linux-kernel - Re: [PATCHv2] efi/unaccepted: Fix soft lockups caused by parallel memory acceptance

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <CAMj1kXFc31N61=oQayLbnR+CrNT4=bfEisC3fwG4VNq2vJHV5w@mail.gmail.com>
Date:   Tue, 17 Oct 2023 09:42:13 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Matthew Wilcox <willy@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Joerg Roedel <jroedel@...e.de>,
        Andi Kleen <ak@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Tom Lendacky <thomas.lendacky@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Dario Faggioli <dfaggioli@...e.com>,
        Mike Rapoport <rppt@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        marcelo.cerri@...onical.com, tim.gardner@...onical.com,
        philip.cox@...onical.com, aarcange@...hat.com, peterx@...hat.com,
        x86@...nel.org, linux-mm@...ck.org, linux-coco@...ts.linux.dev,
        linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...nel.org, Nikolay Borisov <nik.borisov@...e.com>
Subject: Re: [PATCHv2] efi/unaccepted: Fix soft lockups caused by parallel
 memory acceptance

On Mon, 16 Oct 2023 at 23:39, Kirill A. Shutemov
<kirill.shutemov@...ux.intel.com> wrote:
>
> On Mon, Oct 16, 2023 at 06:55:41PM +0100, Matthew Wilcox wrote:
> > On Mon, Oct 16, 2023 at 07:31:22PM +0300, Kirill A. Shutemov wrote:
> > >   v2:
> > >    - Fix deadlock (Vlastimil);
> > >    - Fix comments (Vlastimil);
> > >    - s/cond_resched()/cpu_relax()/ -- cond_resched() cannot be called
> > >      from atomic context;
> >
> > Isn't there an implicit cpu_relax() while we're spinning?  Does this
> > really accomplish anything?
>
> You are right. It is useless. I will drop it in v3.
>

I can drop that bit when applying the patch.

One question I have is whether the sequence

spin_lock_irqsave(&unaccepted_memory_lock, flags);
...
spin_unlock(&unaccepted_memory_lock);
arch_accept_memory(phys_start, phys_end);
spin_lock(&unaccepted_memory_lock);
...
spin_unlock_irqrestore(&unaccepted_memory_lock, flags);

is considered sound and is supported by all architectures?