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From: "Tian, Kevin" <kevin.tian@intel.com>
To: Paul Durrant <Paul.Durrant@citrix.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Cc: Jan Beulich <jbeulich@suse.com>
Subject: Re: [PATCH v5 07/15] iommu: track reserved ranges using a rangeset
Date: Tue, 7 Aug 2018 08:23:54 +0000	[thread overview]
Message-ID: <AADFC41AFE54684AB9EE6CBC0274A5D1912AE8F9@SHSMSX101.ccr.corp.intel.com> (raw)
In-Reply-To: <53062aabdb904f26adf33f657a94788f@AMSPEX02CL03.citrite.net>

> From: Paul Durrant [mailto:Paul.Durrant@citrix.com]
> Sent: Tuesday, August 7, 2018 4:16 PM
> 
> > -----Original Message-----
> > From: Tian, Kevin [mailto:kevin.tian@intel.com]
> > Sent: 07 August 2018 04:04
> > To: Paul Durrant <Paul.Durrant@citrix.com>; xen-
> devel@lists.xenproject.org
> > Cc: Jan Beulich <jbeulich@suse.com>
> > Subject: RE: [PATCH v5 07/15] iommu: track reserved ranges using a
> rangeset
> >
> > > From: Paul Durrant [mailto:paul.durrant@citrix.com]
> > > Sent: Saturday, August 4, 2018 1:22 AM
> > >
> > > Ranges that should be considered reserved in the IOMMU are not
> > > necessarily
> > > limited to RMRRs. If iommu_inclusive_mapping is set then any frame
> > > number
> > > falling within an E820 reserved region should also be considered as
> > > reserved in the IOMMU.
> >
> > I don't think it is a good extension. RMRR by definition requires
> > identity mapping in IOMMU page table, thus must be also reserved
> > in bfn address space (to avoid being used for other purpose).
> > Normal E820 reserved regions have no such requirement. Guest
> > can use same bfn location for any purpose. I'm not sure why we
> > want to add more limitations here.
> 
> Have you tried booting an average Intel based server without identity
> mapped E820 reserved regions? Good luck with that, because I think about
> half the servers on the planet will wedge up if you only give them RMRRs.
> My Dell R730 certainly will and I'd hazard a guess that any other Dell box
> we have with an iDRAC will too.
> Note the behaviour is predicated on 'iommu_inclusive_mapping' being set
> so if you feel lucky then you can turn it off :-)
> 

I know that fact... looks I misunderstood the patch - I thought you
blindly add all reserved regions in this patch bypassing the existing
control from inclusive_mapping. Now re-read the description and
code you are just giving background :-)

Thanks
Kevin

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  reply	other threads:[~2018-08-07  8:24 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-03 17:22 [PATCH v5 00/15] paravirtual IOMMU interface Paul Durrant
2018-08-03 17:22 ` [PATCH v5 01/15] iommu: turn need_iommu back into a boolean Paul Durrant
2018-08-08 13:39   ` Jan Beulich
2018-08-08 13:56     ` Paul Durrant
2018-08-03 17:22 ` [PATCH v5 02/15] iommu: introduce the concept of BFN Paul Durrant
2018-08-07  2:38   ` Tian, Kevin
2018-08-07  7:59     ` Paul Durrant
2018-08-07  8:26       ` Tian, Kevin
2018-08-03 17:22 ` [PATCH v5 03/15] iommu: make use of type-safe BFN and MFN in exported functions Paul Durrant
2018-08-07  2:45   ` Tian, Kevin
2018-08-03 17:22 ` [PATCH v5 04/15] iommu: push use of type-safe BFN and MFN into iommu_ops Paul Durrant
2018-08-07  2:49   ` Tian, Kevin
2018-08-03 17:22 ` [PATCH v5 05/15] iommu: don't domain_crash() inside iommu_map/unmap_page() Paul Durrant
2018-08-07  2:55   ` Tian, Kevin
2018-08-07  8:05     ` Paul Durrant
2018-08-07  8:23       ` Jan Beulich
2018-08-03 17:22 ` [PATCH v5 06/15] public / x86: introduce __HYPERCALL_iommu_op Paul Durrant
2018-08-07  3:00   ` Tian, Kevin
2018-08-07  8:10     ` Paul Durrant
2018-08-07  8:25       ` Jan Beulich
2018-08-17 21:10   ` Daniel De Graaf
2018-08-03 17:22 ` [PATCH v5 07/15] iommu: track reserved ranges using a rangeset Paul Durrant
2018-08-07  3:04   ` Tian, Kevin
2018-08-07  8:16     ` Paul Durrant
2018-08-07  8:23       ` Tian, Kevin [this message]
2018-08-03 17:22 ` [PATCH v5 08/15] x86: add iommu_op to query reserved ranges Paul Durrant
2018-08-03 17:22 ` [PATCH v5 09/15] vtd: add lookup_page method to iommu_ops Paul Durrant
2018-08-07  3:25   ` Tian, Kevin
2018-08-07  8:21     ` Paul Durrant
2018-08-07  8:29       ` Jan Beulich
2018-08-07  8:32         ` Tian, Kevin
2018-08-07  8:37           ` Paul Durrant
2018-08-07  8:48             ` Tian, Kevin
2018-08-07  8:56               ` Paul Durrant
2018-08-07  9:03                 ` Tian, Kevin
2018-08-07  9:07                   ` Paul Durrant
2018-08-07  8:31       ` Tian, Kevin
2018-08-07  8:35         ` Paul Durrant
2018-08-07  8:47           ` Tian, Kevin
2018-08-03 17:22 ` [PATCH v5 10/15] mm / iommu: include need_iommu() test in iommu_use_hap_pt() Paul Durrant
2018-08-07  3:32   ` Tian, Kevin
2018-08-03 17:22 ` [PATCH v5 11/15] mm / iommu: split need_iommu() into has_iommu_pt() and sync_iommu_pt() Paul Durrant
2018-08-03 18:18   ` Razvan Cojocaru
2018-08-07  3:41   ` Tian, Kevin
2018-08-07  8:24     ` Paul Durrant
2018-08-03 17:22 ` [PATCH v5 12/15] x86: add iommu_op to enable modification of IOMMU mappings Paul Durrant
2018-08-07  4:08   ` Tian, Kevin
2018-08-07  8:32     ` Paul Durrant
2018-08-07  8:37       ` Tian, Kevin
2018-08-07  8:44         ` Paul Durrant
2018-08-07  9:01           ` Tian, Kevin
2018-08-07  9:12             ` Paul Durrant
2018-08-07  9:19               ` Tian, Kevin
2018-08-07  9:22                 ` Paul Durrant
2018-08-03 17:22 ` [PATCH v5 13/15] memory: add get_paged_gfn() as a wrapper Paul Durrant
2018-08-03 17:22 ` [PATCH v5 14/15] x86: add iommu_ops to modify and flush IOMMU mappings Paul Durrant
2018-08-03 17:22 ` [PATCH v5 15/15] x86: extend the map and unmap iommu_ops to support grant references Paul Durrant

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