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Re: [Qemu-devel] [RFC][PATCH 12/45] msi: Introduce MSIRoutingCache
From: |
Jan Kiszka |
Subject: |
Re: [Qemu-devel] [RFC][PATCH 12/45] msi: Introduce MSIRoutingCache |
Date: |
Mon, 17 Oct 2011 21:23:56 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
On 2011-10-17 17:43, Michael S. Tsirkin wrote:
> On Mon, Oct 17, 2011 at 11:27:46AM +0200, Jan Kiszka wrote:
>> This cache will help us implementing KVM in-kernel irqchip support
>> without spreading hooks all over the place.
>>
>> KVM requires us to register it first and then deliver it by raising a
>> pseudo IRQ line returned on registration. While this could be changed
>> for QEMU-originated MSI messages by adding direct MSI injection, we will
>> still need this translation for irqfd-originated messages. The
>> MSIRoutingCache will allow to track those registrations and update them
>> lazily before the actual delivery. This avoid having to track MSI
>> vectors at device level (like qemu-kvm currently does).
>>
>> Signed-off-by: Jan Kiszka <address@hidden>
>
> So if many devices are added, exhausting the number of GSIs supported,
> we get terrible performance intead of simply failing outright.
>
> To me, this looks more like a bug than a feature ...
If that ever turns out to be a bottleneck, failing looks like the worst
we can do. Reporting excessive cache flushes would make some sense and
could still be added.
Jan
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Re: [Qemu-devel] [RFC][PATCH 12/45] msi: Introduce MSIRoutingCache, Michael S. Tsirkin, 2011/10/17
- Re: [Qemu-devel] [RFC][PATCH 12/45] msi: Introduce MSIRoutingCache,
Jan Kiszka <=
[Qemu-devel] [RFC][PATCH 03/45] msi: Use msi/msix_present more consistently, Jan Kiszka, 2011/10/17
[Qemu-devel] [RFC][PATCH 19/45] qemu-kvm: Factor out kvm_msi_irqfd_set, Jan Kiszka, 2011/10/17
[Qemu-devel] [RFC][PATCH 21/45] qemu-kvm: msix: Don't fire notifier spuriously on set/unset, Jan Kiszka, 2011/10/17
[Qemu-devel] [RFC][PATCH 02/45] msi: Guard msi_reset with msi_present, Jan Kiszka, 2011/10/17
[Qemu-devel] [RFC][PATCH 22/45] qemu-kvm: msix: Fire mask notifier on global mask changes, Jan Kiszka, 2011/10/17