Messages in this thread | | | Date | Wed, 15 Jun 2022 08:27:52 -0700 | Subject | Re: [PATCHv4 3/3] x86/tdx: Handle load_unaligned_zeropad() page-cross to a shared page | From | Dave Hansen <> |
| |
On 6/14/22 05:01, Kirill A. Shutemov wrote: > load_unaligned_zeropad() can lead to unwanted loads across page boundaries. > The unwanted loads are typically harmless. But, they might be made to > totally unrelated or even unmapped memory. load_unaligned_zeropad() > relies on exception fixup (#PF, #GP and now #VE) to recover from these > unwanted loads. > > In TDX guests, the second page can be shared page and VMM may configure > it to trigger #VE. > > Kernel assumes that #VE on a shared page is MMIO access and tries to > decode instruction to handle it. In case of load_unaligned_zeropad() it > may result in confusion as it is not MMIO access. > > Fix it by detecting split page MMIO accesses and fail them. > load_unaligned_zeropad() will recover using exception fixups. > > The issue was discovered by analysis. It was not triggered during the > testing.
I thought this whole exercise was kicked off by hitting this in testing. Am I remembering this wrong?
> https://lore.kernel.org/all/20220517153444.11195-10-kirill.shutemov@linux.intel.com/
Says:
> This is an actual, real-world problem which was discovered during TDX > testing.
Or were you considering this a different problem somehow?
| |