Re: [PATCH] KVM: selftests: Fix nx_huge_pages_test on TDP-disabled hosts

[Paolo Bonzini <pbonzini@redhat.com>]

On 9/27/22 00:20, Sean Christopherson wrote:
> void __virt_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr,
> 		uint64_t nr_bytes, size_t page_size)
> {
> 	uint64_t nr_pages = DIV_ROUND_UP(nr_bytes, page_size);
> 
> 	TEST_ASSERT(vaddr + size > vaddr, "Vaddr overflow");
> 	TEST_ASSERT(paddr + size > paddr, "Paddr overflow");
> 
> 	while (npages--) {
> 		virt_pg_map(vm, vaddr, paddr);
> 		vaddr += page_size;
> 		paddr += page_size;
> 	}
> }
> 
> void virt_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr,
> 	      uint64_t nr_bytes)
> {
> 	__virt_map(vm, vaddr, paddr, nr_bytes, vm->page_size);
> }

I would just keep nr_pages in virt_map to begin with, for the sake of 
this patch.  Changing virt_map can be done later (and should be separate 
anyway).

>> -	virt_map(vm, HPAGE_GVA, HPAGE_GPA, HPAGE_SLOT_NPAGES);
>> +	/*
>> +	 * Use 2MiB virtual mappings so that KVM can map the region with huge
>> +	 * pages even if TDP is disabled.
>> +	 */
>> +	virt_map_2m(vm, HPAGE_GVA, HPAGE_GPA, HPAGE_SLOT_2MB_PAGES);
> 
> Hmm, what about probing TDP support and deliberately using 4KiB pages when TDP is
> enabled?  That would give a bit of bonus coverage by verifying that KVM creates
> huge pages irrespective of guest mapping level.

Nice idea indeed.

Paolo