On 09/07/2018 03:57 PM, Roger Pau Monné wrote: > On Fri, Sep 07, 2018 at 08:35:11AM +0000, Paul Durrant wrote: >>> -----Original Message----- >>> From: Stefano Stabellini [mailto:sstabell...@kernel.org] >>> Sent: 06 September 2018 19:12 >>> To: Paul Durrant <paul.durr...@citrix.com> >>> Cc: xen-devel@lists.xenproject.org; Andrew Cooper >>> <andrew.coop...@citrix.com>; George Dunlap >>> <george.dun...@citrix.com>; Ian Jackson <ian.jack...@citrix.com>; Jan >>> Beulich <jbeul...@suse.com>; Julien Grall <julien.gr...@arm.com>; Konrad >>> Rzeszutek Wilk <konrad.w...@oracle.com>; Stefano Stabellini >>> <sstabell...@kernel.org>; Tim (Xen.org) <t...@xen.org>; Wei Liu >>> <wei.l...@citrix.com> >>> Subject: Re: [PATCH] tools: specifically enable VirtFS in Linux QEMU builds >>> >>> On Thu, 6 Sep 2018, Paul Durrant wrote: >>>> 9pfs support has been a documented feature since Xen 4.9, but QEMU will >>>> not be built with backend support unless libcap and libattr dev packages >>>> are installed. >>>> >>>> This patch modifies the README to call out those packages as pre- >>> requisites >>>> for Linux builds and specifically enables VirtFS in the configure line >>>> for QEMU so that an error message is displayed if they are missing. >>>> >>>> Signed-off-by: Paul Durrant <paul.durr...@citrix.com> >>> >>> Thank you, Paul! >> >> NP. I'm at the point of seriously considering a Windows frontend, which is >> why I've been playing. >> >> BTW, as a heads-up... Before I realised QEMU was not building the backend, I >> tried a modprobe of the Xen 9pfs transport module in a Linux guest and >> immediately hit a kernel BUG (NULL ptr IIRC) which was apparently down to >> the frontend expecting the backend to be present when its probe routine is >> run, rather than deferring things until the backend goes into InitWait >> (which is what a frontend generally should do). Also, it's non-obvious why I >> have to explicitly modprobe anyway... Shouldn't the module get demand-loaded >> when I run mount -t 9pfs blah? >> >>> Do we need to do anything for the configure stuff >>> (AC_CHECK_LIB in tools/configure.ac)? >> >> That's certainly a reasonable belt'n'braces approach so that folks don't >> have to wait until their tools build fails to find out what they need. I'll >> have a look at that. > > IMO I don't think we should be duplicating the checks that QEMU > configure already does in our configure script. The best option would > be to run whatever external configure scripts there are together with > our own configure script, but this is quite complicated because the > qemu-dir might have to be fetched at the point where configure runs.
Not the least because the dependencies may change. I think adding an "--enable-9pfs" option which will pass on the requisite "--enable" to qemu (such that qemu build will fail if the prereqs are not present) makes the most sense. -George _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
