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>,
George Dunlap <george.dunlap@eu.citrix.com>,
Liu Jinsong <jinsong.liu@alibaba-inc.com>,
Dario Faggioli <dario.faggioli@citrix.com>,
"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
Jun Nakajima <jun.nakajima@intel.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Keir Fraser <keir@xen.org>
Subject: Re: [PATCH 1/2] IOMMU/MMU: Adjust top level functions for VT-d Device-TLB flush error.
Date: Tue, 29 Mar 2016 01:20:35 -0600 [thread overview]
Message-ID: <56FA48E302000078000E0B40@prv-mh.provo.novell.com> (raw)
In-Reply-To: <945CA011AD5F084CBEA3E851C0AB28894B86D176@SHSMSX101.ccr.corp.intel.com>
>>> On 28.03.16 at 05:33, <quan.xu@intel.com> wrote:
> On March 18, 2016 1:15am, <JBeulich@suse.com> wrote:
>> >>> On 17.03.16 at 07:54, <quan.xu@intel.com> wrote:
>> > --- a/xen/common/grant_table.c
>> > +++ b/xen/common/grant_table.c
>> > @@ -932,8 +932,9 @@ __gnttab_map_grant_ref(
>> > {
>> > nr_gets++;
>> > (void)get_page(pg, rd);
>> > - if ( !(op->flags & GNTMAP_readonly) )
>> > - get_page_type(pg, PGT_writable_page);
>> > + if ( !(op->flags & GNTMAP_readonly) &&
>> > + !get_page_type(pg, PGT_writable_page) )
>> > + goto could_not_pin;
>>
>> This needs explanation, as it doesn't look related to what your actual goal is: If
>> an error was possible here, I think this would be a security issue. However, as
>> also kind of documented by the explicitly ignored return value from get_page(),
>> it is my understanding there here we only obtain an _extra_ reference.
>>
>
> For this point, I inferred from:
> map_vcpu_info()
> {
> ...
> if ( !get_page_type(page, PGT_writable_page) )
> {
> put_page(page);
> return -EINVAL;
> }
> ...
> }
> , then for get_page_type(), I think the return value:
> 0 -- error,
> 1-- right.
>
> So if get_page_type() is failed, we should goto could_not_pin.
Did you read my reply at all? The explanation I'm expecting here is
why error checking is all of the sudden needed _at all_.
> btw, there is another issue in the call path:
> iommu_{,un}map_page() -- __get_page_type() -- get_page_type()---
>
>
> I tried to return iommu_{,un}map_page() error code in __get_page_type(), is
> it right?
If the operation got fully rolled back - yes. Whether fully rolling back
is feasible there though is - see the respective discussion - an open
question.
>> > --- a/xen/drivers/passthrough/x86/iommu.c
>> > +++ b/xen/drivers/passthrough/x86/iommu.c
>> > @@ -104,7 +104,11 @@ int arch_iommu_populate_page_table(struct
>> domain *d)
>> > this_cpu(iommu_dont_flush_iotlb) = 0;
>> >
>> > if ( !rc )
>> > - iommu_iotlb_flush_all(d);
>> > + {
>> > + rc = iommu_iotlb_flush_all(d);
>> > + if ( rc )
>> > + iommu_teardown(d);
>> > + }
>> > else if ( rc != -ERESTART )
>> > iommu_teardown(d);
>>
>> Why can't you just use the existing call to iommu_teardown(), by simply
> deleting
>> the "else"?
>>
>
> Just check it, could I modify it as below:
> --- a/xen/drivers/passthrough/x86/iommu.c
> +++ b/xen/drivers/passthrough/x86/iommu.c
> @@ -105,7 +105,8 @@ int arch_iommu_populate_page_table(struct domain *d)
>
> if ( !rc )
> iommu_iotlb_flush_all(d);
> - else if ( rc != -ERESTART )
> +
> + if ( rc != -ERESTART )
> iommu_teardown(d);
Clearly not - not only are you losing the return value of
iommu_iotlb_flush_all() now, you would then also call
iommu_teardown() in the "success" case. My comment was
related to code structure, yet you seem to have taken it
literally.
Jan
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next prev parent reply other threads:[~2016-03-29 7:20 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-17 6:54 [PATCH 0/2] Check VT-d Device-TLB flush error 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 [this message]
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
2016-04-12 1:09 ` Xu, Quan
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