Re: kern/50332: AVX instructions don't work but OSXSAVE flag is set

[tg%gmplib.org@localhost (Torbjörn Granlund)]

The following reply was made to PR kern/50332; it has been noted by GNATS.

From: tg%gmplib.org@localhost (=?utf-8?Q?Torbj=C3=B6rn?= Granlund)
To: gnats-bugs%NetBSD.org@localhost
Cc: kern-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost
Subject: Re: kern/50332: AVX instructions don't work but OSXSAVE flag is set
Date: Tue, 13 Oct 2015 09:09:44 +0200

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    If this is a bug in NetBSD, it's also a bug on this Linux:
    
    Linux eternium 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt11-1+deb8u4 (2015-09-19) x86_64 GNU/Linux
    
    on a:
    
    model name	: Intel(R) Core(TM)2 Duo CPU     E8600  @ 3.33GHz
    
    CPU.
    
 This CPU does not support AVX.
 
    Nothing I see says that OSXSAVE implies that AVX instructions are
    implemented and working.  According to:
    
    https://software.intel.com/en-us/blogs/2011/04/14/is-avx-enabled/
    
    the AVX flag (bit 28) also needs to be asserted.
    
 The test case demos a real bug, please don't dismiss it because a CPU
 without AVX cannot execute AVX instructions.
 
 In practice, one of course also tests for AVX.  I modified the testcase
 to do that in order to clarify things.  Attached.
 
 This does not fail on Linux, FreeBSD, OpenBSD, etc.  It does fail on
 NetBSD.  Let me be clear: To see this AVX error, one needs a computer
 with AVX hardware.
 
 I've reproduced this on an Intel haswell system, an AMD bulldozer
 system, and an AMD piledriver system.  All these systems run some
 version of NetBSD 7.0 as Dom0, either a prerelease or the release.
 
 I've also reproduced it under NetBSD 6.1.x and NetBSD 7.0 in a DomU.  On
 the same machines, Linux and FreeBSD DomUs run the testcase fine.
 
 
 
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