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SubjectRe: [PATCHv3 3/3] x86/tdx: Handle load_unaligned_zeropad() page-cross to a shared page
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On 5/26/22 13:36, Kirill A. Shutemov wrote:
> On Thu, May 26, 2022 at 09:20:56AM -0700, Dave Hansen wrote:
>> 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.
> Compiler-generated memory accesses tend to be aligned too. You need to do
> something make them unalinged, like __packed or pointer trickery.

I totally agree. But, the point is that __packed or pointer trickery is
goofy, but it's not necessarily a bug. This might crash the kernel on
goofy stuff, not bugs.

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