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KVM: Allow page-sized MMU caches to be initialized with custom 64-bit values

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Add support to MMU caches for initializing a page with a custom 64-bit
value, e.g. to pre-fill an entire page table with non-zero PTE values.
The functionality will be used by x86 to support Intel's TDX, which needs
to set bit 63 in all non-present PTEs in order to prevent !PRESENT page
faults from getting reflected into the guest (Intel's EPT Violation #VE
architecture made the less than brilliant decision of having the per-PTE
behavior be opt-out instead of opt-in).

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Message-Id: <5919f685f109a1b0ebc6bd8fc4536ee94bcc172d.1705965635.git.isaku.yamahata@intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2024-01-22 15:53:11 -08:00 committed by Paolo Bonzini
parent a96cb3bf39
commit c23e2b7103
2 changed files with 15 additions and 2 deletions
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1
include/linux/kvm_types.h
View file

@ -86,6 +86,7 @@ struct gfn_to_pfn_cache {
struct kvm_mmu_memory_cache {
gfp_t gfp_zero;
gfp_t gfp_custom;
u64 init_value;
struct kmem_cache *kmem_cache;
int capacity;
int nobjs;

16
virt/kvm/kvm_main.c
View file

@ -401,12 +401,17 @@ static void kvm_flush_shadow_all(struct kvm *kvm)
static inline void *mmu_memory_cache_alloc_obj(struct kvm_mmu_memory_cache *mc,
gfp_t gfp_flags)
{
void *page;
gfp_flags |= mc->gfp_zero;
if (mc->kmem_cache)
return kmem_cache_alloc(mc->kmem_cache, gfp_flags);
else
return (void *)__get_free_page(gfp_flags);
page = (void *)__get_free_page(gfp_flags);
if (page && mc->init_value)
memset64(page, mc->init_value, PAGE_SIZE / sizeof(u64));
return page;
}
int __kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int capacity, int min)
@ -421,6 +426,13 @@ int __kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int capacity,
if (WARN_ON_ONCE(!capacity))
return -EIO;
/*
* Custom init values can be used only for page allocations,
* and obviously conflict with __GFP_ZERO.
*/
if (WARN_ON_ONCE(mc->init_value && (mc->kmem_cache || mc->gfp_zero)))
return -EIO;
mc->objects = kvmalloc_array(capacity, sizeof(void *), gfp);
if (!mc->objects)
return -ENOMEM;