spin_unlock would be + * unsafe because the kvm page fault could then establish the + * pte after kvm_unmap_hva returned, without noticing the page + * is going to be freed. + */ + spin_lock(&kvm->mmu_lock); + kvm->mmu_notifier_seq++; + need_tlb_flush = kvm_unmap_hva(kvm, address); + spin_unlock(&kvm->mmu_lock); + + /* we've to flush the tlb before the pages can be freed */ + if (need_tlb_flush) + kvm_flush_remote_tlbs(kvm); + +} + +static void kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn, + struct mm_struct *mm, + unsigned long start, + unsigned long end) +{ + struct kvm *kvm = mmu_notifier_to_kvm(mn); + int need_tlb_flush = 0; + + spin_lock(&kvm->mmu_lock); + /* + * The count increase must become visible at unlock time as no + * spte can be established without taking the mmu_lock and + * count is also read inside the mmu_lock critical section. + */ + kvm->mmu_notifier_count++; + for (; start < end; start += PAGE_SIZE) + need_tlb_flush |= kvm_unmap_hva(kvm, start); + spin_unlock(&kvm->mmu_lock); + + /* we've to flush the tlb before the pages can be freed */ + if (need_tlb_flush) + kvm_flush_remote_tlbs(kvm); +} + +static void kvm_mmu_notifier_invalidate_range_end(struct mmu_notifier *mn, + struct mm_struct *mm, + unsigned long start, + unsigned long end) +{ + struct kvm *kvm = mmu_notifier_to_kvm(mn); + + spin_lock(&kvm->mmu_lock); + /* + * This sequence increase will notify the kvm page fault that + * the page that is going to be mapped in the spte could have + * been freed. + */ + kvm->mmu_notifier_seq++; + /* + * The above sequence increase must be visible before the + * below count decrease but both values are read by the kvm + * page fault under mmu_lock spinlock so we don't need to add + * a smb_wmb() here in between the two. + */ + kvm->mmu_notifier_count--; + spin_unlock(&kvm->mmu_lock); + + BUG_ON(kvm->mmu_notifier_count < 0); +} + +static int kvm_mmu_notifier_clear_flush_young(struct mmu_notifier *mn, + struct mm_struct *mm, + unsigned long address) +{ + struct kvm *kvm = mmu_notifier_to_kvm(mn); + int young; + + spin_lock(&kvm->mmu_lock); + young = kvm_age_hva(kvm, address); + spin_unlock(&kvm->mmu_lock); + + if (young) + kvm_flush_remote_tlbs(kvm); + + return young; +} + +static const struct mmu_notifier_ops kvm_mmu_notifier_ops = { + .invalidate_page = kvm_mmu_notifier_invalidate_page, + .invalidate_range_start = kvm_mmu_notifier_invalidate_range_start, + .invalidate_range_end = kvm_mmu_notifier_invalidate_range_end, + .clear_flush_young = kvm_mmu_notifier_clear_flush_young, +}; +#endif /* CONFIG_MMU_NOTIFIER && KVM_ARCH_WANT_MMU_NOTIFIER */ + static struct kvm *kvm_create_vm(void) { struct kvm *kvm = kvm_arch_create_vm(); @@ -212,6 +329,21 @@ static struct kvm *kvm_create_vm(void) (struct kvm_coalesced_mmio_ring *)page_address(page); #endif +#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER) + { + int err; + kvm->mmu_notifier.ops = &kvm_mmu_notifier_ops; + err = mmu_notifier_register(&kvm->mmu_notifier, current->mm); + if (err) { +#ifdef KVM_COALESCED_MMIO_PAGE_OFFSET + put_page(page); +#endif + kfree(kvm); + return ERR_PTR(err); + } + } +#endif + kvm->mm = current->mm; atomic_inc(&kvm->mm->mm_count); spin_lock_init(&kvm->mmu_lock); @@ -271,6 +403,9 @@ static void kvm_destroy_vm(struct kvm *kvm) #ifdef KVM_COALESCED_MMIO_PAGE_OFFSET if (kvm->coalesced_mmio_ring != NULL) free_page((unsigned long)kvm->coalesced_mmio_ring); +#endif +#if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER) + mmu_notifier_unregister(&kvm->mmu_notifier, kvm->mm); #endif kvm_arch_destroy_vm(kvm); mmdrop(mm); -- cgit v1.2.1