KVM: x86: switch kvm_set_memory_alias to SRCU update

Using a similar two-step procedure as for memslots.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 7cdcb3d..6c8c7c5 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -368,8 +368,12 @@ struct kvm_mem_alias {
        gfn_t base_gfn;
        unsigned long npages;
        gfn_t target_gfn;
+#define KVM_ALIAS_INVALID     1UL
+       unsigned long flags;
 };
 
+#define KVM_ARCH_HAS_UNALIAS_INSTANTIATION
+
 struct kvm_mem_aliases {
        struct kvm_mem_alias aliases[KVM_ALIAS_SLOTS];
        int naliases;

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e748835..28127c9 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -38,6 +38,7 @@
 #include <linux/intel-iommu.h>
 #include <linux/cpufreq.h>
 #include <linux/user-return-notifier.h>
+#include <linux/srcu.h>
 #include <trace/events/kvm.h>
 #undef TRACE_INCLUDE_FILE
 #define CREATE_TRACE_POINTS
@@ -2223,11 +2224,32 @@ static int kvm_vm_ioctl_get_nr_mmu_pages(struct kvm *kvm)
        return kvm->arch.n_alloc_mmu_pages;
 }
 
+gfn_t unalias_gfn_instantiation(struct kvm *kvm, gfn_t gfn)
+{
+       int i;
+       struct kvm_mem_alias *alias;
+       struct kvm_mem_aliases *aliases;
+
+       aliases = rcu_dereference(kvm->arch.aliases);
+
+       for (i = 0; i < aliases->naliases; ++i) {
+               alias = &aliases->aliases[i];
+               if (alias->flags & KVM_ALIAS_INVALID)
+                       continue;
+               if (gfn >= alias->base_gfn
+                   && gfn < alias->base_gfn + alias->npages)
+                       return alias->target_gfn + gfn - alias->base_gfn;
+       }
+       return gfn;
+}
+
 gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn)
 {
        int i;
        struct kvm_mem_alias *alias;
-       struct kvm_mem_aliases *aliases = kvm->arch.aliases;
+       struct kvm_mem_aliases *aliases;
+
+       aliases = rcu_dereference(kvm->arch.aliases);
 
        for (i = 0; i < aliases->naliases; ++i) {
                alias = &aliases->aliases[i];
@@ -2248,7 +2270,7 @@ static int kvm_vm_ioctl_set_memory_alias(struct kvm *kvm,
 {
        int r, n;
        struct kvm_mem_alias *p;
-       struct kvm_mem_aliases *aliases;
+       struct kvm_mem_aliases *aliases, *old_aliases;
 
        r = -EINVAL;
        /* General sanity checks */
@@ -2265,28 +2287,48 @@ static int kvm_vm_ioctl_set_memory_alias(struct kvm *kvm,
            < alias->target_phys_addr)
                goto out;
 
+       r = -ENOMEM;
+       aliases = kzalloc(sizeof(struct kvm_mem_aliases), GFP_KERNEL);
+       if (!aliases)
+               goto out;
+
        down_write(&kvm->slots_lock);
-       spin_lock(&kvm->mmu_lock);
 
-       aliases = kvm->arch.aliases;
+       /* invalidate any gfn reference in case of deletion/shrinking */
+       memcpy(aliases, kvm->arch.aliases, sizeof(struct kvm_mem_aliases));
+       aliases->aliases[alias->slot].flags |= KVM_ALIAS_INVALID;
+       old_aliases = kvm->arch.aliases;
+       rcu_assign_pointer(kvm->arch.aliases, aliases);
+       synchronize_srcu_expedited(&kvm->srcu);
+       kvm_mmu_zap_all(kvm);
+       kfree(old_aliases);
+
+       r = -ENOMEM;
+       aliases = kzalloc(sizeof(struct kvm_mem_aliases), GFP_KERNEL);
+       if (!aliases)
+               goto out_unlock;
+
+       memcpy(aliases, kvm->arch.aliases, sizeof(struct kvm_mem_aliases));
 
        p = &aliases->aliases[alias->slot];
        p->base_gfn = alias->guest_phys_addr >> PAGE_SHIFT;
        p->npages = alias->memory_size >> PAGE_SHIFT;
        p->target_gfn = alias->target_phys_addr >> PAGE_SHIFT;
+       p->flags &= ~(KVM_ALIAS_INVALID);
 
        for (n = KVM_ALIAS_SLOTS; n > 0; --n)
                if (aliases->aliases[n - 1].npages)
                        break;
        aliases->naliases = n;
 
-       spin_unlock(&kvm->mmu_lock);
-       kvm_mmu_zap_all(kvm);
+       old_aliases = kvm->arch.aliases;
+       rcu_assign_pointer(kvm->arch.aliases, aliases);
+       synchronize_srcu_expedited(&kvm->srcu);
+       kfree(old_aliases);
+       r = 0;
 
+out_unlock:
        up_write(&kvm->slots_lock);
-
-       return 0;
-
 out:
        return r;
 }

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 93bd307..20941c0 100644 (file)
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -266,6 +266,8 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
 void kvm_disable_largepages(void);
 void kvm_arch_flush_shadow(struct kvm *kvm);
 gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn);
+gfn_t unalias_gfn_instantiation(struct kvm *kvm, gfn_t gfn);
+
 struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn);
 unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn);
 void kvm_release_page_clean(struct page *page);
@@ -539,6 +541,10 @@ static inline int mmu_notifier_retry(struct kvm_vcpu *vcpu, unsigned long mmu_se
 }
 #endif
 
+#ifndef KVM_ARCH_HAS_UNALIAS_INSTANTIATION
+#define unalias_gfn_instantiation unalias_gfn
+#endif
+
 #ifdef CONFIG_HAVE_KVM_IRQCHIP
 
 #define KVM_MAX_IRQ_ROUTES 1024

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 2bb24a8..c680f7b 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -859,7 +859,7 @@ int kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn)
        int i;
        struct kvm_memslots *slots = rcu_dereference(kvm->memslots);
 
-       gfn = unalias_gfn(kvm, gfn);
+       gfn = unalias_gfn_instantiation(kvm, gfn);
        for (i = 0; i < KVM_MEMORY_SLOTS; ++i) {
                struct kvm_memory_slot *memslot = &slots->memslots[i];
 
@@ -896,7 +896,7 @@ unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
 {
        struct kvm_memory_slot *slot;
 
-       gfn = unalias_gfn(kvm, gfn);
+       gfn = unalias_gfn_instantiation(kvm, gfn);
        slot = gfn_to_memslot_unaliased(kvm, gfn);
        if (!slot || slot->flags & KVM_MEMSLOT_INVALID)
                return bad_hva();