[PATCH] tools: specifically enable VirtFS in Linux QEMU builds

[PATCH] tools: specifically enable VirtFS in Linux QEMU builds

[Paul Durrant]

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.durrant@citrix.com>
---
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: George Dunlap <George.Dunlap@eu.citrix.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Julien Grall <julien.grall@arm.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Tim Deegan <tim@xen.org>
Cc: Wei Liu <wei.liu2@citrix.com>
---
 README         |  2 ++
 tools/Makefile | 11 +++++++++++
 2 files changed, 13 insertions(+)

diff --git a/README b/README
index 4b95b21c7b..1a4e4b2c1b 100644
--- a/README
+++ b/README
@@ -56,6 +56,8 @@ provided by your OS distributor:
       greater.
     * Development install of GLib v2.0 (e.g. libglib2.0-dev)
     * Development install of Pixman (e.g. libpixman-1-dev)
+    * Development install of libcap (e.g. libcap-dev) [Linux only]
+    * Development install of libattr (e.g. libattr1-dev) [Linux only]
     * pkg-config
     * bridge-utils package (/sbin/brctl)
     * iproute package (/sbin/ip)
diff --git a/tools/Makefile b/tools/Makefile
index 67977ad850..e74efb8a6e 100644
--- a/tools/Makefile
+++ b/tools/Makefile
@@ -216,6 +216,11 @@ else
 QEMU_XEN_ENABLE_DEBUG :=
 endif
 
+#
+# 9pfs support is a documented feature but it depends on a QEMU with
+# VirtFS enabled. However VirtFS is a Linux-only option so only enable
+# it for Linux builds.
+#
 subdir-all-qemu-xen-dir: qemu-xen-dir-find
 	unset MAKELEVEL; \
 	if test -d $(QEMU_UPSTREAM_LOC) ; then \
@@ -232,10 +237,16 @@ subdir-all-qemu-xen-dir: qemu-xen-dir-find
 	else \
 		enable_trace_backend='' ; \
 	fi ; \
+	if [ "$(CONFIG_Linux)" = "y" ]; then \
+		enable_virtfs='--enable-virtfs' ; \
+	else \
+		enable_virtfs='' ; \
+	fi ; \
 	PKG_CONFIG_PATH=$(XEN_ROOT)/tools/pkg-config$${PKG_CONFIG_PATH:+:$${PKG_CONFIG_PATH}} \
 	$$source/configure --enable-xen --target-list=i386-softmmu \
 		$(QEMU_XEN_ENABLE_DEBUG) \
 		$$enable_trace_backend \
+		$$enable_virtfs \
 		--prefix=$(LIBEXEC) \
 		--libdir=$(LIBEXEC_LIB) \
 		--includedir=$(LIBEXEC_INC) \
-- 
2.11.0


_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

Re: [PATCH] tools: specifically enable VirtFS in Linux QEMU builds

[George Dunlap]

On 09/06/2018 01:06 PM, 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.durrant@citrix.com>
> ---
> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
> Cc: George Dunlap <George.Dunlap@eu.citrix.com>
> Cc: Ian Jackson <ian.jackson@eu.citrix.com>
> Cc: Jan Beulich <jbeulich@suse.com>
> Cc: Julien Grall <julien.grall@arm.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Cc: Stefano Stabellini <sstabellini@kernel.org>
> Cc: Tim Deegan <tim@xen.org>
> Cc: Wei Liu <wei.liu2@citrix.com>
> ---
>  README         |  2 ++
>  tools/Makefile | 11 +++++++++++
>  2 files changed, 13 insertions(+)
> 
> diff --git a/README b/README
> index 4b95b21c7b..1a4e4b2c1b 100644
> --- a/README
> +++ b/README
> @@ -56,6 +56,8 @@ provided by your OS distributor:
>        greater.
>      * Development install of GLib v2.0 (e.g. libglib2.0-dev)
>      * Development install of Pixman (e.g. libpixman-1-dev)
> +    * Development install of libcap (e.g. libcap-dev) [Linux only]
> +    * Development install of libattr (e.g. libattr1-dev) [Linux only]
>      * pkg-config
>      * bridge-utils package (/sbin/brctl)
>      * iproute package (/sbin/ip)
> diff --git a/tools/Makefile b/tools/Makefile
> index 67977ad850..e74efb8a6e 100644
> --- a/tools/Makefile
> +++ b/tools/Makefile
> @@ -216,6 +216,11 @@ else
>  QEMU_XEN_ENABLE_DEBUG :=
>  endif
>  
> +#
> +# 9pfs support is a documented feature but it depends on a QEMU with
> +# VirtFS enabled. However VirtFS is a Linux-only option so only enable
> +# it for Linux builds.
> +#
>  subdir-all-qemu-xen-dir: qemu-xen-dir-find
>  	unset MAKELEVEL; \
>  	if test -d $(QEMU_UPSTREAM_LOC) ; then \
> @@ -232,10 +237,16 @@ subdir-all-qemu-xen-dir: qemu-xen-dir-find
>  	else \
>  		enable_trace_backend='' ; \
>  	fi ; \
> +	if [ "$(CONFIG_Linux)" = "y" ]; then \
> +		enable_virtfs='--enable-virtfs' ; \
> +	else \
> +		enable_virtfs='' ; \
> +	fi ; \

