From: "Michael S. Tsirkin" <mst@redhat.com>
To: "Alex Bennée" <alex.bennee@linaro.org>
Cc: "Manos Pitsidianakis" <manos.pitsidianakis@linaro.org>,
qemu-devel@nongnu.org,
"Philippe Mathieu-Daudé" <philmd@linaro.org>,
"Richard Henderson" <richard.henderson@linaro.org>,
"Stefan Hajnoczi" <stefanha@redhat.com>
Subject: Re: [PATCH v2 0/3] virtio-gpu: fix blob unmapping sequence
Date: Wed, 16 Apr 2025 14:57:32 -0400 [thread overview]
Message-ID: <20250416145701-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <87v7r5clft.fsf@draig.linaro.org>
On Tue, Apr 15, 2025 at 07:46:14PM +0100, Alex Bennée wrote:
> Manos Pitsidianakis <manos.pitsidianakis@linaro.org> writes:
>
> > A hang was observed when running a small kernel that exercised VIRTIO
> > GPU under TCG. This is an edge-case and won't happen under typical
> > conditions.
>
> Should I (or MST?) pull these into a tree for 10.0 or should they be
> grabbed for when the tree opens with a Cc qemu-stable?
Let's just agree who takes them, then it's up to that maintainer.
You wanna merge them?
> >
> > When unmapping a blob object, its MemoryRegion's freeing is deferred to
> > the RCU thread. The hang's cause was determined to be a busy main loop
> > not allowing for the RCU thread to run because the kernel did not setup
> > any timers or had any interrupts on the way. While fixing the RCU thread
> > to run even if the guest CPU spins is a solution, it's easier to fix the
> > reason why the MemoryRegion isn't freed from the main loop instead.
> >
> > While at it, also restructure the 3 stage cleanup to immediately respond
> > to the guest if the MR happened to have had no other reference.
> >
> > PS: The hang can be reproduced by running this unikernel with TCG
> >
> > https://git.codelinaro.org/manos.pitsidianakis/virtio-tests/-/tree/8c0ebe9395827e24aa5711186d499bf5de87cf63/virtio-test-suite
> >
> > v1 to v2:
> > - Add patch by Alex to prevent double-free when FlatView is destroyed
> > from RCU thread.
> >
> > Alex Bennée (1):
> > hw/display: re-arrange memory region tracking
> >
> > Manos Pitsidianakis (2):
> > virtio-gpu: fix hang under TCG when unmapping blob
> > virtio-gpu: refactor async blob unmapping
> >
> > include/exec/memory.h | 1 +
> > hw/display/virtio-gpu-virgl.c | 60 ++++++++++++++++++++---------------
> > 2 files changed, 35 insertions(+), 26 deletions(-)
> >
> >
> > base-commit: 56c6e249b6988c1b6edc2dd34ebb0f1e570a1365
>
> --
> Alex Bennée
> Virtualisation Tech Lead @ Linaro
next prev parent reply other threads:[~2025-04-16 18:58 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-04-10 12:26 [PATCH v2 0/3] virtio-gpu: fix blob unmapping sequence Manos Pitsidianakis
2025-04-10 12:26 ` [PATCH v2 1/3] hw/display: re-arrange memory region tracking Manos Pitsidianakis
2025-04-15 10:35 ` Philippe Mathieu-Daudé
2025-04-15 11:21 ` Alex Bennée
2025-04-10 12:26 ` [PATCH v2 2/3] virtio-gpu: fix hang under TCG when unmapping blob Manos Pitsidianakis
2025-04-10 14:59 ` Alex Bennée
2025-04-10 12:26 ` [PATCH v2 3/3] virtio-gpu: refactor async blob unmapping Manos Pitsidianakis
2025-04-15 10:40 ` Philippe Mathieu-Daudé
2025-04-15 18:46 ` [PATCH v2 0/3] virtio-gpu: fix blob unmapping sequence Alex Bennée
2025-04-16 18:57 ` Michael S. Tsirkin [this message]
2025-04-17 8:00 ` Alex Bennée
2025-04-17 11:37 ` Michael S. Tsirkin
2025-04-16 19:26 ` Stefan Hajnoczi
2025-04-17 8:08 ` Alex Bennée
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