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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>,
	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, 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: Thu, 17 Mar 2016 11:14:54 -0600	[thread overview]
Message-ID: <56EAF41E02000078000DE065@prv-mh.provo.novell.com> (raw)
In-Reply-To: <1458197676-60696-2-git-send-email-quan.xu@intel.com>

>>> On 17.03.16 at 07:54, <quan.xu@intel.com> wrote:
> @@ -53,11 +55,21 @@ static int device_power_down(void)
>  
>      ioapic_suspend();
>  
> -    iommu_suspend();
> +    err = iommu_suspend();
> +    if ( err )
> +        goto iommu_suspend_error;
>  
>      lapic_suspend();
>  
>      return 0;
> +
> +iommu_suspend_error:

Labels indented by at least one space please.

> --- a/xen/arch/x86/mm/p2m-ept.c
> +++ b/xen/arch/x86/mm/p2m-ept.c
> @@ -830,7 +830,15 @@ out:
>          {
>              if ( iommu_flags )
>                  for ( i = 0; i < (1 << order); i++ )
> -                    iommu_map_page(d, gfn + i, mfn_x(mfn) + i, iommu_flags);
> +                {
> +                    rc = iommu_map_page(d, gfn + i, mfn_x(mfn) + i, iommu_flags);
> +                    if ( rc )
> +                    {
> +                        while ( i-- > 0 )
> +                            iommu_unmap_page(d, gfn + i);
> +                        break;
> +                    }
> +                }
>              else
>                  for ( i = 0; i < (1 << order); i++ )
>                      iommu_unmap_page(d, gfn + i);

Earlier on in the PV mm code you also checked iommu_unmap_page()'s
return code - why not here (and also in p2m-pt.c)?

Also I'm quite unhappy about the inconsistent state you leave things
in: You unmap from the IOMMU, return an error, but leave the EPT
entry in place.

> --- 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.

> --- a/xen/common/memory.c
> +++ b/xen/common/memory.c
> @@ -678,8 +678,9 @@ static int xenmem_add_to_physmap(struct domain *d,
>      if ( need_iommu(d) )
>      {
>          this_cpu(iommu_dont_flush_iotlb) = 0;
> -        iommu_iotlb_flush(d, xatp->idx - done, done);
> -        iommu_iotlb_flush(d, xatp->gpfn - done, done);
> +        rc = iommu_iotlb_flush(d, xatp->idx - done, done);
> +        if ( !rc )
> +            rc = iommu_iotlb_flush(d, xatp->gpfn - done, done);
>      }

And the pattern repeats - you now return an error, but you don't
roll back the now failed operation. But wait - maybe that intended:
Are you meaning to crash the guest in such cases (somewhere
deep in the flush code)? If so, I think that's fine, but you
absolutely would need to say so in the commit message.

> --- 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"?

Jan


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  parent reply	other threads:[~2016-03-17 17:14 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 [this message]
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
2016-04-12  1:09               ` Xu, Quan

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