linux-kernel - Re: [PATCH] x86/xen/time: Reduce Xen timer tick

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]

Date: Mon, 17 Jun 2024 16:22:21 +0200
From: Jan Beulich <jbeulich@...e.com>
To: Frediano Ziglio <frediano.ziglio@...ud.com>
Cc: "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
 Dave Hansen <dave.hansen@...ux.intel.com>, Borislav Petkov <bp@...en8.de>,
 Ingo Molnar <mingo@...hat.com>, Thomas Gleixner <tglx@...utronix.de>,
 Boris Ostrovsky <boris.ostrovsky@...cle.com>, Juergen Gross
 <jgross@...e.com>, xen-devel@...ts.xenproject.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/xen/time: Reduce Xen timer tick

On 17.06.2024 16:13, Frediano Ziglio wrote:
> Current timer tick is causing some deadline to fail.
> The current high value constant was probably due to an old
> bug in the Xen timer implementation causing errors if the
> deadline was in the future.
> This was fixed in Xen commit:
> 19c6cbd90965 xen/vcpu: ignore VCPU_SSHOTTMR_future

And then newer kernels are no longer reliably usable on Xen older than
this?

> --- a/arch/x86/xen/time.c
> +++ b/arch/x86/xen/time.c
> @@ -30,7 +30,7 @@
>  #include "xen-ops.h"
>  
>  /* Minimum amount of time until next clock event fires */
> -#define TIMER_SLOP	100000
> +#define TIMER_SLOP	1000

It may be just the lack of knowledge of mine towards noadays's Linux'es
time handling, but the change of a value with this name and thus
commented doesn't directly relate to "timer tick" rate. Could you maybe
help me see the connection?

Jan