Messages in this thread | | | Subject | Remapping pages mapped to userspace (was: [PATCH 10 of 20] ipath - support for userspace apps using core driver) | From | Roland Dreier <> | Date | Thu, 16 Mar 2006 15:51:51 -0800 |
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[Err, sorry about the empty mail...]
Anyway, I'd like to hijack this thread slightly, since we are close to a subject that I've been thinking about lately, and I'd like to take advantage of the expert's attention...
My mthca driver (drivers/infiniband/hw/mthca) supports mapping some MMIO registers into userspace via io_remap_pfn_range() in a .mmap method. I think I have that pretty well under control.
However, on a hot unplug event, when the underlying PCI device is going away, I would like to replace that mapping with a mapping (with a mapping to the zero page?), so that userspace accesses after the device is gone don't explode. What's the "right" way to do that?
Presumably it would be something like zeromap_page_range(), but that's not exported to modules. Exporting that would be one option, but in a way that's overkill for me: I only have a single page to deal with, so I could also do something like
vm_insert_page(vma, addr, ZERO_PAGE(addr));
But do I have to do anything to kill the old mapping coming from remap_pfn_range()? What's the exported API to do that?
I can keep a list of vmas that have registers mapped to userspace and iterate through it on hot unplug. The only question is what to do with those vmas.
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