Richard Yao b9776f5963 9p/trans_virtio.c: Fix broken zero-copy on vmalloc() buffers ... [ Upstream commit b6f52ae2f0d32387bde2b89883e3b64d88b9bfe8 ] 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. That approach produces an invalid page address when we read/write to vmalloc buffers, such as those used for Linux kernel modules. Any attempt to load a Linux kernel module from 9p-virtio produces the following stack. [<ffffffff814878ce>] p9_virtio_zc_request+0x45e/0x510 [<ffffffff814814ed>] p9_client_zc_rpc.constprop.16+0xfd/0x4f0 [<ffffffff814839dd>] p9_client_read+0x15d/0x240 [<ffffffff811c8440>] v9fs_fid_readn+0x50/0xa0 [<ffffffff811c84a0>] v9fs_file_readn+0x10/0x20 [<ffffffff811c84e7>] v9fs_file_read+0x37/0x70 [<ffffffff8114e3fb>] vfs_read+0x9b/0x160 [<ffffffff81153571>] kernel_read+0x41/0x60 [<ffffffff810c83ab>] copy_module_from_fd.isra.34+0xfb/0x180 Subsequently, QEMU will 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. 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. Also, special thanks to Linus Torvalds for his insightful explanation of why this should use is_vmalloc_addr() instead of is_vmalloc_or_module_addr(): https://lkml.org/lkml/2014/2/8/272 Signed-off-by: Richard Yao <ryao@gentoo.org> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2014-03-06 21:30:03 -08:00
..
client.c	net/9p: Handle error in zero copy request correctly for 9p2000.u	2013-05-28 11:47:57 -05:00
error.c	hlist: drop the node parameter from iterators	2013-02-27 19:10:24 -08:00
Kconfig	net/9p: remove depends on CONFIG_EXPERIMENTAL	2013-01-11 11:39:33 -08:00
Makefile	[net/9p] Preparation and helper functions for zero copy	2011-03-15 09:57:34 -05:00
mod.c	9p: Reduce object size with CONFIG_NET_9P_DEBUG	2012-01-05 10:51:44 -06:00
protocol.c	9p: Modify the stat structures to use kuid_t and kgid_t	2013-02-12 03:19:31 -08:00
protocol.h	net/9p: Convert net/9p protocol dumps to tracepoints	2011-10-24 11:13:12 -05:00
trans_common.c	9p: fix off by one causing access violations and memory corruption	2013-07-28 16:29:58 -07:00
trans_common.h	fs/9p: Update zero-copy implementation in 9p	2011-10-24 11:13:11 -05:00
trans_fd.c	The following changes since commit 4cbe5a555f:	2012-10-12 09:59:23 +09:00
trans_rdma.c	9p: Reduce object size with CONFIG_NET_9P_DEBUG	2012-01-05 10:51:44 -06:00
trans_virtio.c	9p/trans_virtio.c: Fix broken zero-copy on vmalloc() buffers	2014-03-06 21:30:03 -08:00
util.c	net/9p: convert to idr_alloc()	2013-02-27 19:10:20 -08:00