From: Alex Williamson <alex.williamson@redhat.com>
To: Auger Eric <eric.auger@redhat.com>
Cc: eauger@redhat.com, cprt@protonmail.com, iommu@lists.linux-foundation.org
Subject: Re: [PATCH] iommu/vt-d: Set ISA bridge reserved region as relaxable
Date: Thu, 12 Dec 2019 12:27:11 -0700 [thread overview]
Message-ID: <20191212122711.30e3b8ac@x1.home> (raw)
In-Reply-To: <e330865d-6f88-4537-72c6-f0ecc8252327@redhat.com>
On Thu, 12 Dec 2019 09:49:37 +0100
Auger Eric <eric.auger@redhat.com> wrote:
> Hi Alex,
>
> On 12/11/19 9:28 PM, Alex Williamson wrote:
> > Commit d850c2ee5fe2 ("iommu/vt-d: Expose ISA direct mapping region via
> > iommu_get_resv_regions") created a direct-mapped reserved memory region
> > in order to replace the static identity mapping of the ISA address
> > space, where the latter was then removed in commit df4f3c603aeb
> > ("iommu/vt-d: Remove static identity map code"). According to the
> > history of this code and the Kconfig option surrounding it, this direct
> > mapping exists for the benefit of legacy ISA drivers that are not
> > compatible with the DMA API.
> >
> > In conjuntion with commit 9b77e5c79840 ("vfio/type1: check dma map
> > request is within a valid iova range") this change introduced a
> > regression where the vfio IOMMU backend enforces reserved memory regions
> > per IOMMU group, preventing userspace from creating IOMMU mappings
> > conflicting with prescribed reserved regions. A necessary prerequisite
> > for the vfio change was the introduction of "relaxable" direct mappings
> > introduced by commit adfd37382090 ("iommu: Introduce
> > IOMMU_RESV_DIRECT_RELAXABLE reserved memory regions"). These relaxable
> > direct mappings provide the same identity mapping support in the default
> > domain, but also indicate that the reservation is software imposed and
> > may be relaxed under some conditions, such as device assignment.
> >
> > Convert the ISA bridge direct-mapped reserved region to relaxable to
> > reflect that the restriction is self imposed and need not be enforced
> > by drivers such as vfio.
> >
> > Fixes: d850c2ee5fe2 ("iommu/vt-d: Expose ISA direct mapping region via iommu_get_resv_regions")
> Maybe it is rather a fix of my patch, below, since above patch landed
> upstream before the IOMMU_RESV_DIRECT_RELAXABLE availability.
>
> Fixes: 1c5c59fbad20 ("iommu/vt-d: Differentiate relaxable and non
> relaxable RMRRs")
Sure, if you remember the ordering between these then that might be the
better option. I checked that they both entered the kernel for
v5.3-rc1 but didn't dig deeper than that.
Joerg, if you'd like a respin for that change let me know, otherwise
just swap my Fixes tag for the one Eric suggests.
> > Cc: stable@vger.kernel.org # v5.3+
> > Link: https://lore.kernel.org/linux-iommu/20191211082304.2d4fab45@x1.home
> > Reported-by: cprt <cprt@protonmail.com>
> > Tested-by: cprt <cprt@protonmail.com>
> > Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> Besides
> Reviewed-by: Eric Auger <eric.auger@redhat.com>
Thanks!
Alex
> > ---
> > drivers/iommu/intel-iommu.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> > index 0c8d81f56a30..6eb0dd7489a1 100644
> > --- a/drivers/iommu/intel-iommu.c
> > +++ b/drivers/iommu/intel-iommu.c
> > @@ -5737,7 +5737,7 @@ static void intel_iommu_get_resv_regions(struct device *device,
> >
> > if ((pdev->class >> 8) == PCI_CLASS_BRIDGE_ISA) {
> > reg = iommu_alloc_resv_region(0, 1UL << 24, 0,
> > - IOMMU_RESV_DIRECT);
> > + IOMMU_RESV_DIRECT_RELAXABLE);
> > if (reg)
> > list_add_tail(®->list, head);
> > }
> >
> > _______________________________________________
> > iommu mailing list
> > iommu@lists.linux-foundation.org
> > https://lists.linuxfoundation.org/mailman/listinfo/iommu
> >
_______________________________________________
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iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
next prev parent reply other threads:[~2019-12-12 19:27 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-11 20:28 [PATCH] iommu/vt-d: Set ISA bridge reserved region as relaxable Alex Williamson
2019-12-12 1:16 ` Lu Baolu
2019-12-12 8:49 ` Auger Eric
2019-12-12 19:27 ` Alex Williamson [this message]
2019-12-17 10:22 ` Joerg Roedel
2019-12-13 5:41 ` Jerry Snitselaar
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