linux-kernel - Re: [patch V2 23/37] rseq: Provide and use rseq_set

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Message-ID: <a5d17e1f-ee63-4e13-ae3d-c6404d411b32@efficios.com>
Date: Thu, 4 Sep 2025 13:25:05 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Thomas Gleixner <tglx@...utronix.de>, LKML <linux-kernel@...r.kernel.org>
Cc: Jens Axboe <axboe@...nel.dk>, Peter Zijlstra <peterz@...radead.org>,
 "Paul E. McKenney" <paulmck@...nel.org>, Boqun Feng <boqun.feng@...il.com>,
 Paolo Bonzini <pbonzini@...hat.com>, Sean Christopherson
 <seanjc@...gle.com>, Wei Liu <wei.liu@...nel.org>,
 Dexuan Cui <decui@...rosoft.com>, x86@...nel.org,
 Arnd Bergmann <arnd@...db.de>, Heiko Carstens <hca@...ux.ibm.com>,
 Christian Borntraeger <borntraeger@...ux.ibm.com>,
 Sven Schnelle <svens@...ux.ibm.com>, Huacai Chen <chenhuacai@...nel.org>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>
Subject: Re: [patch V2 23/37] rseq: Provide and use rseq_set_uids()

On 2025-09-02 12:33, Thomas Gleixner wrote:
> On Tue, Sep 02 2025 at 16:08, Thomas Gleixner wrote:
>> On Tue, Aug 26 2025 at 10:52, Mathieu Desnoyers wrote:
>>>> +
>>>> +	/* Cache the new values */
>>>> +	t->rseq_ids.cpu_cid = ids->cpu_cid;
>>>
>>> I may be missing something, but I think we're missing updates to
>>> t->rseq_ids.mm_cid and we may want to keep track of t->rseq_ids.node_id
>>> as well.
>>
>> Oops. I'm sure I had that mm_cid caching, but somehow dropped it. And
>> again, no need to keep track of the node id. It's stable vs. CPU ID.
> 
> Correcting myself. You are missing that this caches the compound value
> and not only the CPU id.

OK, yes. Thanks for the clarification , I indeed missed that.

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com