On 23/06/2018 01:35, Liran Alon wrote:
> + for_each_clear_bit(bit, vmcs12_bitmap + offset,
> + nested_vmcs_fields_per_group(vmx)) {
You cannot be sure that nested_vmcs_fields_per_group(vmx) <= 64; the
index spans bits 1 to 9, so it can be at most 1024. In fact, even hough
it is currently the case that it is less than 64, this code already
breaks on 32-bit machines since guest interruptibility state is
00004824H for example.
Here I think it's much better if we already do the optimization you
mention in the cover letter, of computing vmcs_field_to_offset(field) >=
0 && cpu_has_vmcs_field(field) at startup. Then this loop becomes just
a word-by-word AND of vmcs12_bitmap with the bitmap you computed at
startup; really just a single AND on 64-bit machines and two for 32-bits.
Thanks,
Paolo
> + unsigned long field = base + bit;
> +
> + if (vmcs_field_to_offset(field) >= 0 &&
> + cpu_has_vmcs_field(field))
> + val &= ~(1ul << bit);
> + }
> +
> + vmcs02_bitmap[offset] = val;
