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Subject[PATCH 33/40] KVM: x86: switch kvm_set_memory_alias to SRCU update
Date
From: Marcelo Tosatti <mtosatti@redhat.com>

Using a similar two-step procedure as for memslots.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
---
arch/x86/include/asm/kvm_host.h | 4 ++
arch/x86/kvm/x86.c | 60 +++++++++++++++++++++++++++++++++------
include/linux/kvm_host.h | 6 ++++
virt/kvm/kvm_main.c | 4 +-
4 files changed, 63 insertions(+), 11 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 7cdcb3d..6c8c7c5 100644
--- 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 2d7c040..59f4da4 100644
--- 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
@@ -2224,11 +2225,32 @@ 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];
@@ -2249,7 +2271,7 @@ 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 */
@@ -2266,28 +2288,48 @@ 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
--- 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
--- 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();
--
1.6.5.3


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