On Jan 30, 2014, at 7:44 PM, David Miller <[email protected]> wrote:
> From: David Miller <[email protected]> > Date: Thu, 30 Jan 2014 16:29:26 -0800 (PST) > >> From: Richard Yao <[email protected]> >> Date: Thu, 30 Jan 2014 13:02:48 -0500 >> >>> The 9p-virtio transport does zero copy on things larger than 1024 bytes >>> in size. It accomplishes this by returning the physical addresses of >>> pages to the virtio-pci device. At present, the translation is usually a >>> bit shift. >>> >>> However, that approach produces an invalid page address when we >>> read/write to vmalloc buffers, such as those used for Linux kernle >>> modules. This causes QEMU to die printing: >>> >>> qemu-system-x86_64: virtio: trying to map MMIO memory >>> >>> This patch enables 9p-virtio to correctly handle this case. This not >>> only enables us to load Linux kernel modules off virtfs, but also >>> enables ZFS file-based vdevs on virtfs to be used without killing QEMU. >>> >>> Also, special thanks to both Avi Kivity and Alexander Graf for their >>> interpretation of QEMU backtraces. Without their guidence, tracking down >>> this bug would have taken much longer. >>> >>> Signed-off-by: Richard Yao <[email protected]> >>> Acked-by: Alexander Graf <[email protected]> >>> Reviewed-by: Will Deacon <[email protected]> >> >> Applied, thanks. > > Actually I had to revert, is_vmalloc_or_malloc_addr() is not exported to > modules, so this change breaks the build. Thanks for catching that. I had originally used is_vmalloc_addr() instead of is_vmalloc_or_malloc_addr(), but changed it after realizing this did not correct the problem on all architectures. The is_vmalloc_addr() lives in headers. I will send out a patch to get that symbol exported and resubmit this after it is merged.-- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
