From: "Xu, Quan" <quan.xu@intel.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: "Tian, Kevin" <kevin.tian@intel.com>, Keir Fraser <keir@xen.org>,
AndrewCooper <andrew.cooper3@citrix.com>,
"dario.faggioli@citrix.com" <dario.faggioli@citrix.com>,
"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
"Wu, Feng" <feng.wu@intel.com>
Subject: Re: [PATCH v4 01/10] vt-d: fix the IOMMU flush issue
Date: Thu, 12 May 2016 13:29:04 +0000 [thread overview]
Message-ID: <945CA011AD5F084CBEA3E851C0AB28894B8AD99D@SHSMSX101.ccr.corp.intel.com> (raw)
In-Reply-To: <5734608E02000078000EAD2B@prv-mh.provo.novell.com>
On May 12, 2016 4:53 PM, Jan Beulich <JBeulich@suse.com> wrote:
> >>> On 12.05.16 at 09:50, <quan.xu@intel.com> wrote:
> > On May 10, 2016 12:10 AM, Jan Beulich <JBeulich@suse.com> wrote:
> >> >>> On 06.05.16 at 10:54, <quan.xu@intel.com> wrote:
> >> > -static void intel_iommu_iotlb_flush(struct domain *d, unsigned
> >> > long gfn, unsigned int page_count)
> >> > +static void iommu_flush_iotlb_page(struct domain *d, unsigned long
> gfn,
> >> > + unsigned int page_count)
> >>
> >> The new name suggests just one page. Please use e.g.
> >> iommu_flush_iotlb_pages() instead.
> >>
> >
> > Make sense.
> >
> >> > {
> >> > - __intel_iommu_iotlb_flush(d, gfn, 1, page_count);
> >> > + iommu_flush_iotlb(d, gfn, 1, page_count);
> >> > }
> >>
> >> But of course the question is whether having this wrapper is useful
> >> in the first place,
> >
> >
> > This wrapper assumes the 'dma_old_pte_present' is '1', but in another
> > caller intel_iommu_map_page(), i.e.
> >
> >
> > intel_iommu_map_page()
> > {
> > ...
> > if ( !this_cpu(iommu_dont_flush_iotlb) )
> > iommu_flush_iotlb(d, gfn, dma_pte_present(old), 1);
> > ...
> > }
> >
> >
> > the 'dma_old_pte_present' is not sure.
>
> I'm sorry, but you're looking at this backwards: I suggested to remove the
> wrapper, not to move any check into iommu_flush_iotlb().
> Removing the wrapper simply means to move the passing of the hard coded 1
> into the current callers of that wrapper.
>
A little bit confused.
Check one thing, do the wrappers refer to iommu_flush_iotlb_page() and iommu_flush_iotlb_all() ?
If yes, we can't ignore another thing:
These two wrappers are also initialized for 2 .callbacks at the bottom of this file:
....
.iotlb_flush = iommu_flush_iotlb_pages,
.iotlb_flush_all = iommu_flush_iotlb_all,
....
> >> > @@ -1391,13 +1399,19 @@ int domain_context_mapping_one(
> >> > spin_unlock(&iommu->lock);
> >> >
> >> > /* Context entry was previously non-present (with domid 0). */
> >> > - if ( iommu_flush_context_device(iommu, 0, (((u16)bus) << 8) | devfn,
> >> > - DMA_CCMD_MASK_NOBIT, 1) )
> >> > - iommu_flush_write_buffer(iommu);
> >> > - else
> >> > + rc = iommu_flush_context_device(iommu, 0, (((u16)bus) << 8) |
> devfn,
> >> > + DMA_CCMD_MASK_NOBIT, 1);
> >> > +
> >> > + if ( !rc )
> >> > {
> >> > int flush_dev_iotlb = find_ats_dev_drhd(iommu) ? 1 : 0;
> >> > - iommu_flush_iotlb_dsi(iommu, 0, 1, flush_dev_iotlb);
> >> > + rc = iommu_flush_iotlb_dsi(iommu, 0, 1, flush_dev_iotlb);
> >>
> >> Please take the opportunity and add the missing blank line (between
> >> declaration(s) and statement(s) in cases like this.
> >>
> >> > + }
> >> > +
> >> > + if ( rc > 0 )
> >>
> >> Can iommu_flush_context_device() return a positive value? If so, the
> >> logic is now likely wrong. If not (which is what I assume) I'd like
> >> to suggest adding a respective ASSERT() (even if only to document the
> >> fact). Or alternatively this
> >> if() could move into the immediately preceding one.
> >
> > Check it again. iommu_flush_context_device() can return a positive value.
> > [...]
> > Could you tell me why the logic is now likely wrong? I will fix it first.
>
> With
>
> rc = iommu_flush_context_device(iommu, 0, (((u16)bus) << 8) | devfn,
> DMA_CCMD_MASK_NOBIT, 1);
>
> if ( !rc )
> {
> int flush_dev_iotlb = find_ats_dev_drhd(iommu) ? 1 : 0;
> rc = iommu_flush_iotlb_dsi(iommu, 0, 1, flush_dev_iotlb);
> }
>
> if ( rc > 0 )
> {
> iommu_flush_write_buffer(iommu);
> rc = 0;
> }
>
> it seems pretty clear that you won't call iommu_flush_iotlb_dsi() if
> iommu_flush_context_device() returned 1, which doesn't look like what is
> wanted at the first glance. But I may be wrong, hence the "likely" in my earlier
> reply.
