lists.openwall.net | 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 linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Fri, 03 Sep 2010 16:46:03 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Matt Domsch <Matt_Domsch@...l.com> Cc: Arjan van de Ven <arjan@...ux.intel.com>, Ingo Molnar <mingo@...e.hu>, Stephane Eranian <eranian@...gle.com>, "robert.richter" <robert.richter@....com>, Linus Torvalds <torvalds@...ux-foundation.org>, LKML <linux-kernel@...r.kernel.org>, "H. Peter Anvin" <hpa@...ux.kernel.org> Subject: Re: [PATCH] perf, x86: Disable perf if the BIOS got its grubby paws on the PMU On Fri, 2010-09-03 at 09:32 -0500, Matt Domsch wrote: > On Fri, Sep 03, 2010 at 06:53:59AM -0700, Arjan van de Ven wrote: > > On 9/3/2010 2:13 AM, Peter Zijlstra wrote: > > > > > >+static void print_BIOS_fail(void) > > >+{ > > >+ printk(KERN_ERR "\n"); > > >+ printk(KERN_ERR "=============================================\n"); > > >+ printk(KERN_ERR "It appears the BIOS is actively using the PMU\n"); > > >+ printk(KERN_ERR "this avoids Linux from using it, please de- \n"); > > >+ printk(KERN_ERR "activate this BIOS feature or request a BIOS \n"); > > >+ printk(KERN_ERR "update from your vendor. \n"); > > >+ printk(KERN_ERR "=============================================\n"); > > >+ > > >+ memset(&x86_pmu, 0, sizeof(x86_pmu)); > > >+} > I must object to messages that repeatedly (at least on every boot) > tell system administrators to contact their hardware vendor's support > lines, when it's not clear what the BIOS is doing is incorrect. It is using the PMU, it should not _ever_ do that. > There > are plenty of valid reasons why BIOS itself would use PMU counters. > Dell PowerEdge server power management, handled by the BIOS, certainly > does use one. Them make them stop doing that, or at least provide a BIOS option to disable this Feat^WFailure-add. An no, doing power-management from the BIOS is most certainly not a valid reason. That's not what BIOSes are for, a BIOS should bring up the system and then sod off. > My understanding is that there is a mechanism for the OS to request > BIOS to release use of PMU counters. Are we doing that? I'm not aware of any such thing. The Intel Arch docs most certainly don't specify anything about that. > If BIOS does > not release the counters when asked, ok, that's something to > (potentially) warn about. But blanket "BIOS is using a CPU feature! > Bad BIOS! No treat for you!" - that's not helpful to anyone. Again, I'm not aware there is a spec on how to ask anything of the BIOS, let alone a part pertaining to PMU functionality. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists