From: Christian Borntraeger <borntraeger@de.ibm.com>
To: Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>
Cc: x86@kernel.org, Peter Zijlstra <peterz@infradead.org>,
Andy Lutomirski <luto@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Marc Zyngier <maz@kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>,
kvm@vger.kernel.org, linux-arch@vger.kernel.org,
linux-s390 <linux-s390@vger.kernel.org>
Subject: Re: [RFC patch 00/15] entry: Provide generic implementation for host and guest entry/exit work
Date: Tue, 24 Sep 2019 08:50:20 +0200 [thread overview]
Message-ID: <ae5c6329-4ddf-2243-3a86-fbfdfd029918@de.ibm.com> (raw)
In-Reply-To: <20190919150314.054351477@linutronix.de>
On 19.09.19 17:03, Thomas Gleixner wrote:
> When working on a way to move out the posix cpu timer expiry out of the
> timer interrupt context, I noticed that KVM is not handling pending task
> work before entering a guest. A quick hack was to add that to the x86 KVM
> handling loop. The discussion ended with a request to make this a generic
> infrastructure possible with also moving the per arch implementations of
> the enter from and return to user space handling generic.
>
> https://lore.kernel.org/r/89E42BCC-47A8-458B-B06A-D6A20D20512C@amacapital.net
>
> You asked for it, so don't complain that you have to review it :)
>
> The series implements the syscall enter/exit and the general exit to
> userspace work handling along with the pre guest enter functionality.
>
> The series converts x86 and ARM64. x86 is fully tested including selftests
> etc. ARM64 is only compile tested for now as my only ARM64 testbox is not
> available right now.
It seems that s390x would also need to look into TIF_NOTIFY_PENDING before
entering a KVM guest. Given that the s390x entry path is still in assembler
this might not be something to do quickly.
Would it make sense to actually start with a minimal solution (e.g. one that
provides notify_resume_pending like your original patch) as a fix. That would
also be simple to backport. And then we can do the proper rework on top.
Or do we consider anything that depends on TIF_NOTIFY_PENDING before entering
a guest as not important enough for stable?
After all the vcpu_run ioctl almost never returns to userspace and nothing
was obviously broken.
Another question: Are there callbacks due to TIF_NOTIFY_PENDING that should
NOT happen as long as we stay in the vpcu loop?
prev parent reply other threads:[~2019-09-24 6:50 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-19 15:03 [RFC patch 00/15] entry: Provide generic implementation for host and guest entry/exit work Thomas Gleixner
2019-09-19 15:03 ` [RFC patch 01/15] entry: Provide generic syscall entry functionality Thomas Gleixner
2019-09-20 23:38 ` Andy Lutomirski
2019-10-20 11:49 ` Thomas Gleixner
2019-09-23 9:05 ` Mike Rapoport
2019-09-19 15:03 ` [RFC patch 02/15] x86/entry: Remove _TIF_NOHZ from _TIF_WORK_SYSCALL_ENTRY Thomas Gleixner
2019-09-20 23:39 ` Andy Lutomirski
2019-09-23 20:43 ` Thomas Gleixner
2019-09-19 15:03 ` [RFC patch 03/15] x86/entry: Use generic syscall entry function Thomas Gleixner
2019-09-20 23:41 ` Andy Lutomirski
2019-09-23 8:31 ` Peter Zijlstra
2019-09-23 8:40 ` Thomas Gleixner
2019-09-19 15:03 ` [RFC patch 04/15] arm64/entry: " Thomas Gleixner
2019-09-20 12:21 ` Catalin Marinas
2019-09-19 15:03 ` [RFC patch 05/15] entry: Provide generic syscall exit function Thomas Gleixner
2019-09-19 15:03 ` [RFC patch 06/15] x86/entry: Use generic syscall exit functionality Thomas Gleixner
2019-09-19 15:03 ` [RFC patch 07/15] arm64/syscall: Remove obscure flag check Thomas Gleixner
2019-09-20 14:29 ` Catalin Marinas
2019-09-19 15:03 ` [RFC patch 08/15] arm64/syscall: Use generic syscall exit functionality Thomas Gleixner
2019-09-19 15:03 ` [RFC patch 09/15] entry: Provide generic exit to usermode functionality Thomas Gleixner
2019-09-23 8:30 ` Peter Zijlstra
2019-09-19 15:03 ` [RFC patch 10/15] x86/entry: Move irq tracing to C code Thomas Gleixner
2019-09-23 8:47 ` Peter Zijlstra
2019-09-23 10:27 ` Thomas Gleixner
2019-09-23 11:49 ` Peter Zijlstra
2019-09-23 11:55 ` Peter Zijlstra
2019-09-23 12:10 ` Peter Zijlstra
2019-09-23 17:24 ` Andy Lutomirski
2019-09-26 2:59 ` Josh Poimboeuf
2019-09-19 15:03 ` [RFC patch 11/15] x86/entry: Use generic exit to usermode Thomas Gleixner
2019-09-19 15:03 ` [RFC patch 12/15] arm64/entry: " Thomas Gleixner
2019-09-19 15:03 ` [RFC patch 13/15] arm64/entry: Move FPU restore out of exit_to_usermode() loop Thomas Gleixner
2019-09-19 15:03 ` [RFC patch 14/15] workpending: Provide infrastructure for work before entering a guest Thomas Gleixner
2019-09-19 15:40 ` Paolo Bonzini
2019-09-20 11:48 ` Thomas Gleixner
2019-09-23 18:17 ` Andy Lutomirski
2019-09-26 11:35 ` Miroslav Benes
2019-09-19 15:03 ` [RFC patch 15/15] x86/kvm: Use GENERIC_EXIT_WORKPENDING Thomas Gleixner
2019-09-19 15:40 ` Paolo Bonzini
2019-09-20 15:12 ` [RFC patch 00/15] entry: Provide generic implementation for host and guest entry/exit work Mark Rutland
2019-09-23 20:50 ` Thomas Gleixner
2019-09-23 18:18 ` Andy Lutomirski
2019-09-24 6:50 ` Christian Borntraeger [this message]
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