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From: "Jan Beulich" <JBeulich@suse.com>
To: Quan Xu <quan.xu@intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>, Feng Wu <feng.wu@intel.com>,
	Jun Nakajima <jun.nakajima@intel.com>,
	George Dunlap <george.dunlap@eu.citrix.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	DarioFaggioli <dario.faggioli@citrix.com>,
	"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
	Julien Grall <julien.grall@arm.com>,
	StefanoStabellini <stefano.stabellini@citrix.com>,
	Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
	Keir Fraser <keir@xen.org>
Subject: Re: [PATCH 2/2] IOMMU/MMU: Adjust low level functions for VT-d Device-TLB flush error.
Date: Mon, 11 Apr 2016 10:34:42 -0600	[thread overview]
Message-ID: <570BE03202000078000E63FA@prv-mh.provo.novell.com> (raw)
In-Reply-To: <945CA011AD5F084CBEA3E851C0AB28894B8881BA@SHSMSX101.ccr.corp.intel.com>

>>> On 11.04.16 at 05:27, <quan.xu@intel.com> wrote:
> On April 11, 2016 11:10am, <quan.xu@intel.com> wrote:
>> On March 29, 2016 3:37pm, Jan Beulich <JBeulich@suse.com> wrote:
>> > >>> On 25.03.16 at 10:27, <quan.xu@intel.com> wrote:
>> > > On March 18, 2016 6:20pm, <JBeulich@suse.com> wrote:
>> > >> >>> On 17.03.16 at 07:54, <quan.xu@intel.com> wrote:
>> > >> > --- a/xen/drivers/passthrough/iommu.c
>> > >> > +++ b/xen/drivers/passthrough/iommu.c
>> > >> > @@ -554,11 +555,24 @@ static void iommu_flush_all(void)
>> > >> >          iommu = drhd->iommu;
>> > >> >          iommu_flush_context_global(iommu, 0);
>> > >> >          flush_dev_iotlb = find_ats_dev_drhd(iommu) ? 1 : 0;
>> > >> > -        iommu_flush_iotlb_global(iommu, 0, flush_dev_iotlb);
>> > >> > +        rc = iommu_flush_iotlb_global(iommu, 0,
>> > >> > + flush_dev_iotlb);
>> > >> > +
>> > >> > +        if ( rc > 0 )
>> > >> > +        {
>> > >> > +            iommu_flush_write_buffer(iommu);
>> > >>
>> > >> Why is this needed all of the sudden?
>> > >
>> > > As there may be multiple IOMMUs. .e.g, there are 2 IOMMUs in my
>> > > machine, and I can find the following log message:
>> > > """
>> > > (XEN) Intel VT-d iommu 0 supported page sizes: 4kB, 2MB, 1GB.
>> > > (XEN) Intel VT-d iommu 1 supported page sizes: 4kB, 2MB, 1GB.
>> > > """
>> > > __iiuc__, iommu_flush_write_buffer() is per IOMMU, so It should be
>> > > called to flush every IOMMU.
>> >
>> > For one what you say suggests that right now this is being done for
>> > some (one?) IOMMU(s), which I don't see being the case. And then what
>> > you say _still_ doesn't say _why_ this is now needed all of the
>> > sudden. If, in the course of doing your re-work here, you find
>> > pre-existing issues with the code, please split the necessary fixes
>> > out of your re-work and submit them separately with proper explanations in
>> their commit messages.
>> >
>> 
>> I find out it is no need modification for this function.
> Sorry, this modification refers to as:
> "
> +        if ( rc > 0 )
> +        {
> +            iommu_flush_write_buffer(iommu);
> +            rc = 0;
> +        }
> "
> 
> at least errors need to be propagated.

How does error propagation correlate with suddenly calling
iommu_flush_write_buffer()?

Jan


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  reply	other threads:[~2016-04-11 16:34 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-17  6:54 [PATCH 0/2] Check " Quan Xu
2016-03-17  6:54 ` [PATCH 1/2] IOMMU/MMU: Adjust top level functions for " Quan Xu
2016-03-17  7:32   ` Tian, Kevin
2016-03-17  7:58     ` Jan Beulich
2016-03-17  8:00       ` Tian, Kevin
2016-03-17 12:30   ` George Dunlap
2016-03-17 12:33     ` George Dunlap
2016-03-18  3:19       ` Xu, Quan
2016-03-18  8:09         ` Jan Beulich
2016-03-24  6:45           ` Xu, Quan
2016-03-18  7:54     ` Xu, Quan
2016-03-18  8:19       ` Jan Beulich
2016-03-18  9:09         ` Xu, Quan
2016-03-18  9:29           ` Jan Beulich
2016-03-18  9:38             ` Dario Faggioli
2016-03-18  9:48               ` Jan Beulich
2016-03-21  6:18                 ` Tian, Kevin
2016-03-21 12:22                   ` Jan Beulich
2016-03-24  9:02                 ` Xu, Quan
2016-03-24  9:58                   ` Jan Beulich
2016-03-24 14:12                     ` Xu, Quan
2016-03-24 14:37                       ` Jan Beulich
2016-03-17 17:14   ` Jan Beulich
2016-03-28  3:33     ` Xu, Quan
2016-03-29  7:20       ` Jan Beulich
2016-03-30  2:28         ` Xu, Quan
2016-03-30  2:35           ` Xu, Quan
2016-03-30  8:05           ` Jan Beulich
2016-03-17  6:54 ` [PATCH 2/2] IOMMU/MMU: Adjust low " Quan Xu
2016-03-17  7:37   ` Tian, Kevin
2016-03-18  2:30     ` Xu, Quan
2016-03-18  8:06       ` Jan Beulich
2016-03-21  5:01         ` Tian, Kevin
2016-03-17 15:31   ` George Dunlap
2016-03-18  6:57     ` Xu, Quan
2016-03-18 10:20   ` Jan Beulich
2016-03-25  9:27     ` Xu, Quan
2016-03-29  7:36       ` Jan Beulich
2016-04-11  3:09         ` Xu, Quan
2016-04-11  3:27           ` Xu, Quan
2016-04-11 16:34             ` Jan Beulich [this message]
2016-04-12  1:09               ` Xu, Quan

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