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Groups > linux.kernel > #1548801
| From | Borislav Petkov <bp@alien8.de> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH 1/2] x86/CPU: Add native CPUID variants returning a single datum |
| Date | 2016-12-31 12:20 +0100 |
| Message-ID | <sUpRE-2d9-7@gated-at.bofh.it> (permalink) |
| References | (1 earlier) <sTkAG-7wR-11@gated-at.bofh.it> <sTkAG-7wR-9@gated-at.bofh.it> <sTqZs-3sy-11@gated-at.bofh.it> <sTFlL-4Oj-17@gated-at.bofh.it> <sUhr3-5cP-1@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Fri, Dec 30, 2016 at 06:13:24PM -0800, Andy Lutomirski wrote:
> Now you call it and ignore the return value and the compiler optimizes
> it out :)
Does it, really?
It is an inlined asm volatile. I checked all call sites and the CPUID
call is there. gcc 6 simply issues the CPUID and then later code
overwrites rAX. I.e., it looks ok to me.
Or what example scenario do you have in mind?
> Also, someone reading the code might scratch their head and
> wonder why you picked eax and not ebx, ecx, or edx.
We have comments for her/him :-)
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
--
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[PATCH] x86: Fix Intel microcode revision detection Junichi Nomura <j-nomura@ce.jp.nec.com> - 2016-12-28 05:50 +0100
[PATCH 1/2] x86/CPU: Add native CPUID variants returning a single datum Borislav Petkov <bp@alien8.de> - 2016-12-28 12:30 +0100
Re: [PATCH 1/2] x86/CPU: Add native CPUID variants returning a single datum Andy Lutomirski <luto@amacapital.net> - 2016-12-28 19:20 +0100
Re: [PATCH 1/2] x86/CPU: Add native CPUID variants returning a single datum Borislav Petkov <bp@alien8.de> - 2016-12-29 10:40 +0100
Re: [PATCH 1/2] x86/CPU: Add native CPUID variants returning a single datum Andy Lutomirski <luto@amacapital.net> - 2016-12-31 03:20 +0100
Re: [PATCH 1/2] x86/CPU: Add native CPUID variants returning a single datum Borislav Petkov <bp@alien8.de> - 2016-12-31 12:20 +0100
[PATCH 2/2] x86/microcode: Use native CPUID to tickle out microcode revision Borislav Petkov <bp@alien8.de> - 2016-12-28 12:30 +0100
[PATCH 3/2] x86/microcode/intel: Add a helper which gives the microcode revision Borislav Petkov <bp@alien8.de> - 2016-12-28 14:00 +0100
Re: [PATCH 3/2] x86/microcode/intel: Add a helper which gives the microcode revision Andy Lutomirski <luto@amacapital.net> - 2016-12-28 19:20 +0100
Re: [PATCH 3/2] x86/microcode/intel: Add a helper which gives the microcode revision Borislav Petkov <bp@alien8.de> - 2016-12-29 10:40 +0100
Re: [PATCH 3/2] x86/microcode/intel: Add a helper which gives the microcode revision Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-12-28 20:30 +0100
Re: [PATCH 3/2] x86/microcode/intel: Add a helper which gives the microcode revision Borislav Petkov <bp@alien8.de> - 2016-12-29 10:40 +0100
Re: [PATCH] x86: Fix Intel microcode revision detection Borislav Petkov <bp@alien8.de> - 2016-12-28 12:30 +0100
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