Messages in this thread | | | Date | Tue, 30 Sep 2008 13:03:19 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH 3/3] x86/iommu: use __GFP_ZERO instead of memset for GART |
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* FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:
> > yes - could you please make a new option for it, > > CONFIG_IOMMU_DEBUG_FORCE=y or so - and cover all iommus that support > > it? > > I'm not sure we are talking about the same thing. Surely, I and Joerg > are talking different things. > > GART driver doesn't need to use the IOMMU hardware at all times. GART > does a virtual mapping only when necessary (a device needs to handle > an address that it can't access to). But as I wrote, if you use > iommu=force, GART driver always use the IOMMU hardware.
yes - but iommu=force is not randconfig covered, hence it never gets tested by -tip testing. So my suggestion was a really simple patch: a new Kconfig entry that makes iommu=force default.
CONFIG_BOOTPARAM_IOMMU_FORCE=y would be the right name for it. (disabled by default, of course)
> Other x86 IOMMU drivers always use the IOMMU hardware. Except for > Intel VT-D, they manage free virtual I/O space in the round-robin > manner with the bitmap algorithm to avoid frequent IOTLB flush. Joerg > said he tested AMD IOMMU driver with the round-robin manner disabled > so AMD IOMMU driver uses the same virtual I/O space with lots of IOTLB > flush.
all i'm suggesting is to please expose existing debug capabilities in the .config space, so that it can be tested in automated setups.
Ingo
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