Messages in this thread Patch in this message | | | From | Linus Torvalds <> | Date | Fri, 17 Aug 2018 09:13:51 -0700 | Subject | Re: [PATCH] x86/speculation/l1tf: Exempt zeroed PTEs from XOR conversion |
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On Thu, Aug 16, 2018 at 1:47 PM Sean Christopherson <sean.j.christopherson@intel.com> wrote: > > Fixes: 6b28baca9b1f ("x86/speculation/l1tf: Protect PROT_NONE PTEs against speculation")
This seems wrong.
That commit doesn't invert a cleared page table entry, because that commit still required _PAGE_PROTNONE being set for a pte to be inverted.
I'm assuming the real culprit is commit f22cc87f6c1f ("x86/speculation/l1tf: Invert all not present mappings") which made it look at _just_ the present bit.
And yeah, that was wrong.
So I really think a much better patch would be the appended one-liner.
Note - it's whitespace-damaged by cut-and-paste, but it should be obvious enough to apply by hand.
Can you test this one instead?
Linus ---
arch/x86/include/asm/pgtable-invert.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/pgtable-invert.h b/arch/x86/include/asm/pgtable-invert.h index 44b1203ece12..821438e91b77 100644 --- a/arch/x86/include/asm/pgtable-invert.h +++ b/arch/x86/include/asm/pgtable-invert.h @@ -6,7 +6,7 @@
static inline bool __pte_needs_invert(u64 val) { - return !(val & _PAGE_PRESENT); + return val && !(val & _PAGE_PRESENT); }
/* Get a mask to xor with the page table entry to get the correct pfn. */
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