Re: [PATCH v1 2/2] KVM: selftests: arm64: Fix pte encode/decode for PA bits > 48

[Oliver Upton <oliver.upton@linux.dev>]

Hi Ryan,

Thanks for fixing this. Couple of nits:

On Tue, Feb 28, 2023 at 05:07:56PM +0000, Ryan Roberts wrote:
> The high bits [51:48] of a physical address should appear at [15:12] in
> a 64K pte, not at [51:48] as was previously being programmed. Fix this
> with new helper functions that do the conversion correctly. This also
> sets us up nicely for adding LPA2 encodings in future.
> 
> Fixes: 7a6629ef746d ("kvm: selftests: add virt mem support for aarch64")
> 
> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>

nit: no whitespace between footers.

> ---
>  .../selftests/kvm/lib/aarch64/processor.c     | 32 ++++++++++++++-----
>  1 file changed, 24 insertions(+), 8 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/lib/aarch64/processor.c b/tools/testing/selftests/kvm/lib/aarch64/processor.c
> index 5972a23b2765..13f28d96521c 100644
> --- a/tools/testing/selftests/kvm/lib/aarch64/processor.c
> +++ b/tools/testing/selftests/kvm/lib/aarch64/processor.c
> @@ -58,10 +58,27 @@ static uint64_t pte_index(struct kvm_vm *vm, vm_vaddr_t gva)
>  	return (gva >> vm->page_shift) & mask;
>  }
>  
> -static uint64_t pte_addr(struct kvm_vm *vm, uint64_t entry)
> +static uint64_t addr_pte(struct kvm_vm *vm, uint64_t pa, uint64_t attrs)
>  {
> -	uint64_t mask = ((1UL << (vm->va_bits - vm->page_shift)) - 1) << vm->page_shift;
> -	return entry & mask;
> +	uint64_t pte;
> +
> +	pte = pa & GENMASK(47, vm->page_shift);
> +	if (vm->page_shift == 16)
> +		pte |= (pa & GENMASK(51, 48)) >> (48 - 12);

nit: this is a bit of an odd transformation, of course courtesy of the
architecture. FIELD_GET() might make it a bit more readable:

		pte |= FIELD_GET(GENMASK(51, 48), pa) << 12;

-- 
Thanks,
Oliver