Re: [PATCH 4/4] KVM: guest_memfd: Stop returning struct page from PFN lookup

[Ackerley Tng]

Yan Zhao <yan.y.zhao@xxxxxxxxx> writes:

> Hi Ackerley,
>
>> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
>> index 6c941aaa10c63..e5d637a5ec558 100644
>> --- a/arch/arm64/kvm/mmu.c
>> +++ b/arch/arm64/kvm/mmu.c
>> @@ -1613,7 +1613,7 @@ static int gmem_abort(const struct kvm_s2_fault_desc *s2fd)
>>  	enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R;
>>  	struct kvm_pgtable *pgt = s2fd->vcpu->arch.hw_mmu->pgt;
>>  	unsigned long mmu_seq;
>> -	struct page *page;
> Just drop the page should be ok, since
>> +	struct page *page = NULL;
>>  	struct kvm *kvm = s2fd->vcpu->kvm;
>>  	void *memcache = NULL;
>>  	kvm_pfn_t pfn;
>> @@ -1641,7 +1641,7 @@ static int gmem_abort(const struct kvm_s2_fault_desc *s2fd)
>>  	/* Pairs with the smp_wmb() in kvm_mmu_invalidate_end(). */
>>  	smp_rmb();
>>
>> -	ret = kvm_gmem_get_pfn(kvm, s2fd->memslot, gfn, &pfn, &page, NULL);
>> +	ret = kvm_gmem_get_pfn(kvm, s2fd->memslot, gfn, &pfn, NULL);
>>  	if (ret) {
>>  		kvm_prepare_memory_fault_exit(s2fd->vcpu, s2fd->fault_ipa, PAGE_SIZE,
>>  					      write_fault, exec_fault, false);
> here missed a hunk:
>  out_unlock:
> -       kvm_release_faultin_page(kvm, page, !!ret, prot & KVM_PGTABLE_PROT_W);
>         kvm_fault_unlock(kvm);
>
> I will fully test this series tomorrow.

Makes sense. gmem_abort() is purely gmem and there's non-gmem path to
fill the page pointer in, so the above is correct.

I'll not be respinning again today, sorry about the flurry of emails!