On 06/29/2016 04:49 AM, Paolo Bonzini wrote:
On 28/06/2016 22:37, Bandan Das wrote:
Paolo Bonzini <pbonzini@xxxxxxxxxx> writes:
On 28/06/2016 19:33, Bandan Das wrote:
static int is_shadow_present_pte(u64 pte)
{
- return pte & PT_PRESENT_MASK && !is_mmio_spte(pte);
+ return pte & (PT_PRESENT_MASK | shadow_x_mask) &&
+ !is_mmio_spte(pte);
This should really be pte & 7 when using EPT. But this is okay as an
alternative to a new shadow_present_mask.
I could revive shadow_xonly_valid probably... Anyway, for now I will
add a TODO comment here.
It's okay to it like this, because the only invalid PTEs reaching this
point are those that is_mmio_spte filters away. Hence you'll never get
-W- PTEs here, and pte & 7 is really the same as how you wrote it. It's
pretty clever, and doesn't need a TODO at all. :)
Thanks, understood. So, the way it is written now covers all cases for
pte & 7. Let's still add a comment - clever things are usually
confusing to many!
I think another way to write it is "(pte & 0xFFFFFFFFull) &&
!is_mmio_spte(pte)", since non-present/non-MMIO SPTEs never use bits
1..31 (they can have non-zero bits 32..63 on 32-bit CPUs where we don't
update the PTEs atomically). Guangrong, what do you prefer?
I think the way you innovated is better. :)
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