linux-kernel - Re: [RFC PATCH v4 5/8] x86/mm: Introduce Remote Action Request

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: <xrshtiuedxfwh5iabo3eq7y5sskpkwh45mi36xy72bja6ceoqy@3phukaxf4bvc>
Date: Thu, 26 Jun 2025 18:54:27 +0300
From: "Kirill A. Shutemov" <kirill@...temov.name>
To: Rik van Riel <riel@...riel.com>
Cc: linux-kernel@...r.kernel.org, kernel-team@...a.com, 
	dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org, bp@...en8.de, 
	x86@...nel.org, nadav.amit@...il.com, seanjc@...gle.com, tglx@...utronix.de, 
	mingo@...nel.org, Yu-cheng Yu <yu-cheng.yu@...el.com>
Subject: Re: [RFC PATCH v4 5/8] x86/mm: Introduce Remote Action Request

On Thu, Jun 26, 2025 at 06:41:09PM +0300, Kirill A. Shutemov wrote:
> > +	/*
> > +	 * Allow RAR events to be processed while interrupts are disabled on
> > +	 * a target CPU. This prevents "pileups" where many CPUs are waiting
> > +	 * on one CPU that has IRQs blocked for too long, and should reduce
> > +	 * contention on the rar_payload table.
> > +	 */
> > +	wrmsrl(MSR_IA32_RAR_CTRL, RAR_CTRL_ENABLE | RAR_CTRL_IGNORE_IF);
> 
> Hmm. How is RAR_CTRL_IGNORE_IF safe? Wouldn't it break GUP_fast() which
> relies on disabling interrupts to block TLB flush and page table freeing?

Ah. I missed that x86 switched to MMU_GATHER_RCU_TABLE_FREE.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov