Messages in this thread | | | Date | Thu, 26 May 2022 09:20:56 -0700 | Subject | Re: [PATCHv3 3/3] x86/tdx: Handle load_unaligned_zeropad() page-cross to a shared page | From | Dave Hansen <> |
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On 5/24/22 15:10, Kirill A. Shutemov wrote: > + /* > + * MMIO accesses suppose to be naturally aligned and therefore never > + * cross a page boundary. Seeing unaligned accesses indicates a bug or > + * load_unaligned_zeropad() that steps into unmapped shared page.
Wait a sec though...
We've been talking all along about how MMIO accesses are in some cases just plain old compiler-generated memory accesses. It's *probably* bad code that does this, but it's not necessarily a bug.
It's kinda like the split lock detection patches. Those definitely found some stupid stuff, but it wasn't anything that I would have called an outright bug. Plus, in those cases, folks had explicitly opted in to more crashes on stupid stuff.
That stupid stuff _might_ be rare enough that it's still OK to just punt on it and not emulate the instruction (aka. crash). Or, to say that TDX guests are opting in to being more fragile, just like with split lock detection.
But, either of those would call for a very different comment.
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