Re: [PATCH 2/2] KVM: selftests: arm64: Add 52-bit VA guest modes

[Itaru Kitayama <itaru.kitayama@fujitsu.com>]

Hi Fuad,
On Fri, Sep 04, 2026 at 09:45:30AM +0100, Fuad Tabba wrote:
> Hi Itaru,
> 
> On Tue, 25 Aug 2026 at 22:18, Itaru Kitayama <itaru.kitayama@fujitsu.com> wrote:
> ...
> > diff --git a/tools/testing/selftests/kvm/lib/arm64/processor.c b/tools/testing/selftests/kvm/lib/arm64/processor.c
> > index 9108e14a9b5b..bcdf670c9eb8 100644
> > --- a/tools/testing/selftests/kvm/lib/arm64/processor.c
> > +++ b/tools/testing/selftests/kvm/lib/arm64/processor.c
> > @@ -46,7 +46,7 @@ static u64 pud_index(struct kvm_vm *vm, gva_t gva)
> >         u64 mask = (1UL << (vm->page_shift - 3)) - 1;
> >
> >         TEST_ASSERT(vm->mmu.pgtable_levels >= 4,
> > -                   "Mode %d does not have at least 4 page table levels",
> > +                   "Mode %d does not have >= 4 page table levels",
> 
> Patch 1 added this string one commit earlier. Could it go in with the
> final wording there?

Surely, will fix in v2.

> 
> ...
> 
> > @@ -298,10 +304,14 @@ struct kvm_vm *____vm_create(struct vm_shape shape)
> >
> >         /* Setup mode specific traits. */
> >         switch (vm->mode) {
> > +       case VM_MODE_P52V52_4K:
> > +               vm->mmu.pgtable_levels = 5;
> > +               break;
> 
> This is now the deepest mode, so page_fault_test.c's sizing is stale:
> 
>    * VM_MODE_P48V48_4K is the mode with most PT pages; let's use
>    * twice that just in case.
>   pt_size = 26 * guest_page_size;
> 
> The margin still covers it. Could pt_size come from vm->mmu.pgtable_levels?

I'm not the author of the page_fault_test.c for arm64, but so I'm
guessing here; per the comment in the test, I dont think total number of
levels determines pt_size, rather by the addresses prepared for the
test.

This stress test does not require high virtual addresses, though should
we update the comment while at it?

Thanks,
Itaru.

> 
> Cheers,
> /fuad
> 
> 
> >         case VM_MODE_P52V48_4K:
> >                 vm->mmu.pgtable_levels = 4;
> >                 break;
> >         case VM_MODE_P52V48_64K:
> > +       case VM_MODE_P52V52_64K:
> >                 vm->mmu.pgtable_levels = 3;
> >                 break;
> >         case VM_MODE_P48V48_4K:
> > @@ -322,6 +332,7 @@ struct kvm_vm *____vm_create(struct vm_shape shape)
> >         case VM_MODE_P48V48_16K:
> >         case VM_MODE_P40V48_16K:
> >         case VM_MODE_P36V48_16K:
> > +       case VM_MODE_P52V52_16K:
> >                 vm->mmu.pgtable_levels = 4;
> >                 break;
> >         case VM_MODE_P47V47_16K:
> >
> > --
> > 2.43.0
> >
>