* [PATCH 02/10] KVM: PPC: Book3S HV: radix clear pte when unmapping
@ 2018-05-06 7:37 Nicholas Piggin
2018-05-07 0:32 ` Paul Mackerras
2018-05-07 2:41 ` Nicholas Piggin
0 siblings, 2 replies; 3+ messages in thread
From: Nicholas Piggin @ 2018-05-06 7:37 UTC (permalink / raw)
To: kvm-ppc
The current partition table unmap code clears the _PAGE_PRESENT bit
out of the pte, which leaves pud_huge/pmd_huge true and does not
clear pud_present/pmd_present. This can confuse subsequent page
faults.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
arch/powerpc/kvm/book3s_64_mmu_radix.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c
index a6870288c0e0..361f42c8c73e 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_radix.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c
@@ -584,7 +584,7 @@ int kvm_unmap_radix(struct kvm *kvm, struct kvm_memory_slot *memslot,
ptep = __find_linux_pte(kvm->arch.pgtable, gpa, NULL, &shift);
if (ptep && pte_present(*ptep)) {
- old = kvmppc_radix_update_pte(kvm, ptep, _PAGE_PRESENT, 0,
+ old = kvmppc_radix_update_pte(kvm, ptep, ~0UL, 0,
gpa, shift);
kvmppc_radix_tlbie_page(kvm, gpa, shift);
if ((old & _PAGE_DIRTY) && memslot->dirty_bitmap) {
--
2.17.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH 02/10] KVM: PPC: Book3S HV: radix clear pte when unmapping
2018-05-06 7:37 [PATCH 02/10] KVM: PPC: Book3S HV: radix clear pte when unmapping Nicholas Piggin
@ 2018-05-07 0:32 ` Paul Mackerras
2018-05-07 2:41 ` Nicholas Piggin
1 sibling, 0 replies; 3+ messages in thread
From: Paul Mackerras @ 2018-05-07 0:32 UTC (permalink / raw)
To: kvm-ppc
On Sun, May 06, 2018 at 05:37:23PM +1000, Nicholas Piggin wrote:
> The current partition table unmap code clears the _PAGE_PRESENT bit
> out of the pte, which leaves pud_huge/pmd_huge true and does not
> clear pud_present/pmd_present. This can confuse subsequent page
> faults.
I'm OK with the patch, but this sounds like we can have a pmd where
the hardware does not consider it to be a valid translation, but
pmd_huge() and pmd_present() are both true. That sounds like a
disaster waiting to happen elsewhere -- pmd_present() at least should
be fixed, and possible pmd_huge() also.
Paul.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH 02/10] KVM: PPC: Book3S HV: radix clear pte when unmapping
2018-05-06 7:37 [PATCH 02/10] KVM: PPC: Book3S HV: radix clear pte when unmapping Nicholas Piggin
2018-05-07 0:32 ` Paul Mackerras
@ 2018-05-07 2:41 ` Nicholas Piggin
1 sibling, 0 replies; 3+ messages in thread
From: Nicholas Piggin @ 2018-05-07 2:41 UTC (permalink / raw)
To: kvm-ppc
On Mon, 7 May 2018 10:32:52 +1000
Paul Mackerras <paulus@ozlabs.org> wrote:
> On Sun, May 06, 2018 at 05:37:23PM +1000, Nicholas Piggin wrote:
> > The current partition table unmap code clears the _PAGE_PRESENT bit
> > out of the pte, which leaves pud_huge/pmd_huge true and does not
> > clear pud_present/pmd_present. This can confuse subsequent page
> > faults.
>
> I'm OK with the patch, but this sounds like we can have a pmd where
> the hardware does not consider it to be a valid translation, but
> pmd_huge() and pmd_present() are both true. That sounds like a
> disaster waiting to happen elsewhere -- pmd_present() at least should
> be fixed, and possible pmd_huge() also.
I don't know that we can after this patch. I can't see where that
would happen.
If you mean you just want to test just PAGE_PRESENT just in case
there are similar bugs, then sure I don't see a problem with that.
Thanks,
Nick
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2018-05-07 2:41 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2018-05-06 7:37 [PATCH 02/10] KVM: PPC: Book3S HV: radix clear pte when unmapping Nicholas Piggin
2018-05-07 0:32 ` Paul Mackerras
2018-05-07 2:41 ` Nicholas Piggin
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