9pfs is still a reasonably "niche" feature; I don't think we want to
force people to enable it if they don't expect to use it.

Is it the case that if we have libcap and libattr, that qemu will enable
9pfs automatically?  If so we should just document that.

Another option would be to have "--enable-9pfs" option in the tools
configure, which would then pass this on to qemu (and thus fail if the
requisite librares aren't present), but I'm not sure if having a load of
"--enable-*" at the top level is really what we want for this.

 -George

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

Re: [PATCH] tools: specifically enable VirtFS in Linux QEMU builds

[Paul Durrant]

> -----Original Message-----
> From: George Dunlap [mailto:george.dunlap@citrix.com]
> Sent: 06 September 2018 13:52
> To: Paul Durrant <Paul.Durrant@citrix.com>; xen-devel@lists.xenproject.org
> Cc: Andrew Cooper <Andrew.Cooper3@citrix.com>; George Dunlap
> <George.Dunlap@citrix.com>; Ian Jackson <Ian.Jackson@citrix.com>; Jan
> Beulich <jbeulich@suse.com>; Julien Grall <julien.grall@arm.com>; Konrad
> Rzeszutek Wilk <konrad.wilk@oracle.com>; Stefano Stabellini
> <sstabellini@kernel.org>; Tim (Xen.org) <tim@xen.org>; Wei Liu
> <wei.liu2@citrix.com>
> Subject: Re: [PATCH] tools: specifically enable VirtFS in Linux QEMU builds
> 
> On 09/06/2018 01:06 PM, 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.durrant@citrix.com>
> > ---
> > Cc: Andrew Cooper <andrew.cooper3@citrix.com>
> > Cc: George Dunlap <George.Dunlap@eu.citrix.com>
> > Cc: Ian Jackson <ian.jackson@eu.citrix.com>
> > Cc: Jan Beulich <jbeulich@suse.com>
> > Cc: Julien Grall <julien.grall@arm.com>
> > Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> > Cc: Stefano Stabellini <sstabellini@kernel.org>
> > Cc: Tim Deegan <tim@xen.org>
> > Cc: Wei Liu <wei.liu2@citrix.com>
> > ---
> >  README         |  2 ++
> >  tools/Makefile | 11 +++++++++++
> >  2 files changed, 13 insertions(+)
> >
> > diff --git a/README b/README
> > index 4b95b21c7b..1a4e4b2c1b 100644
> > --- a/README
> > +++ b/README
> > @@ -56,6 +56,8 @@ provided by your OS distributor:
> >        greater.
> >      * Development install of GLib v2.0 (e.g. libglib2.0-dev)
> >      * Development install of Pixman (e.g. libpixman-1-dev)
> > +    * Development install of libcap (e.g. libcap-dev) [Linux only]
> > +    * Development install of libattr (e.g. libattr1-dev) [Linux only]
> >      * pkg-config
> >      * bridge-utils package (/sbin/brctl)
> >      * iproute package (/sbin/ip)
> > diff --git a/tools/Makefile b/tools/Makefile
> > index 67977ad850..e74efb8a6e 100644
> > --- a/tools/Makefile
> > +++ b/tools/Makefile
> > @@ -216,6 +216,11 @@ else
> >  QEMU_XEN_ENABLE_DEBUG :=
> >  endif
> >
> > +#
> > +# 9pfs support is a documented feature but it depends on a QEMU with
> > +# VirtFS enabled. However VirtFS is a Linux-only option so only enable
> > +# it for Linux builds.
> > +#
> >  subdir-all-qemu-xen-dir: qemu-xen-dir-find
> >  	unset MAKELEVEL; \
> >  	if test -d $(QEMU_UPSTREAM_LOC) ; then \
> > @@ -232,10 +237,16 @@ subdir-all-qemu-xen-dir: qemu-xen-dir-find
> >  	else \
> >  		enable_trace_backend='' ; \
> >  	fi ; \
> > +	if [ "$(CONFIG_Linux)" = "y" ]; then \
> > +		enable_virtfs='--enable-virtfs' ; \
> > +	else \
> > +		enable_virtfs='' ; \
> > +	fi ; \
> 
> 9pfs is still a reasonably "niche" feature; I don't think we want to
> force people to enable it if they don't expect to use it.
> 
> Is it the case that if we have libcap and libattr, that qemu will enable
> 9pfs automatically?  If so we should just document that.

