From: Andy Lutomirski <luto@amacapital.net>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: "Van De Ven, Arjan" <arjan.van.de.ven@intel.com>,
"Hansen, Dave" <dave.hansen@intel.com>,
LKML <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linuxfoundation.org>,
"x86@kernel.org" <x86@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Borislav Petkov <bp@alien8.de>,
David Woodhouse <dwmw@amazon.co.uk>,
Tim Chen <tim.c.chen@linux.intel.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Andi Kleen <ak@linux.intel.com>,
Greg KH <gregkh@linuxfoundation.org>,
Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@suse.de>,
"Raj, Ashok" <ashok.raj@intel.com>
Subject: Re: [patch RFC 1/5] x86/CPU: Sync CPU feature flags late
Date: Tue, 9 Jan 2018 18:57:32 -0800 [thread overview]
Message-ID: <96FD6D6D-4D56-492F-A996-F18F913F5091@amacapital.net> (raw)
In-Reply-To: <alpine.DEB.2.20.1801100245010.2200@nanos>
> On Jan 9, 2018, at 5:47 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
>
> On Wed, 10 Jan 2018, Van De Ven, Arjan wrote:
>>> In other words, if you use late microcode loading for getting IBRS, you
>>> don't get ALTERNATIVE patching and its benefits?
>>>
>>> I'll also profess some microcode ignorance here. Is "late microcode
>>> patching" *all* of the stuff we do from the OS, or do we have early and
>>> late Linux loading in addition to what the BIOS can do?
>>
>> the early boot loader level stuff is much better generally (but does not
>> work when the microcode comes out after the system booted... like really
>> long uptimes)
>
> That stuff indeed would be way simpler w/o the late support, but the fact
> that the microcode for this might reach the user way later than the kernel
> support makes it almost a must to support the late loading.
How hard would it be to add a late alternative feature? Concretely, we'd have a list of "late" cpufeatures. When we scan the alternative list, if we find a late feature, we copy it to some other list that isn't discarded, and we also copy its replacement (and relocate it eagerly, since we'll lose the offset).
next prev parent reply other threads:[~2018-01-10 2:57 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-10 1:06 [patch RFC 0/5] x86/spectre_v2: Initial integration of IBRS into the spectre_v2 mechanics Thomas Gleixner
2018-01-10 1:06 ` [patch RFC 1/5] x86/CPU: Sync CPU feature flags late Thomas Gleixner
2018-01-10 1:37 ` Dave Hansen
2018-01-10 1:39 ` Van De Ven, Arjan
2018-01-10 1:47 ` Thomas Gleixner
2018-01-10 2:57 ` Andy Lutomirski [this message]
2018-01-10 11:02 ` Thomas Gleixner
2018-01-10 1:44 ` Thomas Gleixner
2018-01-10 6:20 ` Ingo Molnar
2018-01-10 11:33 ` Borislav Petkov
2018-01-10 12:38 ` Thomas Gleixner
2018-01-10 1:06 ` [patch RFC 2/5] x86/spectre: Simplify spectre code a bit Thomas Gleixner
2018-01-10 6:22 ` Ingo Molnar
2018-01-10 1:06 ` [patch RFC 3/5] x86/spectre: Prepare for IBRS selection Thomas Gleixner
2018-01-10 1:51 ` Dave Hansen
2018-01-10 1:06 ` [patch RFC 4/5] x86/cpufeatures: Detect Speculation control feature Thomas Gleixner
2018-01-10 6:32 ` Ingo Molnar
2018-01-10 11:06 ` Thomas Gleixner
2018-01-10 1:06 ` [patch RFC 5/5] x86/speculation: Add basic speculation control code Thomas Gleixner
2018-01-10 2:02 ` Dave Hansen
2018-01-10 4:11 ` Justin Forbes
2018-01-10 9:22 ` Peter Zijlstra
2018-01-10 9:27 ` David Woodhouse
2018-01-10 10:03 ` Peter Zijlstra
2018-01-10 11:22 ` David Woodhouse
2018-01-10 11:41 ` Thomas Gleixner
2018-01-10 11:45 ` Peter Zijlstra
2018-01-10 11:54 ` Andrea Arcangeli
2018-01-10 11:58 ` David Woodhouse
2018-01-10 12:01 ` Andrea Arcangeli
2018-01-10 12:07 ` Andrea Arcangeli
2018-01-10 12:12 ` David Woodhouse
2018-01-10 12:20 ` Andrea Arcangeli
2018-01-10 12:27 ` Andrea Arcangeli
2018-01-10 13:42 ` Van De Ven, Arjan
2018-01-10 12:09 ` David Woodhouse
2018-01-10 12:17 ` Andrea Arcangeli
2018-01-10 12:29 ` David Woodhouse
2018-01-10 12:41 ` Andrea Arcangeli
2018-01-10 12:47 ` Jiri Kosina
2018-01-10 12:51 ` David Woodhouse
2018-01-10 13:02 ` Andrea Arcangeli
2018-01-10 13:05 ` Andrea Arcangeli
2018-01-10 13:10 ` Andrea Arcangeli
2018-01-10 13:12 ` Andrea Arcangeli
2018-01-10 12:57 ` Andrea Arcangeli
2018-01-10 13:07 ` David Woodhouse
2018-01-10 13:45 ` Van De Ven, Arjan
2018-01-10 13:52 ` Andrea Arcangeli
2018-01-10 13:53 ` Van De Ven, Arjan
2018-01-10 21:35 ` Tim Chen
2018-01-10 22:13 ` Andrea Arcangeli
2018-01-10 13:46 ` Thomas Gleixner
2018-01-10 13:51 ` Van De Ven, Arjan
2018-01-10 13:53 ` Thomas Gleixner
2018-01-10 13:58 ` David Woodhouse
2018-01-10 14:10 ` Andrea Arcangeli
2018-01-10 14:14 ` Van De Ven, Arjan
2018-01-10 14:59 ` Dave Hansen
2018-01-10 15:13 ` Andrea Arcangeli
2018-01-10 15:24 ` David Woodhouse
2018-01-10 15:47 ` Andrea Arcangeli
2018-01-10 15:56 ` David Woodhouse
2018-01-10 13:10 ` Jiri Kosina
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