lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Thu, 18 Sep 2014 17:28:08 -0700
From:	"H. Peter Anvin" <>
To:	Andy Lutomirski <>,
	Henrique de Moraes Holschuh <>
CC:	Borislav Petkov <>,
	Chuck Ebbert <>,
	"" <>
Subject: Re: x86, microcode: BUG: microcode update that changes x86_capability

The cpuid bit gets twiddled...

On September 18, 2014 5:23:40 PM PDT, Andy Lutomirski <> wrote:
>On Sep 18, 2014 5:13 PM, "Henrique de Moraes Holschuh" <>
>> On Thu, 18 Sep 2014, Henrique de Moraes Holschuh wrote:
>> > On Thu, 18 Sep 2014, H. Peter Anvin wrote:
>> > > We should, but this is also part of why we want the early ucode
>> >
>> > Well, yes.  But that won't help the several stable and LTS distros
>> > kernels without early ucode update support.
>> Here's a plan that might work, pending actually checking the
>libpthread TSX
>> code to make sure it keys on /proc/cpuinfo flags:
>Surely it checks cpuid directly, though.
>Can we twiddle the cpuid bit?  I never noticed any way in the docs to
>do it, but if BIOS has such an ability, maybe we do, too.  I wonder if
>there's anything semi-documented in biosbits, or if we could just
>reverse-engineer it.
>> Add a cpu quirk, triggered by the Haswell cpuids, to force-disable
>hle on
>> the affected processors.
>> This will work around the x86_capability capability issue (which
>> still be fixed, anyway), and it should also get userspace to stay
>away from
>> TSX, therefore also working around the worst issue (processes getting
>> This will disable the "user may ask the BIOS to keep TSX enabled"
>> anti-feature, though.  This drawback can be avoided, but only if a
>> microcode update won't re-disable hle when the BIOS enabled it.  For
>now, I
>> suggest that we decree that "hle is toast" for the current Haswells
>and add
>> back ways to enable it for testing when we know more about it.
>> --
>>   "One disk to rule them all, One disk to find them. One disk to
>>   them all and in the darkness grind them. In the Land of Redmond
>>   where the shadows lie." -- The Silicon Valley Tarot
>>   Henrique Holschuh

Sent from my mobile phone.  Please pardon brevity and lack of formatting.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

Powered by blists - more mailing lists