On 02/08/2014 02:45 PM, Linus Torvalds wrote: > On Sat, Feb 8, 2014 at 11:12 AM, Richard Yao <r...@gentoo.org> wrote: > And what's the backtrace that gets mentioned - but not quoted - for > the horrible 9p crap? So that we can see who the guilty party is that > thinks that it's somehow ok to pass module addresses off to other > kernel users..
My apologies for that. Here is the backtrace: [<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 [<ffffffff810cc420>] SyS_finit_module+0x70/0xd0 [<ffffffff814a08fd>] system_call_fastpath+0x1a/0x1f [<ffffffffffffffff>] 0xffffffffffffffff The addresses are being passed to permit zero-copy between the guest and the host. You can see this in the original thread back from December, which is from before I knew how to submit patches properly: http://www.spinics.net/lists/linux-virtualization/msg21734.html > Please let's just fix the real problem, don't add more horridness on > top of it because somebody messed up earlier. This code avoids a copy between QEMU's 9p server and a guest Linux kernel. Without it, the 9p-virtio code must allocate additional buffers into which QEMU will write the data and then copy from those buffers into the actual kernel buffers. How would you like 9p-virtio to do this?
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