On Thu, Feb 11, 2021 at 7:58 AM Sean Christopherson [off-list ref] wrote:

On Thu, Feb 11, 2021, Paolo Bonzini wrote:

quoted

On 11/02/21 02:56, Sean Christopherson wrote:

quoted

quoted

quoted

+       pta->gpa = (vm_get_max_gfn(vm) - guest_num_pages) * pta->guest_page_size;
+       pta->gpa &= ~(pta->host_page_size - 1);

Also not related to this patch, but another case for align.

quoted

         if (backing_src == VM_MEM_SRC_ANONYMOUS_THP ||
             backing_src == VM_MEM_SRC_ANONYMOUS_HUGETLB)
-               guest_test_phys_mem &= ~(KVM_UTIL_HUGEPAGE_ALIGNMENT - 1);
-
+               pta->gpa &= ~(KVM_UTIL_HUGEPAGE_ALIGNMENT - 1);

also align

quoted

  #ifdef __s390x__
         /* Align to 1M (segment size) */
-       guest_test_phys_mem &= ~((1 << 20) - 1);
+       pta->gpa &= ~((1 << 20) - 1);

And here again (oof)

Yep, I'll fix all these and the align() comment in v2.

This is not exactly align in fact; it is x & ~y rather than (x + y) & ~y.
Are you going to introduce a round-down macro or is it a bug?  (I am
lazy...).

Good question.  I, too, was lazy.  I didn't look at the guts of align() when I
moved it, and I didn't look closely at Ben's suggestion.  I'll take a closer
look today and make sure everything is doing what it's supposed to do.

Ooh, great point Paolo, that helper is indeed rounding up. My comment
in patch #2 was totally wrong. I forgot anyone would ever want to
round up. :/
My misunderstanding and the above use cases are probably good evidence
that it would be helpful to have both align_up and align_down helpers.