linux-kernel - Re: linux-next regression: SNP Guest boot hangs with certain cpu/mem config combination

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

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <2kwzi2qxqualhskbgckk6m7oc6vsgupquceqgfx2gnz5xbkier@rwdrhym7yxhr>
Date: Thu, 27 Mar 2025 19:39:21 +0200
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Jason Baron <jbaron@...mai.com>, Peter Zijlstra <peterz@...radead.org>, 
	Josh Poimboeuf <jpoimboe@...nel.org>, Ard Biesheuvel <ardb@...nel.org>, 
	Tom Lendacky <thomas.lendacky@....com>, "Aithal, Srikanth" <sraithal@....com>, 
	Linux-Next Mailing List <linux-next@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>, 
	"Roth, Michael" <Michael.Roth@....com>
Subject: Re: linux-next regression: SNP Guest boot hangs with certain cpu/mem
 config combination

On Thu, Mar 27, 2025 at 11:02:24AM -0400, Steven Rostedt wrote:
> On Thu, 27 Mar 2025 16:43:43 +0200
> "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> wrote:
> 
> > > > The only option I see so far is to drop static branch from this path.
> > > > 
> > > > But I am not sure if it the only case were we use static branch from CPU
> > > > hotplug callbacks.
> > > > 
> > > > Any other ideas?  
> > > 
> > > 
> > > Hmmm, didn't take too close a look here, but there is the
> > > static_key_slow_dec_cpuslocked() variant, would that work here? Is the issue
> > > the caller may or may not have the cpu_hotplug lock?  
> > 
> > Yes. This is generic page alloc path and it can be called with and without
> > the lock.
> 
> Note, it's not the static_branch that is an issue, it's enabling/disabling
> the static branch that is. Changing a static branch takes a bit of work as
> it does modify the kernel text.
> 
> Is it possible to delay the update via a workqueue?

Ah. Good point. Should work. I'll give it try.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov