linux-kernel - Re: [PATCH 3/4] rseq: Make rseq work with protection keys

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Message-ID: <f0a2dc31-1040-43f8-968d-345acc8a543d@intel.com>
Date: Fri, 21 Feb 2025 13:40:50 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Dmitry Vyukov <dvyukov@...gle.com>, peterz@...radead.org,
 boqun.feng@...il.com, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com, hpa@...or.com, aruna.ramakrishna@...cle.com,
 elver@...gle.com
Cc: "Paul E. McKenney" <paulmck@...nel.org>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] rseq: Make rseq work with protection keys

On 2/21/25 13:11, Mathieu Desnoyers wrote:
> I have no clue what a "remote" pkey access is. Is this the io_uring
> use-case ?

Yeah, that's one of them.

It's basically all of the *_user_pages_remote() sites which are places
that the kernel does userspace memory manipulation but doesn't have a
good user *context* with which to do it, thus no good PKRU value.

The "remote" nomenclature is because these are mostly (all??) one
process accessing another process without that other process really
being involved.