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Groups > linux.kernel > #1160418
| From | Jiang Liu <jiang.liu@linux.intel.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [RFC Patch V1] ioatdma: Ignore IOAT devices under hotplug-capable PCI host bridge |
| Date | 2015-06-08 13:50 +0200 |
| Message-ID | <pz3IZ-5SA-1@gated-at.bofh.it> (permalink) |
| References | <pwO1I-1l3-5@gated-at.bofh.it> <pwO1I-1l3-3@gated-at.bofh.it> <pz2MV-4vP-3@gated-at.bofh.it> |
| Organization | Intel |
On 2015/6/8 18:42, Vinod Koul wrote: > On Tue, Jun 02, 2015 at 02:37:31PM +0800, Jiang Liu wrote: >> Ccing Rafael, it's ACPI hotplug related. >> >> On 2015/6/2 14:36, Jiang Liu wrote: >>> The dmaengine core assumes that async DMA devices will only be removed >>> when they not used anymore, or it assumes dma_async_device_unregister() >>> will only be called by dma driver exit routines. But this assumption is >>> not true for the IOAT driver, which calls dma_async_device_unregister() >>> from ioat_remove(). So current IOAT driver doesn't support device >>> hot-removal because it may cause system crash to hot-remove an inuse >>> IOAT device. >>> >>> To support CPU socket hot-removal, all PCI devices, including IOAT >>> devices embedded in the socket, will be hot-removed. The idea solution >>> is to enhance the dmaengine core and IOAT driver to support hot-removal, >>> but that's too hard. >>> >>> This patch implements a hack to disable IOAT devices under hotplug-capable >>> CPU socket so it won't break socket hot-removal. >>> > So below looks okay though I wonder how hard would it be to fix hot unplug ? Hi Vinod, Thanks for review. About three years ago I worked out a patch set to enhance the dmaengine core and ioat device driver to support hot-removal. But it has been rejected due to concerns about performance penalty caused by usage tracking. To support hot-removal, we need to track dma channel usage and a way to reclaim dma channels when hot-removing. This may cause sensible performance penalty. Recently I have tried again but still haven't find a way to support hot-removal. So eventually I suggest to disable IOAT device on hot-plug capable systems. Thanks! Gerry -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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Re: [RFC Patch V1] ioatdma: Ignore IOAT devices under hotplug-capable PCI host bridge Vinod Koul <vinod.koul@intel.com> - 2015-06-08 12:50 +0200 Re: [RFC Patch V1] ioatdma: Ignore IOAT devices under hotplug-capable PCI host bridge Jiang Liu <jiang.liu@linux.intel.com> - 2015-06-08 13:50 +0200
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