Yes, that is the case but it does seem weird that we have a documented feature which is not being built in by default, because we don't call out or check for the necessary pre-requisites.

> 
> Another option would be to have "--enable-9pfs" option in the tools
> configure, which would then pass this on to qemu (and thus fail if the
> requisite librares aren't present), but I'm not sure if having a load of
> "--enable-*" at the top level is really what we want for this.
> 

That is something I wondered about. Really I just don't want people to be scrobbling around wondering why, having built and installed Xen and QEMU put a '9p' line in their config and then kicked off their guest, it simply doesn't work.

  Paul

>  -George
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

Re: [PATCH] tools: specifically enable VirtFS in Linux QEMU builds

[Stefano Stabellini]

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.durrant@citrix.com>

Thank you, Paul! Do we need to do anything for the configure stuff
(AC_CHECK_LIB in tools/configure.ac)?

> ---
> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
> Cc: George Dunlap <George.Dunlap@eu.citrix.com>
> Cc: Ian Jackson <ian.jackson@eu.citrix.com>
> Cc: Jan Beulich <jbeulich@suse.com>
> Cc: Julien Grall <julien.grall@arm.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Cc: Stefano Stabellini <sstabellini@kernel.org>
> Cc: Tim Deegan <tim@xen.org>
> Cc: Wei Liu <wei.liu2@citrix.com>
> ---
>  README         |  2 ++
>  tools/Makefile | 11 +++++++++++
>  2 files changed, 13 insertions(+)
> 
> diff --git a/README b/README
> index 4b95b21c7b..1a4e4b2c1b 100644
> --- a/README
> +++ b/README
> @@ -56,6 +56,8 @@ provided by your OS distributor:
>        greater.
>      * Development install of GLib v2.0 (e.g. libglib2.0-dev)
>      * Development install of Pixman (e.g. libpixman-1-dev)
> +    * Development install of libcap (e.g. libcap-dev) [Linux only]
> +    * Development install of libattr (e.g. libattr1-dev) [Linux only]
>      * pkg-config
>      * bridge-utils package (/sbin/brctl)
>      * iproute package (/sbin/ip)
> diff --git a/tools/Makefile b/tools/Makefile
> index 67977ad850..e74efb8a6e 100644
> --- a/tools/Makefile
> +++ b/tools/Makefile
> @@ -216,6 +216,11 @@ else
>  QEMU_XEN_ENABLE_DEBUG :=
>  endif
>  
> +#
> +# 9pfs support is a documented feature but it depends on a QEMU with
> +# VirtFS enabled. However VirtFS is a Linux-only option so only enable
> +# it for Linux builds.
> +#
>  subdir-all-qemu-xen-dir: qemu-xen-dir-find
>  	unset MAKELEVEL; \
>  	if test -d $(QEMU_UPSTREAM_LOC) ; then \
> @@ -232,10 +237,16 @@ subdir-all-qemu-xen-dir: qemu-xen-dir-find
>  	else \
>  		enable_trace_backend='' ; \
>  	fi ; \
> +	if [ "$(CONFIG_Linux)" = "y" ]; then \
> +		enable_virtfs='--enable-virtfs' ; \
> +	else \
> +		enable_virtfs='' ; \
> +	fi ; \
>  	PKG_CONFIG_PATH=$(XEN_ROOT)/tools/pkg-config$${PKG_CONFIG_PATH:+:$${PKG_CONFIG_PATH}} \
>  	$$source/configure --enable-xen --target-list=i386-softmmu \
>  		$(QEMU_XEN_ENABLE_DEBUG) \
>  		$$enable_trace_backend \
> +		$$enable_virtfs \
>  		--prefix=$(LIBEXEC) \
>  		--libdir=$(LIBEXEC_LIB) \
>  		--includedir=$(LIBEXEC_INC) \
> -- 
> 2.11.0
> 