>
Oh, this was on purpose.
If iommu_flush_context_device() returned 1, the iommu_flush_iotlb_dsi() returned 1 too.
As both flush_context_qi() and flush_iotlb_qi () are the same at the beginning of the functions.
One concern is if iommu_flush_context_device() is failed, then we won't call iommu_flush_iotlb_dsi(), which is not best effort to flush.
Quan
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next prev parent reply other threads:[~2016-05-12 13:29 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-06 8:54 [PATCH v4 00/10] Check VT-d Device-TLB flush error Quan Xu
2016-05-06 8:54 ` [PATCH v4 01/10] vt-d: fix the IOMMU flush issue Quan Xu
2016-05-09 16:09 ` Jan Beulich
2016-05-12 7:50 ` Xu, Quan
2016-05-12 8:53 ` Jan Beulich
2016-05-12 13:29 ` Xu, Quan [this message]
2016-05-12 13:37 ` Jan Beulich
2016-05-12 13:43 ` Xu, Quan
2016-05-06 8:54 ` [PATCH v4 02/10] IOMMU: handle IOMMU mapping and unmapping failures Quan Xu
2016-05-09 16:13 ` Jan Beulich
2016-05-10 3:41 ` Xu, Quan
2016-05-10 6:53 ` Jan Beulich
2016-05-10 7:53 ` Xu, Quan
2016-05-10 8:02 ` Jan Beulich
2016-05-10 8:20 ` Xu, Quan
2016-05-10 8:26 ` Jan Beulich
2016-05-12 14:28 ` Xu, Quan
2016-05-12 15:06 ` Jan Beulich
2016-05-13 8:04 ` Xu, Quan
2016-05-13 9:08 ` Jan Beulich
2016-05-13 9:20 ` Xu, Quan
2016-05-06 8:54 ` [PATCH v4 03/10] IOMMU/MMU: enhance the call trees of IOMMU unmapping and mapping Quan Xu
2016-05-10 8:44 ` Jan Beulich
2016-05-10 14:45 ` George Dunlap
2016-05-10 14:59 ` George Dunlap
2016-05-11 2:26 ` Xu, Quan
2016-05-11 8:45 ` George Dunlap
2016-05-11 8:58 ` Xu, Quan
2016-05-10 15:02 ` Jan Beulich
2016-05-11 2:29 ` Xu, Quan
2016-05-11 3:39 ` Xu, Quan
2016-05-11 7:02 ` Jan Beulich
2016-05-06 8:54 ` [PATCH v4 04/10] vt-d: propagate IOMMU Device-TLB flush error up to IOMMU unmapping Quan Xu
2016-05-10 8:50 ` Jan Beulich
2016-05-11 3:49 ` Xu, Quan
2016-05-06 8:54 ` [PATCH v4 05/10] vt-d: propagate IOMMU Device-TLB flush error up to IOMMU mapping Quan Xu
2016-05-06 8:54 ` [PATCH v4 06/10] IOMMU/MMU: propagate IOMMU Device-TLB flush error up to iommu_iotlb_flush{, _all} (top level ones) Quan Xu
2016-05-10 9:04 ` Jan Beulich
2016-05-11 5:52 ` Xu, Quan
2016-05-06 8:54 ` [PATCH v4 07/10] IOMMU: propagate IOMMU Device-TLB flush error up to iommu_iotlb_flush{, _all} (leaf ones) Quan Xu
2016-05-10 9:06 ` Jan Beulich
2016-05-11 6:47 ` Xu, Quan
2016-05-11 7:06 ` Jan Beulich
2016-05-11 7:12 ` Xu, Quan
2016-05-11 7:16 ` Jan Beulich
2016-05-11 7:20 ` Xu, Quan
2016-05-11 7:37 ` Jan Beulich
2016-05-06 8:54 ` [PATCH v4 08/10] vt-d/ept: propagate IOMMU Device-TLB flush error up to EPT update Quan Xu
2016-05-10 9:09 ` Jan Beulich
2016-05-10 14:58 ` George Dunlap
2016-05-10 15:04 ` Jan Beulich
2016-05-11 7:25 ` Xu, Quan
2016-05-06 8:54 ` [PATCH v4 09/10] IOMMU: propagate IOMMU Device-TLB flush error up to IOMMU suspending Quan Xu
2016-05-10 9:24 ` Jan Beulich
2016-05-13 3:39 ` Xu, Quan
2016-05-13 6:16 ` Jan Beulich
2016-05-13 6:27 ` Xu, Quan
2016-05-06 8:54 ` [PATCH v4 10/10] vt-d: propagate error up to ME phantom function mapping and unmapping Quan Xu
2016-05-10 9:29 ` Jan Beulich
2016-05-11 8:35 ` Xu, Quan
2016-05-11 9:07 ` Jan Beulich
2016-05-12 5:16 ` Xu, Quan
2016-05-12 8:44 ` Jan Beulich
2016-05-12 9:02 ` Xu, Quan
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