linux-kernel - Re: [PATCH V4] xen: privcmd: Add support for irqfd

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]

Message-ID: <20230816062901.dkpzhhimnjf35jqy@vireshk-i7>
Date:   Wed, 16 Aug 2023 11:59:01 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>
Cc:     Vincent Guittot <vincent.guittot@...aro.org>,
        Alex Bennée <alex.bennee@...aro.org>,
        stratos-dev@...lists.linaro.org,
        Erik Schilling <erik.schilling@...aro.org>,
        Manos Pitsidianakis <manos.pitsidianakis@...aro.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4] xen: privcmd: Add support for irqfd

On 25-07-23, 16:27, Viresh Kumar wrote:
> Xen provides support for injecting interrupts to the guests via the
> HYPERVISOR_dm_op() hypercall. The same is used by the Virtio based
> device backend implementations, in an inefficient manner currently.
> 
> Generally, the Virtio backends are implemented to work with the Eventfd
> based mechanism. In order to make such backends work with Xen, another
> software layer needs to poll the Eventfds and raise an interrupt to the
> guest using the Xen based mechanism. This results in an extra context
> switch.
> 
> This is not a new problem in Linux though. It is present with other
> hypervisors like KVM, etc. as well. The generic solution implemented in
> the kernel for them is to provide an IOCTL call to pass the interrupt
> details and eventfd, which lets the kernel take care of polling the
> eventfd and raising of the interrupt, instead of handling this in user
> space (which involves an extra context switch).
> 
> This patch adds support to inject a specific interrupt to guest using
> the eventfd mechanism, by preventing the extra context switch.
> 
> Inspired by existing implementations for KVM, etc..
> 
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
> V3->V4
> - Drop the imported definitions to hvm/dm_op.h.
> - Make the caller pass a pointer to pre-filled "struct xen_dm_op" instance and
>   get rid of irq and level fields.
> - Enable the irqfd feature under a new Kconfig entry.

Ping.

-- 
viresh