From: Oliver Upton <oliver.upton@linux.dev>
To: Marc Zyngier <maz@kernel.org>
Cc: kvmarm@lists.linux.dev, kvm@vger.kernel.org,
James Morse <james.morse@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Zenghui Yu <yuzenghui@huawei.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 07/23] KVM: arm64: vgic: Use atomics to count LPIs
Date: Wed, 14 Feb 2024 23:01:04 +0000 [thread overview]
Message-ID: <Zc1GMFjvy_f1KsXr@linux.dev> (raw)
In-Reply-To: <86wmr64xyo.wl-maz@kernel.org>
On Wed, Feb 14, 2024 at 08:01:19PM +0000, Marc Zyngier wrote:
> > > Of course, we only have 3 marks, so that's a bit restrictive from a
> > > concurrency perspective, but since most callers hold a lock, it should
> > > be OK.
> >
> > They all hold *a* lock, but maybe not the same one! :)
>
> Indeed. But as long as there isn't more than 3 locks (and that the
> xarray is OK being concurrently updated with marks), we're good!
Oh, you mean to give each existing caller their own mark?
> > Maybe we should serialize the use of markers on the LPI list on the
> > config_lock. A slight misuse, but we need a mutex since we're poking at
> > guest memory. Then we can go through the whole N-dimensional locking
> > puzzle and convince ourselves it is still correct.
>
> Maybe. This thing is already seeing so many abuses that one more may
> not matter much. Need to see how it fits in the whole hierarchy of
> GIC-related locks...
It doesn't work. We have it that the config_lock needs to be taken
outside the its_lock.
Too many damn locks!
--
Thanks,
Oliver
next prev parent reply other threads:[~2024-02-14 23:01 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-13 9:32 [PATCH v2 00/23] KVM: arm64: Improvements to LPI injection Oliver Upton
2024-02-13 9:32 ` [PATCH v2 01/23] KVM: arm64: Add tracepoints + stats for LPI cache effectiveness Oliver Upton
2024-02-14 15:55 ` Marc Zyngier
2024-02-13 9:32 ` [PATCH v2 02/23] KVM: arm64: vgic: Store LPIs in an xarray Oliver Upton
2024-02-13 21:52 ` Oliver Upton
2024-02-13 9:32 ` [PATCH v2 03/23] KVM: arm64: vgic: Use xarray to find LPI in vgic_get_lpi() Oliver Upton
2024-02-13 9:32 ` [PATCH v2 04/23] KVM: arm64: vgic-v3: Iterate the xarray to find pending LPIs Oliver Upton
2024-02-13 9:32 ` [PATCH v2 05/23] KVM: arm64: vgic-its: Walk the LPI xarray in vgic_copy_lpi_list() Oliver Upton
2024-02-13 9:32 ` [PATCH v2 06/23] KVM: arm64: vgic: Get rid of the LPI linked-list Oliver Upton
2024-02-13 9:32 ` [PATCH v2 07/23] KVM: arm64: vgic: Use atomics to count LPIs Oliver Upton
2024-02-14 16:47 ` Marc Zyngier
2024-02-14 18:32 ` Oliver Upton
2024-02-14 20:01 ` Marc Zyngier
2024-02-14 23:01 ` Oliver Upton [this message]
2024-02-15 9:44 ` Marc Zyngier
2024-02-13 9:32 ` [PATCH v2 08/23] KVM: arm64: vgic: Free LPI vgic_irq structs in an RCU-safe manner Oliver Upton
2024-02-13 9:32 ` [PATCH v2 09/23] KVM: arm64: vgic: Rely on RCU protection in vgic_get_lpi() Oliver Upton
2024-02-13 9:32 ` [PATCH v2 10/23] KVM: arm64: vgic: Ensure the irq refcount is nonzero when taking a ref Oliver Upton
2024-02-13 9:32 ` [PATCH v2 11/23] KVM: arm64: vgic: Don't acquire the lpi_list_lock in vgic_put_irq() Oliver Upton
2024-02-13 9:32 ` [PATCH v2 12/23] KVM: arm64: vgic-its: Lazily allocate LPI translation cache Oliver Upton
2024-02-13 9:32 ` [PATCH v2 13/23] KVM: arm64: vgic-its: Pick cache victim based on usage count Oliver Upton
2024-02-13 9:37 ` [PATCH v2 14/23] KVM: arm64: vgic-its: Protect cached vgic_irq pointers with RCU Oliver Upton
2024-02-13 9:39 ` [PATCH v2 15/23] KVM: arm64: vgic-its: Treat the LPI translation cache as an rculist Oliver Upton
2024-02-13 9:40 ` [PATCH v2 16/23] KVM: arm64: vgic-its: Rely on RCU to protect translation cache reads Oliver Upton
2024-02-13 9:40 ` [PATCH v2 17/23] KVM: selftests: Align with kernel's GIC definitions Oliver Upton
2024-02-13 9:40 ` [PATCH v2 18/23] KVM: selftests: Standardise layout of GIC frames Oliver Upton
2024-02-13 9:41 ` [PATCH v2 19/23] KVM: selftests: Add a minimal library for interacting with an ITS Oliver Upton
2024-02-14 17:32 ` Marc Zyngier
2024-02-14 19:00 ` Oliver Upton
2024-02-14 20:09 ` Marc Zyngier
2024-02-14 20:55 ` Oliver Upton
2024-02-14 21:06 ` Oliver Upton
2024-02-13 9:41 ` [PATCH v2 20/23] KVM: selftests: Add helper for enabling LPIs on a redistributor Oliver Upton
2024-02-13 9:42 ` [PATCH v2 21/23] KVM: selftests: Use MPIDR_HWID_BITMASK from cputype.h Oliver Upton
2024-02-13 9:43 ` [PATCH v2 22/23] KVM: selftests: Hack in support for aligned page allocations Oliver Upton
2024-02-13 9:43 ` [PATCH v2 23/23] KVM: selftests: Add stress test for LPI injection Oliver Upton
2024-02-13 20:12 ` [PATCH v2 00/23] KVM: arm64: Improvements to " Oliver Upton
2024-02-14 17:43 ` Marc Zyngier
2024-02-14 18:40 ` Oliver Upton
2024-02-15 15:37 ` Marc Zyngier
2024-02-15 20:15 ` Oliver Upton
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=Zc1GMFjvy_f1KsXr@linux.dev \
--to=oliver.upton@linux.dev \
--cc=james.morse@arm.com \
--cc=kvm@vger.kernel.org \
--cc=kvmarm@lists.linux.dev \
--cc=linux-kernel@vger.kernel.org \
--cc=maz@kernel.org \
--cc=suzuki.poulose@arm.com \
--cc=yuzenghui@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.