From: Peter Zijlstra <peterz@infradead.org>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Juergen Gross <jgross@suse.com>, Per Bilse <Per.Bilse@citrix.com>,
Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
Stefano Stabellini <sstabellini@kernel.org>,
Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>,
"open list:X86 ENTRY CODE" <linux-kernel@vger.kernel.org>,
"moderated list:XEN HYPERVISOR INTERFACE"
<xen-devel@lists.xenproject.org>
Subject: Re: [PATCH] Updates to Xen hypercall preemption
Date: Thu, 22 Jun 2023 15:14:45 +0200 [thread overview]
Message-ID: <20230622131445.GQ4253@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <e8f0d101-d803-8ccb-80a0-fc7c6c45ab77@citrix.com>
On Thu, Jun 22, 2023 at 02:05:13PM +0100, Andrew Cooper wrote:
> On 22/06/2023 9:26 am, Peter Zijlstra wrote:
> > On Thu, Jun 22, 2023 at 07:22:53AM +0200, Juergen Gross wrote:
> >
> >> The hypercalls we are talking of are synchronous ones. They are running
> >> in the context of the vcpu doing the call (like a syscall from userland is
> >> running in the process context).
> > (so time actually passes from the guest's pov?)
>
> Yes. And in principle it's wired into stolen time.
Hmm, that means that if the scheduler accounts for stolen time (see
update_rq_clock_task(), PARAVIRT_TIME_ACCOUNTING hunk) then it appears
as if no time has passed, which might affect preemption decisions.
Oh well, we'll think about it when it's shown to be a problem I suppose
:-)
next prev parent reply other threads:[~2023-06-22 13:15 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-21 15:14 [PATCH] Updates to Xen hypercall preemption Per Bilse
2023-06-21 16:27 ` Andy Lutomirski
2023-06-21 19:05 ` Per Bilse
2023-06-21 23:42 ` Andy Lutomirski
2023-06-21 16:40 ` Peter Zijlstra
2023-06-21 19:19 ` Per Bilse
2023-06-21 20:04 ` Peter Zijlstra
2023-06-22 5:22 ` Juergen Gross
2023-06-22 8:26 ` Peter Zijlstra
2023-06-22 10:33 ` Juergen Gross
2023-06-22 11:15 ` Peter Zijlstra
2023-06-22 12:17 ` Juergen Gross
2023-06-22 16:39 ` Andy Lutomirski
2023-06-22 17:20 ` Juergen Gross
2023-06-24 15:19 ` Andy Lutomirski
2023-06-22 13:05 ` Andrew Cooper
2023-06-22 13:14 ` Peter Zijlstra [this message]
2023-06-22 13:35 ` Juergen Gross
2023-06-22 10:01 ` Per Bilse
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