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From: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: "eric.auger@redhat.com" <eric.auger@redhat.com>,
	"pmorel@linux.vnet.ibm.com" <pmorel@linux.vnet.ibm.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	Linuxarm <linuxarm@huawei.com>,
	"John Garry" <john.garry@huawei.com>,
	"xuwei (O)" <xuwei5@huawei.com>, Joerg Roedel <joro@8bytes.org>,
	David Woodhouse <dwmw2@infradead.org>
Subject: RE: [PATCH v6 0/7] vfio/type1: Add support for valid iova list management
Date: Wed, 6 Jun 2018 06:52:08 +0000	[thread overview]
Message-ID: <5FC3163CFD30C246ABAA99954A238FA8386F783C@FRAEML521-MBX.china.huawei.com> (raw)
In-Reply-To: <20180605110304.33e14b0d@w520.home>



> -----Original Message-----
> From: Alex Williamson [mailto:alex.williamson@redhat.com]
> Sent: 05 June 2018 18:03
> To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>
> Cc: eric.auger@redhat.com; pmorel@linux.vnet.ibm.com;
> kvm@vger.kernel.org; linux-kernel@vger.kernel.org; iommu@lists.linux-
> foundation.org; Linuxarm <linuxarm@huawei.com>; John Garry
> <john.garry@huawei.com>; xuwei (O) <xuwei5@huawei.com>; Joerg Roedel
> <joro@8bytes.org>; David Woodhouse <dwmw2@infradead.org>
> Subject: Re: [PATCH v6 0/7] vfio/type1: Add support for valid iova list
> management
> 
> [Cc +dwmw2]
> 
> On Fri, 25 May 2018 14:54:08 -0600
> Alex Williamson <alex.williamson@redhat.com> wrote:
> 
> > On Fri, 25 May 2018 08:45:36 +0000
> > Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>
> wrote:
> >
> > > Yes, the above changes related to list empty cases looks fine to me.
> >
> > Thanks Shameer, applied to my next branch with the discussed fixes for
> > v4.18 (modulo patch 4/7 which Joerg already pushed for v4.17).  Thanks,
> 
> Hi Shameer,
> 
> We're still hitting issues with this.  VT-d marks reserved regions for
> any RMRR ranges, which are IOVA ranges that the BIOS requests to be
> identity mapped for a device.  These are indicated by these sorts of
> log entries on boot:
> 
>  DMAR: Setting RMRR:
>  DMAR: Setting identity map for device 0000:00:02.0 [0xbf800000 - 0xcf9fffff]
>  DMAR: Setting identity map for device 0000:00:1a.0 [0xbe8d1000 - 0xbe8dffff]
>  DMAR: Setting identity map for device 0000:00:1d.0 [0xbe8d1000 - 0xbe8dffff]
> 
> So while for an unaffected device, I see very usable ranges for QEMU,
> such as:
> 
> 	00: 0000000000000000 - 00000000fedfffff
> 	01: 00000000fef00000 - 01ffffffffffffff
> 
> If I try to assign the previously assignable 00:02.0 IGD graphics
> device, I get:
> 
> 	00: 0000000000000000 - 00000000bf7fffff
> 	01: 00000000cfa00000 - 00000000fedfffff
> 	02: 00000000fef00000 - 01ffffffffffffff
> 
> And we get a fault when QEMU tries the following mapping:
> 
> vfio_dma_map(0x55f790421a20, 0x100000, 0xbff00000, 0x7ff163f00000)
> 
> bff00000 clearly extends into the gap starting at bf800000.  VT-d is
> rather split-brained about RMRRs, typically we'd exclude devices from
> assignment at all for relying on RMRRs and these reserved ranges
> would be a welcome mechanism to avoid conflicts with those ranges, but
> for RMRR ranges covering IGD and USB devices we've decided that we
> don't need to honor the RMRR (see device_is_rmrr_locked()), but it's
> still listed as a reserved range and bites us here.

Ah..:(. This looks similar to the pci window range reporting issue faced in
the arm world. I see the RFC you have sent out to ignore these "known" 
RMRRs. Hope we will be able to resolve this soon.

Thanks,
Shameer

> Unless we can get VT-d to exclude RMRRs from reserved regions where
> we've already seen fit to allow the devices to participate in the IOMMU
> API, this would introduce a functional regression for assignment of
> these devices.  David, should we skip GFX and USB devices with RMRRs in
> intel_iommu_get_resv_regions() just as we do in
> device_is_rmrr_locked()?  Thanks,
> 
> Alex

  reply	other threads:[~2018-06-06  6:52 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-18 11:40 Shameer Kolothum
2018-04-18 11:40 ` [PATCH v6 1/7] vfio/type1: Introduce iova list and add iommu aperture validity check Shameer Kolothum
2018-04-18 11:40 ` [PATCH v6 2/7] vfio/type1: Check reserve region conflict and update iova list Shameer Kolothum
2018-04-18 11:40 ` [PATCH v6 3/7] vfio/type1: Update iova list on detach Shameer Kolothum
2018-04-18 11:40 ` [PATCH v6 4/7] iommu/dma: Move PCI window region reservation back into dma specific path Shameer Kolothum
2018-04-24 13:16   ` Shameerali Kolothum Thodi
2018-04-30 16:10     ` Alex Williamson
2018-05-03 13:16   ` Joerg Roedel
2018-04-18 11:40 ` [PATCH v6 5/7] vfio/type1: check dma map request is within a valid iova range Shameer Kolothum
2018-04-18 11:40 ` [PATCH v6 6/7] vfio/type1: Add IOVA range capability support Shameer Kolothum
2018-04-18 11:40 ` [PATCH v6 7/7] vfio/type1: remove duplicate retrieval of reserved regions Shameer Kolothum
2018-05-24 18:20 ` [PATCH v6 0/7] vfio/type1: Add support for valid iova list management Alex Williamson
2018-05-25  8:45   ` Shameerali Kolothum Thodi
2018-05-25 20:54     ` Alex Williamson
2018-06-05 17:03       ` Alex Williamson
2018-06-06  6:52         ` Shameerali Kolothum Thodi [this message]
2018-06-07 15:05           ` Alex Williamson

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