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

Re: [PATCH] tools: specifically enable VirtFS in Linux QEMU builds

[Paul Durrant]

> -----Original Message-----
> From: Stefano Stabellini [mailto:sstabellini@kernel.org]
> Sent: 06 September 2018 19:12
> To: Paul Durrant <Paul.Durrant@citrix.com>
> Cc: xen-devel@lists.xenproject.org; Andrew Cooper
> <Andrew.Cooper3@citrix.com>; George Dunlap
> <George.Dunlap@citrix.com>; Ian Jackson <Ian.Jackson@citrix.com>; Jan
> Beulich <jbeulich@suse.com>; Julien Grall <julien.grall@arm.com>; Konrad
> Rzeszutek Wilk <konrad.wilk@oracle.com>; Stefano Stabellini
> <sstabellini@kernel.org>; Tim (Xen.org) <tim@xen.org>; Wei Liu
> <wei.liu2@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.durrant@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.

  Cheers,

    Paul

> 
> > ---
> > Cc: Andrew Cooper <andrew.cooper3@citrix.com>
> > Cc: George Dunlap <George.Dunlap@eu.citrix.com>
> > Cc: Ian Jackson <ian.jackson@eu.citrix.com>
> > Cc: Jan Beulich <jbeulich@suse.com>
> > Cc: Julien Grall <julien.grall@arm.com>
> > Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> > Cc: Stefano Stabellini <sstabellini@kernel.org>
> > Cc: Tim Deegan <tim@xen.org>
> > Cc: Wei Liu <wei.liu2@citrix.com>
> > ---
> >  README         |  2 ++
> >  tools/Makefile | 11 +++++++++++
> >  2 files changed, 13 insertions(+)
> >
> > diff --git a/README b/README
> > index 4b95b21c7b..1a4e4b2c1b 100644
> > --- a/README
> > +++ b/README
> > @@ -56,6 +56,8 @@ provided by your OS distributor:
> >        greater.
> >      * Development install of GLib v2.0 (e.g. libglib2.0-dev)
> >      * Development install of Pixman (e.g. libpixman-1-dev)
> > +    * Development install of libcap (e.g. libcap-dev) [Linux only]
> > +    * Development install of libattr (e.g. libattr1-dev) [Linux only]
> >      * pkg-config
> >      * bridge-utils package (/sbin/brctl)
> >      * iproute package (/sbin/ip)
> > diff --git a/tools/Makefile b/tools/Makefile
> > index 67977ad850..e74efb8a6e 100644
> > --- a/tools/Makefile
> > +++ b/tools/Makefile
> > @@ -216,6 +216,11 @@ else
> >  QEMU_XEN_ENABLE_DEBUG :=
> >  endif
> >
> > +#
> > +# 9pfs support is a documented feature but it depends on a QEMU with
> > +# VirtFS enabled. However VirtFS is a Linux-only option so only enable
> > +# it for Linux builds.
> > +#
> >  subdir-all-qemu-xen-dir: qemu-xen-dir-find
> >  	unset MAKELEVEL; \
> >  	if test -d $(QEMU_UPSTREAM_LOC) ; then \
> > @@ -232,10 +237,16 @@ subdir-all-qemu-xen-dir: qemu-xen-dir-find
> >  	else \
> >  		enable_trace_backend='' ; \
> >  	fi ; \
> > +	if [ "$(CONFIG_Linux)" = "y" ]; then \
> > +		enable_virtfs='--enable-virtfs' ; \
> > +	else \
> > +		enable_virtfs='' ; \
> > +	fi ; \
> >  	PKG_CONFIG_PATH=$(XEN_ROOT)/tools/pkg-
> config$${PKG_CONFIG_PATH:+:$${PKG_CONFIG_PATH}} \
> >  	$$source/configure --enable-xen --target-list=i386-softmmu \
> >  		$(QEMU_XEN_ENABLE_DEBUG) \
> >  		$$enable_trace_backend \
> > +		$$enable_virtfs \
> >  		--prefix=$(LIBEXEC) \
> >  		--libdir=$(LIBEXEC_LIB) \
> >  		--includedir=$(LIBEXEC_INC) \
> > --
> > 2.11.0
> >

