Commit c23e2b71 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

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



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: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarIsaku Yamahata <isaku.yamahata@intel.com>
Message-Id: <5919f685f109a1b0ebc6bd8fc4536ee94bcc172d.1705965635.git.isaku.yamahata@intel.com>
Reviewed-by: default avatarXiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: default avatarBinbin Wu <binbin.wu@linux.intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent a96cb3bf

include/linux/kvm_types.h

+1 −0
Original line number Diff line number Diff line
@@ -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;

virt/kvm/kvm_main.c

+14 −2
Original line number Diff line number Diff line
@@ -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;