| Message ID | 20200622200822.4426-6-sean.j.christopherson@intel.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | KVM: Cleanup and unify kvm_mmu_memory_cache usage | expand |
On Mon, Jun 22, 2020 at 1:09 PM Sean Christopherson <sean.j.christopherson@intel.com> wrote: > > Attempt to allocate a new object instead of crashing KVM (and likely the > kernel) if a memory cache is unexpectedly empty. Use GFP_ATOMIC for the > allocation as the caches are used while holding mmu_lock. The immediate > BUG_ON() makes the code unnecessarily explosive and led to confusing > minimums being used in the past, e.g. allocating 4 objects where 1 would > suffice. > Reviewed-by: Ben Gardon <bgardon@google.com> > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> > --- > arch/x86/kvm/mmu/mmu.c | 21 +++++++++++++++------ > 1 file changed, 15 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index ba70de24a5b0..5e773564ab20 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -1060,6 +1060,15 @@ static void walk_shadow_page_lockless_end(struct kvm_vcpu *vcpu) > local_irq_enable(); > } > > +static inline void *mmu_memory_cache_alloc_obj(struct kvm_mmu_memory_cache *mc, > + gfp_t gfp_flags) > +{ > + if (mc->kmem_cache) > + return kmem_cache_zalloc(mc->kmem_cache, gfp_flags); > + else > + return (void *)__get_free_page(gfp_flags); > +} > + > static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int min) > { > void *obj; > @@ -1067,10 +1076,7 @@ static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int min) > if (mc->nobjs >= min) > return 0; > while (mc->nobjs < ARRAY_SIZE(mc->objects)) { > - if (mc->kmem_cache) > - obj = kmem_cache_zalloc(mc->kmem_cache, GFP_KERNEL_ACCOUNT); > - else > - obj = (void *)__get_free_page(GFP_KERNEL_ACCOUNT); > + obj = mmu_memory_cache_alloc_obj(mc, GFP_KERNEL_ACCOUNT); > if (!obj) > return mc->nobjs >= min ? 0 : -ENOMEM; > mc->objects[mc->nobjs++] = obj; > @@ -1118,8 +1124,11 @@ static void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc) > { > void *p; > > - BUG_ON(!mc->nobjs); > - p = mc->objects[--mc->nobjs]; > + if (WARN_ON(!mc->nobjs)) > + p = mmu_memory_cache_alloc_obj(mc, GFP_ATOMIC | __GFP_ACCOUNT); > + else > + p = mc->objects[--mc->nobjs]; > + BUG_ON(!p); > return p; > } > > -- > 2.26.0 >
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index ba70de24a5b0..5e773564ab20 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -1060,6 +1060,15 @@ static void walk_shadow_page_lockless_end(struct kvm_vcpu *vcpu) local_irq_enable(); } +static inline void *mmu_memory_cache_alloc_obj(struct kvm_mmu_memory_cache *mc, + gfp_t gfp_flags) +{ + if (mc->kmem_cache) + return kmem_cache_zalloc(mc->kmem_cache, gfp_flags); + else + return (void *)__get_free_page(gfp_flags); +} + static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int min) { void *obj; @@ -1067,10 +1076,7 @@ static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int min) if (mc->nobjs >= min) return 0; while (mc->nobjs < ARRAY_SIZE(mc->objects)) { - if (mc->kmem_cache) - obj = kmem_cache_zalloc(mc->kmem_cache, GFP_KERNEL_ACCOUNT); - else - obj = (void *)__get_free_page(GFP_KERNEL_ACCOUNT); + obj = mmu_memory_cache_alloc_obj(mc, GFP_KERNEL_ACCOUNT); if (!obj) return mc->nobjs >= min ? 0 : -ENOMEM; mc->objects[mc->nobjs++] = obj; @@ -1118,8 +1124,11 @@ static void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc) { void *p; - BUG_ON(!mc->nobjs); - p = mc->objects[--mc->nobjs]; + if (WARN_ON(!mc->nobjs)) + p = mmu_memory_cache_alloc_obj(mc, GFP_ATOMIC | __GFP_ACCOUNT); + else + p = mc->objects[--mc->nobjs]; + BUG_ON(!p); return p; }
Attempt to allocate a new object instead of crashing KVM (and likely the kernel) if a memory cache is unexpectedly empty. Use GFP_ATOMIC for the allocation as the caches are used while holding mmu_lock. The immediate BUG_ON() makes the code unnecessarily explosive and led to confusing minimums being used in the past, e.g. allocating 4 objects where 1 would suffice. Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> --- arch/x86/kvm/mmu/mmu.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-)