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

Re: [PATCH] tools: specifically enable VirtFS in Linux QEMU builds

[Roger Pau Monné]

On Fri, Sep 07, 2018 at 08:35:11AM +0000, Paul Durrant wrote:
> > -----Original Message-----
> > From: Stefano Stabellini [mailto:sstabellini@kernel.org]
> > Sent: 06 September 2018 19:12
> > To: Paul Durrant <Paul.Durrant@citrix.com>
> > Cc: xen-devel@lists.xenproject.org; Andrew Cooper
> > <Andrew.Cooper3@citrix.com>; George Dunlap
> > <George.Dunlap@citrix.com>; Ian Jackson <Ian.Jackson@citrix.com>; Jan
> > Beulich <jbeulich@suse.com>; Julien Grall <julien.grall@arm.com>; Konrad
> > Rzeszutek Wilk <konrad.wilk@oracle.com>; Stefano Stabellini
> > <sstabellini@kernel.org>; Tim (Xen.org) <tim@xen.org>; Wei Liu
> > <wei.liu2@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.durrant@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.

Roger.

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

Re: [PATCH] tools: specifically enable VirtFS in Linux QEMU builds

[George Dunlap]

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:sstabellini@kernel.org]
>>> Sent: 06 September 2018 19:12
>>> To: Paul Durrant <Paul.Durrant@citrix.com>
>>> Cc: xen-devel@lists.xenproject.org; Andrew Cooper
>>> <Andrew.Cooper3@citrix.com>; George Dunlap
>>> <George.Dunlap@citrix.com>; Ian Jackson <Ian.Jackson@citrix.com>; Jan
>>> Beulich <jbeulich@suse.com>; Julien Grall <julien.grall@arm.com>; Konrad
>>> Rzeszutek Wilk <konrad.wilk@oracle.com>; Stefano Stabellini
>>> <sstabellini@kernel.org>; Tim (Xen.org) <tim@xen.org>; Wei Liu
>>> <wei.liu2@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.durrant@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

Re: [PATCH] tools: specifically enable VirtFS in Linux QEMU builds

[Paul Durrant]

> -----Original Message-----
> From: George Dunlap [mailto:george.dunlap@citrix.com]
> Sent: 07 September 2018 16:26
> To: Roger Pau Monne <roger.pau@citrix.com>; Paul Durrant
> <Paul.Durrant@citrix.com>
> Cc: 'Stefano Stabellini' <sstabellini@kernel.org>; Wei Liu
> <wei.liu2@citrix.com>; Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>;
> Andrew Cooper <Andrew.Cooper3@citrix.com>; Tim (Xen.org)
> <tim@xen.org>; Julien Grall <julien.grall@arm.com>; Jan Beulich
> <jbeulich@suse.com>; Ian Jackson <Ian.Jackson@citrix.com>; xen-
> devel@lists.xenproject.org
> Subject: Re: [Xen-devel] [PATCH] tools: specifically enable VirtFS in Linux
> QEMU builds
> 
> 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:sstabellini@kernel.org]
> >>> Sent: 06 September 2018 19:12
> >>> To: Paul Durrant <Paul.Durrant@citrix.com>
> >>> Cc: xen-devel@lists.xenproject.org; Andrew Cooper
> >>> <Andrew.Cooper3@citrix.com>; George Dunlap
> >>> <George.Dunlap@citrix.com>; Ian Jackson <Ian.Jackson@citrix.com>;
> Jan
> >>> Beulich <jbeulich@suse.com>; Julien Grall <julien.grall@arm.com>;
> Konrad
> >>> Rzeszutek Wilk <konrad.wilk@oracle.com>; Stefano Stabellini
> >>> <sstabellini@kernel.org>; Tim (Xen.org) <tim@xen.org>; Wei Liu
> >>> <wei.liu2@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.durrant@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.

