| Message ID | 20180506073731.13097-3-npiggin@gmail.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | assorted radix fixes and improvemets for page fault and invalidation | expand |
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. -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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 -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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) {
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(-)