Messages in this thread | | | Date | Tue, 11 Apr 2023 21:38:50 -0700 | Subject | Re: [RFC PATCH] x86/fpu/xstate: Add more diagnostic information on inconsistent xstate sizes | From | "Chang S. Bae" <> |
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On 4/11/2023 6:21 PM, Fenghua Yu wrote: > > First of all, max_features is shown already.
Yes.
> Kernel_size from CPUID.0xd.0x1:EBX takes XCR0 | IA32_XSS as input. > Platform may take wrong XCR0 or IA32_XSS and get wrong kernel_size. The > purpose of this patch is to provide more debug info to help debug > platform/kernel issue. So instead of a whole max_features, xgetbv() to > get XCR0 and xfeatures_mask_supervisor() to get IA32_XSS provides more > debug info in case platform may have issue in XCR0 or IA32_XSS. > > In other words, splitting max_features into XCR0 and IA32_XSS and > showing them individually provide more useful debug info than one single > max_features value. > > Does it make sense?
Hmm, I don't get it. I don't think whether the microcode takes those register values wrong or miscalculates the size does matter here.
print_xstate_offset_size() or something can decode the mask and readily shows off how it was calculated here. Then, probably that's it.
>> I still expect some acknowledgment of what is coded here for the >> kernel calculation details. > > The kernel calculation is shown in > + print_xstate_offset_size(); > + pr_info("x86/fpu: total size: %u bytes\n", size); > > Isn't that detailed enough to show offset and size of each xstate and > sum of sizes? > > After that, > + pr_info("x86/fpu: kernel_size from CPUID.0xd.0x%x:EBX: %u bytes\n", > + compacted ? 1 : 0, kernel_size); > shows how kernel_size is calculated from CPUID? > > Using the above debug info, a real platform CPUID issue is shown clearly. > > What other details are needed?
I recall it was also asked to show which features are off or mismatched as compared to the CPU calculation. I'm not so sure about it.
Thanks, Chang
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