Messages in this thread | | | Date | Mon, 7 Nov 2022 21:43:29 +0800 | Subject | Re: [PATCH 2/2] x86/tdx: Do not allow #VE due to EPT violation on the private memory | From | Guorui Yu <> |
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在 2022/11/7 21:31, Dave Hansen 写道: > On 11/6/22 21:10, Guorui Yu wrote: >>> Without ATTR_SEPT_VE_DISABLE, a #VE can occur on basically any >>> instruction. We call those kinds of exceptions "paranoid entry" points. >>> They need special handling like the NMI or #MC handlers. >>> >>> I'd be happy to look at a patch that does the MMIO path check *and* >>> turns the #VE handler into a robust entry point. >>> >>> Bonus points if you can do ~5 lines of C like the approach in this >>> thread. >> >> Yes, there is a fix to satify your requirement and get the bouns points 😄 >> >> Please refer to >> https://github.com/intel/tdx/commit/f045b0d52a5f7d8bf66cd4410307d05a90523f10 >> >> case EXIT_REASON_EPT_VIOLATION: >> + if (!(ve->gpa & tdx_shared_mask())) { >> + panic("#VE due to access to unaccepted memory. " >> + "GPA: %#llx\n", ve->gpa); >> + } >> + >> /* original from Kirill and Kuppuswamy */ >> >> It's already there, but it just didn't get into the main branch. > > Could you explain how that prevents the #VE from occurring in the > "syscall gap" or in a place where the kernel is running with the user > GSBASE value? > Thank you for explaining the "paranoid entry" points with there examples to me, now I understand why the SEPT_VE_DISABLE is necessary for TD.
> It doesn't as far as I can tell. You need the SEPT_VE_DISABLE check for > that.
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