linux-kernel - Re: [KVM PATCH v3 2/2] kvm: add support for irqfd via eventfd-notification interface

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]

Date:	Thu, 30 Apr 2009 16:07:08 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Gregory Haskins <ghaskins@...ell.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, avi@...hat.com,
	davidel@...ilserver.org
Subject: Re: [KVM PATCH v3 2/2] kvm: add support for irqfd via
	eventfd-notification interface

On Mon, Apr 27, 2009 at 02:33:34PM -0400, Gregory Haskins wrote:
> This allows an eventfd to be registered as an irq source with a guest.  Any
> signaling operation on the eventfd (via userspace or kernel) will inject
> the registered GSI at the next available window.
> 
> Signed-off-by: Gregory Haskins <ghaskins@...ell.com>

If we ever want to use this with e.g. MSI-X emulation in guest, and want
to be stricly compliant to MSI-X, we'll need a way for guest to mask
interrupts, and for host to report that a masked interrupt is pending.
Ideally, all this will be doable with a couple of mmapped pages to avoid
vmexits/system calls.

> +static void
> +irqfd_inject(struct work_struct *work)
> +{
> +	struct _irqfd *irqfd = container_of(work, struct _irqfd, work);
> +	struct kvm *kvm = irqfd->kvm;
> +
> +	mutex_lock(&kvm->lock);
> +	kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 1);
> +	kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 0);
> +	mutex_unlock(&kvm->lock);

This will do weird stuff (deliver the irq twice) if the irq is
MSI/MSI-X. I know this was discussed already and is a temporary
shortcut, but maybe add a comment that we really want kvm_toggle_irq,
so that we won't forget?

> +}
> +

-- 
MST
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/