I'd be happy with that if others are.

  Paul

> 
>  -George
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

Re: [PATCH] tools: specifically enable VirtFS in Linux QEMU builds

[Ian Jackson]

Paul Durrant writes ("RE: [Xen-devel] [PATCH] tools: specifically enable VirtFS in Linux QEMU builds"):
> George Dunlap [mailto:george.dunlap@citrix.com]
> > 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.
> 
> I'd be happy with that if others are.

SGTM.  I guess there would be osstest patch(es) to add the
dependencies and pass the new option.

Ian.

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

Re: [PATCH] tools: specifically enable VirtFS in Linux QEMU builds

[Paul Durrant]

> -----Original Message-----
> From: Ian Jackson [mailto:ian.jackson@citrix.com]
> Sent: 07 September 2018 17:19
> To: Paul Durrant <Paul.Durrant@citrix.com>
> Cc: George Dunlap <George.Dunlap@citrix.com>; Roger Pau Monne
> <roger.pau@citrix.com>; 'Stefano Stabellini' <sstabellini@kernel.org>; Wei
> Liu <wei.liu2@citrix.com>; Konrad Rzeszutek Wilk
> <konrad.wilk@oracle.com>; Andrew Cooper
> <Andrew.Cooper3@citrix.com>; Tim (Xen.org) <tim@xen.org>; Julien Grall
> <julien.grall@arm.com>; Jan Beulich <jbeulich@suse.com>; xen-
> devel@lists.xenproject.org
> Subject: RE: [Xen-devel] [PATCH] tools: specifically enable VirtFS in Linux
> QEMU builds
> 
> Paul Durrant writes ("RE: [Xen-devel] [PATCH] tools: specifically enable VirtFS
> in Linux QEMU builds"):
> > George Dunlap [mailto:george.dunlap@citrix.com]
> > > 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.
> >
> > I'd be happy with that if others are.
> 
> SGTM.  I guess there would be osstest patch(es) to add the
> dependencies and pass the new option.

Yes, they would need to follow.

  Paul

> 
> Ian.

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

Re: [PATCH] tools: specifically enable VirtFS in Linux QEMU builds

[Stefano Stabellini]

[-- Attachment #1: Type: TEXT/PLAIN, Size: 4174 bytes --]

On Fri, 7 Sep 2018, Paul Durrant wrote:
> > -----Original Message-----
> > From: George Dunlap [mailto:george.dunlap@citrix.com]
> > Sent: 07 September 2018 16:26
> > To: Roger Pau Monne <roger.pau@citrix.com>; Paul Durrant
> > <Paul.Durrant@citrix.com>
> > Cc: 'Stefano Stabellini' <sstabellini@kernel.org>; Wei Liu
> > <wei.liu2@citrix.com>; Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>;
> > Andrew Cooper <Andrew.Cooper3@citrix.com>; Tim (Xen.org)
> > <tim@xen.org>; Julien Grall <julien.grall@arm.com>; Jan Beulich
> > <jbeulich@suse.com>; Ian Jackson <Ian.Jackson@citrix.com>; xen-
> > devel@lists.xenproject.org
> > Subject: Re: [Xen-devel] [PATCH] tools: specifically enable VirtFS in Linux
> > QEMU builds
> > 
> > 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:sstabellini@kernel.org]
> > >>> Sent: 06 September 2018 19:12
> > >>> To: Paul Durrant <Paul.Durrant@citrix.com>
> > >>> Cc: xen-devel@lists.xenproject.org; Andrew Cooper
> > >>> <Andrew.Cooper3@citrix.com>; George Dunlap
> > >>> <George.Dunlap@citrix.com>; Ian Jackson <Ian.Jackson@citrix.com>;
> > Jan
> > >>> Beulich <jbeulich@suse.com>; Julien Grall <julien.grall@arm.com>;
> > Konrad
> > >>> Rzeszutek Wilk <konrad.wilk@oracle.com>; Stefano Stabellini
> > >>> <sstabellini@kernel.org>; Tim (Xen.org) <tim@xen.org>; Wei Liu
> > >>> <wei.liu2@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.durrant@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.
> 
> I'd be happy with that if others are.

