]> err.no Git - linux-2.6/commitdiff
KVM: Synchronize guest physical memory map to host virtual memory map
authorAndrea Arcangeli <andrea@qumranet.com>
Fri, 25 Jul 2008 14:24:52 +0000 (16:24 +0200)
committerAvi Kivity <avi@qumranet.com>
Tue, 29 Jul 2008 09:33:53 +0000 (12:33 +0300)
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 <andrea@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
arch/x86/kvm/mmu.c
arch/x86/kvm/paging_tmpl.h
include/asm-x86/kvm_host.h
include/linux/kvm_host.h
virt/kvm/kvm_main.c

index 2fa231923cf7e90d9e969478f22207ba0040cd57..0bfe2bd305eb286aee2890e2be95b397c462d74c 100644 (file)
@@ -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(&current->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(&current->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(&current->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(&current->mm->mmap_sem);
 
index 4d918220baebf128f3db1d825f2b23895f53c933..f72ac1fa35f0bfe07b74b43f2275c28402518c9e 100644 (file)
@@ -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(&current->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)
index bc34dc21f178a0381441f49a580e788df7d8d2cd..0f3c531146142df89075e4623c36377510c7489e 100644 (file)
@@ -13,6 +13,7 @@
 
 #include <linux/types.h>
 #include <linux/mm.h>
+#include <linux/mmu_notifier.h>
 
 #include <linux/kvm.h>
 #include <linux/kvm_para.h>
@@ -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
index 07d68a8ae8e950bc21bdb86b8900aea4ee68b46e..8525afc53107faaaa993fa6ebae6c2d703eb718c 100644 (file)
@@ -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
index 3735212cd3f807b7c7cb8b7b9135069f1cfe5935..7dd9b0b85e4eea1aafaff116e993e6392c9cc173 100644 (file)
@@ -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);