From: Ashok Raj <ashok.raj@intel.com>
To: Andi Kleen <ak@suse.de>
Cc: Ashok Raj <ashok.raj@intel.com>,
linux-kernel@vger.kernel.org, akpm@osdl.org, gregkh@suse.de,
muli@il.ibm.com, asit.k.mallick@intel.com,
suresh.b.siddha@intel.com, anil.s.keshavamurthy@intel.com,
arjan@linux.intel.com, shaohua.li@intel.com
Subject: Re: [Intel IOMMU][patch 4/8] Supporting Zero Length Reads in Intel IOMMU.
Date: Tue, 24 Apr 2007 13:42:08 -0700 [thread overview]
Message-ID: <20070424204208.GD27911@linux-os.sc.intel.com> (raw)
In-Reply-To: <200704242128.12057.ak@suse.de>
On Tue, Apr 24, 2007 at 09:28:11PM +0200, Andi Kleen wrote:
> On Tuesday 24 April 2007 08:03:03 Ashok Raj wrote:
> > PCI specs permit zero length reads (ZLR) even if the mapping for that region
> > is write only. Support for this feature is indicated by the presence of a bit
> > in the DMAR capability. If a particular DMAR does not support this capability
> > we map write-only regions as read-write.
> >
> > This option can also provides a workaround for some drivers that request
> > a write-only mapping when they really should request a read-write.
> > (We ran into one such case in eepro100.c in handling rx_ring_dma)
>
> Better just fix the drivers instead of adding such hacks
Some of the early DMAR's dont handle zero-length-reads as required. hardware
that supports it correctly will advertise via its capabilities.
We could remove the cmdline option since it should not be really required.
next prev parent reply other threads:[~2007-04-24 20:44 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-24 6:02 [Intel IOMMU][patch 0/8] Intel IOMMU Support Ashok Raj
2007-04-24 6:03 ` [Intel IOMMU][patch 1/8] ACPI support for Intel Virtualization Technology for Directed I/O Ashok Raj
2007-04-24 18:50 ` Andi Kleen
2007-04-24 20:17 ` Ashok Raj
2007-04-24 6:03 ` [Intel IOMMU][patch 2/8] Some generic search functions required to lookup device relationships Ashok Raj
2007-04-24 6:03 ` [Intel IOMMU][patch 3/8] Generic hardware support for Intel IOMMU Ashok Raj
2007-04-24 19:27 ` Andi Kleen
2007-04-24 20:59 ` Ashok Raj
2007-04-25 1:17 ` Shaohua Li
2007-04-25 6:53 ` Andi Kleen
2007-04-24 6:03 ` [Intel IOMMU][patch 4/8] Supporting Zero Length Reads in " Ashok Raj
2007-04-24 19:28 ` Andi Kleen
2007-04-24 20:42 ` Ashok Raj [this message]
2007-04-24 21:00 ` David Miller
2007-04-24 6:03 ` [Intel IOMMU][patch 5/8] Graphics driver workarounds to provide unity map Ashok Raj
2007-04-24 6:03 ` [Intel IOMMU][patch 6/8] Doc updates for Intel Virtualization Technology for Directed I/O Ashok Raj
2007-04-24 6:03 ` [Intel IOMMU][patch 7/8] Support for legacy ISA devices Ashok Raj
2007-04-24 19:31 ` Andi Kleen
2007-04-24 20:33 ` Arjan van de Ven
2007-04-24 20:39 ` Ashok Raj
2007-04-24 6:03 ` [Intel IOMMU][patch 8/8] Preserve some Virtual Address when devices cannot address entire range Ashok Raj
2007-04-24 19:33 ` Andi Kleen
2007-04-24 20:33 ` Ashok Raj
2007-04-24 21:12 ` Andi Kleen
2007-04-24 21:23 ` David Miller
2007-04-24 21:32 ` Roland Dreier
2007-04-24 21:47 ` David Miller
2007-04-24 21:38 ` Ashok Raj
2007-04-24 21:50 ` David Miller
2007-04-24 22:03 ` Andi Kleen
2007-04-24 22:26 ` Ashok Raj
2007-04-25 1:12 ` H. Peter Anvin
2007-04-25 6:55 ` Andi Kleen
2007-04-24 23:22 ` Alan Cox
-- strict thread matches above, loose matches on Subject: below --
2007-04-23 16:38 [Intel IOMMU][patch 0/8] Intel IOMMU Support Ashok Raj
2007-04-23 16:38 ` [Intel IOMMU][patch 4/8] Supporting Zero Length Reads in Intel IOMMU Ashok Raj
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