If QEMU changes the virtfs default to "enable", then this option will
become ineffective maybe without us even noticing. However, I guess we
prefer to deal with duplicate enable/disable options in QEMU and Xen,
rather than duplicate dependency checks which might be harder to keep
up-to-date in the long run?

[-- Attachment #2: Type: text/plain, Size: 157 bytes --]

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

Re: [PATCH] tools: specifically enable VirtFS in Linux QEMU builds

[Stefano Stabellini]

On Fri, 7 Sep 2018, Paul Durrant wrote:
> > -----Original Message-----
> > From: Stefano Stabellini [mailto:sstabellini@kernel.org]
> > Sent: 06 September 2018 19:12
> > To: Paul Durrant <Paul.Durrant@citrix.com>
> > Cc: xen-devel@lists.xenproject.org; Andrew Cooper
> > <Andrew.Cooper3@citrix.com>; George Dunlap
> > <George.Dunlap@citrix.com>; Ian Jackson <Ian.Jackson@citrix.com>; Jan
> > Beulich <jbeulich@suse.com>; Julien Grall <julien.grall@arm.com>; Konrad
> > Rzeszutek Wilk <konrad.wilk@oracle.com>; Stefano Stabellini
> > <sstabellini@kernel.org>; Tim (Xen.org) <tim@xen.org>; Wei Liu
> > <wei.liu2@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.durrant@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?

Interesting. I don't recall ever testing this is a scenario, so I am not
surprised it is broken. I don't know why the module doesn't get loaded
automatically. FYI another thing missing is suspend/resume support in
the driver.

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

Re: [PATCH] tools: specifically enable VirtFS in Linux QEMU builds

[Paul Durrant]

> -----Original Message-----
> From: Stefano Stabellini [mailto:sstabellini@kernel.org]
> Sent: 07 September 2018 17:58
> To: Paul Durrant <Paul.Durrant@citrix.com>
> Cc: 'Stefano Stabellini' <sstabellini@kernel.org>; xen-
> devel@lists.xenproject.org; Andrew Cooper <Andrew.Cooper3@citrix.com>;
> George Dunlap <George.Dunlap@citrix.com>; Ian Jackson
> <Ian.Jackson@citrix.com>; Jan Beulich <jbeulich@suse.com>; Julien Grall
> <julien.grall@arm.com>; Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>;
> Tim (Xen.org) <tim@xen.org>; Wei Liu <wei.liu2@citrix.com>
> Subject: RE: [PATCH] tools: specifically enable VirtFS in Linux QEMU builds
> 
> On Fri, 7 Sep 2018, Paul Durrant wrote:
> > > -----Original Message-----
> > > From: Stefano Stabellini [mailto:sstabellini@kernel.org]
> > > Sent: 06 September 2018 19:12
> > > To: Paul Durrant <Paul.Durrant@citrix.com>
> > > Cc: xen-devel@lists.xenproject.org; Andrew Cooper
> > > <Andrew.Cooper3@citrix.com>; George Dunlap
> > > <George.Dunlap@citrix.com>; Ian Jackson <Ian.Jackson@citrix.com>; Jan
> > > Beulich <jbeulich@suse.com>; Julien Grall <julien.grall@arm.com>;
> Konrad
> > > Rzeszutek Wilk <konrad.wilk@oracle.com>; Stefano Stabellini
> > > <sstabellini@kernel.org>; Tim (Xen.org) <tim@xen.org>; Wei Liu
> > > <wei.liu2@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.durrant@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?
> 
> Interesting. I don't recall ever testing this is a scenario, so I am not
> surprised it is broken. I don't know why the module doesn't get loaded
> automatically. FYI another thing missing is suspend/resume support in
> the driver.

I see. I guess that probably means cycling through closing->closed and back to initwait has not been exercised in the backend. I'll bear that in mind when I get to that stage. Thanks :-)

  Paul

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel