Commit f029f04d authored by Ackerley Tng's avatar Ackerley Tng Committed by Paolo Bonzini
Browse files

KVM: x86/mmu: Handle guest page faults for guest_memfd with shared memory 



Update the KVM MMU fault handler to service guest page faults
for memory slots backed by guest_memfd with mmap support. For such
slots, the MMU must always fault in pages directly from guest_memfd,
bypassing the host's userspace_addr.

This ensures that guest_memfd-backed memory is always handled through
the guest_memfd specific faulting path, regardless of whether it's for
private or non-private (shared) use cases.

Additionally, rename kvm_mmu_faultin_pfn_private() to
kvm_mmu_faultin_pfn_gmem(), as this function is now used to fault in
pages from guest_memfd for both private and non-private memory,
accommodating the new use cases.

Co-developed-by: default avatarDavid Hildenbrand <david@redhat.com>
Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Signed-off-by: default avatarAckerley Tng <ackerleytng@google.com>
Co-developed-by: default avatarFuad Tabba <tabba@google.com>
Signed-off-by: default avatarFuad Tabba <tabba@google.com>
[sean: drop the helper]
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Reviewed-by: default avatarXiaoyao Li <xiaoyao.li@intel.com>
Message-ID: <20250729225455.670324-17-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent b7d97f69

arch/x86/kvm/mmu/mmu.c

+4 −4
Original line number Diff line number Diff line
@@ -4561,7 +4561,7 @@ static void kvm_mmu_finish_page_fault(struct kvm_vcpu *vcpu, 
				 r == RET_PF_RETRY, fault->map_writable);

}



static int kvm_mmu_faultin_pfn_private(struct kvm_vcpu *vcpu,

static int kvm_mmu_faultin_pfn_gmem(struct kvm_vcpu *vcpu,

				    struct kvm_page_fault *fault)

{

	int max_order, r;
@@ -4589,8 +4589,8 @@ static int __kvm_mmu_faultin_pfn(struct kvm_vcpu *vcpu, 
{

	unsigned int foll = fault->write ? FOLL_WRITE : 0;



	if (fault->is_private)

		return kvm_mmu_faultin_pfn_private(vcpu, fault);

	if (fault->is_private || kvm_memslot_is_gmem_only(fault->slot))

		return kvm_mmu_faultin_pfn_gmem(vcpu, fault);



	foll |= FOLL_NOWAIT;

	fault->pfn = __kvm_faultin_pfn(fault->slot, fault->gfn, foll,