RE: [PATCH] selftests: kvm: Fix a potential elf loading issue

[Duan, Zhenzhong]

> -----Original Message-----
> From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Sent: Monday, May 24, 2021 8:28 PM
> To: Duan, Zhenzhong <zhenzhong.duan@xxxxxxxxx>; linux-
> kernel@xxxxxxxxxxxxxxx
> Cc: linux-kselftest@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; shuah@xxxxxxxxxx
> Subject: Re: [PATCH] selftests: kvm: Fix a potential elf loading issue
> 
> On 12/05/21 06:31, Zhenzhong Duan wrote:
> > vm_vaddr_alloc() setup GVA to GPA mapping page by page, then GPA may
> > not be continuous if same memslot is used for data and page table
> allocation.
> >
> > kvm_vm_elf_load() expects a continuous memory of GPA or else it need
> > to read file data page by page. Fix it by adding a check in
> > vm_vaddr_alloc() to ensure memory is allocated in a whole if same
> > memslot is used for data and page table.
> >
> > Signed-off-by: Zhenzhong Duan <zhenzhong.duan@xxxxxxxxx>
> > ---
> Why not do
> 
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c
> b/tools/testing/selftests/kvm/lib/kvm_util.c
> index 7426163d448a..f362a066f37a 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -1170,6 +1170,9 @@ vm_vaddr_t vm_vaddr_alloc(struct kvm_vm *vm,
> size_t sz, vm_vaddr_t vaddr_min,
>   	uint64_t pages = (sz >> vm->page_shift) + ((sz % vm->page_size) != 0);
> 
>   	virt_pgd_alloc(vm, pgd_memslot);
> +	vm_paddr_t paddr = vm_phy_pages_alloc(vm, pages,
> +					      KVM_UTIL_MIN_PFN * vm-
> >page_size,
> +					      data_memslot);
> 
>   	/*
>   	 * Find an unused range of virtual page addresses of at least @@ -
> 1179,11 +1182,7 @@ vm_vaddr_t vm_vaddr_alloc(struct kvm_vm *vm,
> size_t sz, vm_vaddr_t vaddr_min,
> 
>   	/* Map the virtual pages. */
>   	for (vm_vaddr_t vaddr = vaddr_start; pages > 0;
> -		pages--, vaddr += vm->page_size) {
> -		vm_paddr_t paddr;
> -
> -		paddr = vm_phy_page_alloc(vm,
> -				KVM_UTIL_MIN_PFN * vm->page_size,
> data_memslot);
> +		pages--, vaddr += vm->page_size, paddr += vm->page_size) {
> 
>   		virt_pg_map(vm, vaddr, paddr, pgd_memslot);
> 
> 
> instead?

Yes, this is better, thanks for fixing.

Regards
Zhenzhong