From: Sheng Yang <sheng@linux.intel.com>
To: Avi Kivity <avi@redhat.com>
Cc: kvm@vger.kernel.org, "Han, Weidong" <weidong.han@intel.com>,
"Kay, Allen M" <allen.m.kay@intel.com>
Subject: Re: [PATCH 4/4] KVM: x86: Enable MSI for assigned device
Date: Wed, 8 Oct 2008 10:55:48 +0800 [thread overview]
Message-ID: <200810081055.48842.sheng@linux.intel.com> (raw)
In-Reply-To: <48EB6751.9080901@redhat.com>
On Tuesday 07 October 2008 21:42:41 Avi Kivity wrote:
> Sheng Yang wrote:
> > Seems we needn't tell userspace if MSI can be enabled. It's determined
> > mostly by the device, and pci_enable_msi() checked that.
> >
> > So I think QEmu can expose MSI capability if the device got it. If it's
> > fail to be enabled, just fall back to IRQ and return error to QEmu is
> > enough, of course, QEmu should set MSI enable bit after kernel space
> > done.
>
> Do we need to add the additional condition, "and if the host kernel
> supports it"?
Well, for VT-d, it's impossible because CONFIG_DMAR depends on
CONFIG_PCI_MSI...
And for non-VT-d(I don't know about PV or AMD IOMMU), from 2.6.18, MSI support
have been added, before KVM merged. And we also got
ifndef CONFIG_PCI_MSI, pci_enable_msi return -1.
So we can still fall back to IRQ without error.
How do you think?
--
regards
Yang, Sheng
next prev parent reply other threads:[~2008-10-08 2:58 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-09-26 5:17 [PATCH 4/4] KVM: x86: Enable MSI for assigned device Sheng Yang
2008-10-05 10:27 ` Avi Kivity
2008-10-06 3:36 ` Yang, Sheng
2008-10-07 5:59 ` Sheng Yang
2008-10-07 13:42 ` Avi Kivity
2008-10-08 2:55 ` Sheng Yang [this message]
-- strict thread matches above, loose matches on Subject: below --
2008-10-07 6:09 Sheng Yang
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