[Buildroot] [PATCH 0/3] package/qemu: add option to enable guest agent

[Buildroot] [PATCH 0/3] package/qemu: add option to enable guest agent

[unixmania]

From: Carlos Santos <unixmania@gmail.com>

Before doing it, fix two small erros in the configuration menu that can lead
to build failures.

Carlos Santos (3):
  package/qemu: make "custom targets" config depend on !BR2_STATIC_LIBS
  package/qemu: select FDT for custom targets too
  package/qemu: add option to enable guest agent

 package/qemu/Config.in | 18 +++++++++++++++++-
 package/qemu/qemu.mk   |  6 ++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

-- 
2.31.1

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[Buildroot] [PATCH 1/3] package/qemu: make "custom targets" config depend on !BR2_STATIC_LIBS

[unixmania]

From: Carlos Santos <unixmania@gmail.com>

Custom targets selects system and Linux user-land emulation, which in
their turn require shared libraries.

Signed-off-by: Carlos Santos <unixmania@gmail.com>
---
 package/qemu/Config.in | 1 +
 1 file changed, 1 insertion(+)

diff --git a/package/qemu/Config.in b/package/qemu/Config.in
index 15d6c7d6b5..8b8a999885 100644
--- a/package/qemu/Config.in
+++ b/package/qemu/Config.in
@@ -51,6 +51,7 @@ comment "Emulators selection"
 
 config BR2_PACKAGE_QEMU_CUSTOM_TARGETS
 	string "Enable specific targets"
+	depends on !BR2_STATIC_LIBS # dtc
 	help
 	  Enter here the list of QEMU targets you want to build. For
 	  example:
-- 
2.31.1

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[Buildroot] [PATCH 2/3] package/qemu: select FDT for custom targets too

[unixmania]

From: Carlos Santos <unixmania@gmail.com>

Custom targets selects system and Linux user-land emulation, which in
their turn require FDT. Move the BR2_PACKAGE_QEMU_FDT selection to the
BR2_PACKAGE_QEMU_HAS_EMULS hidden boolean, to cover all cases.

Signed-off-by: Carlos Santos <unixmania@gmail.com>
---
 package/qemu/Config.in | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/package/qemu/Config.in b/package/qemu/Config.in
index 8b8a999885..9e0cbd4acf 100644
--- a/package/qemu/Config.in
+++ b/package/qemu/Config.in
@@ -95,7 +95,6 @@ comment "... or you can select emulator families to enable, below:"
 config BR2_PACKAGE_QEMU_SYSTEM
 	bool "Enable all systems emulation"
 	depends on !BR2_STATIC_LIBS # dtc
-	select BR2_PACKAGE_QEMU_FDT
 	help
 	  Say 'y' to build all system emulators/virtualisers that QEMU
 	  supports.
@@ -121,6 +120,7 @@ endif # BR2_PACKAGE_QEMU_CUSTOM_TARGETS == ""
 config BR2_PACKAGE_QEMU_HAS_EMULS
 	def_bool y
 	depends on BR2_PACKAGE_QEMU_SYSTEM || BR2_PACKAGE_QEMU_LINUX_USER || BR2_PACKAGE_QEMU_CUSTOM_TARGETS != ""
+	select BR2_PACKAGE_QEMU_FDT
 
 if BR2_PACKAGE_QEMU_HAS_EMULS
 
-- 
2.31.1

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[Buildroot] [PATCH 3/3] package/qemu: add option to enable guest agent

[unixmania]

From: Carlos Santos <unixmania@gmail.com>

It requires --enable-system or --enable-tools to be built, so add a
hidden boolean, BR2_PACKAGE_QEMU_HAS_SYSTEM_OR_TOOLS, to control it.

Signed-off-by: Carlos Santos <unixmania@gmail.com>
---
 package/qemu/Config.in | 15 +++++++++++++++
 package/qemu/qemu.mk   |  6 ++++++
 2 files changed, 21 insertions(+)

diff --git a/package/qemu/Config.in b/package/qemu/Config.in
index 9e0cbd4acf..dd8b3d3491 100644
--- a/package/qemu/Config.in
+++ b/package/qemu/Config.in
@@ -122,6 +122,10 @@ config BR2_PACKAGE_QEMU_HAS_EMULS
 	depends on BR2_PACKAGE_QEMU_SYSTEM || BR2_PACKAGE_QEMU_LINUX_USER || BR2_PACKAGE_QEMU_CUSTOM_TARGETS != ""
 	select BR2_PACKAGE_QEMU_FDT
 
+config BR2_PACKAGE_QEMU_HAS_SYSTEM_OR_TOOLS
+	def_bool y
+	depends on BR2_PACKAGE_QEMU_SYSTEM || BR2_PACKAGE_QEMU_CUSTOM_TARGETS != "" || BR2_PACKAGE_QEMU_TOOLS
+
 if BR2_PACKAGE_QEMU_HAS_EMULS
 
 comment "Frontends"
@@ -158,4 +162,15 @@ config BR2_PACKAGE_QEMU_TOOLS
 	  Say 'y' here to include tools packaged with QEMU
 	  (e.g. qemu-img).
 
+config BR2_PACKAGE_QEMU_GUEST_AGENT
+	bool "Enable guest agent"
+	depends on BR2_PACKAGE_QEMU_HAS_SYSTEM_OR_TOOLS
+	help
+	  Say 'y' here to include an agent to run on guests, which
+	  communicates with the host over a virtio-serial channel
+	  named "org.qemu.guest_agent.0".
+
+comment "Guest agent needs systems emulation or tools"
+	depends on !BR2_PACKAGE_QEMU_HAS_SYSTEM_OR_TOOLS
+
 endif # BR2_PACKAGE_QEMU
diff --git a/package/qemu/qemu.mk b/package/qemu/qemu.mk
index a991d49993..d9bdfe0e84 100644
--- a/package/qemu/qemu.mk
+++ b/package/qemu/qemu.mk
@@ -90,6 +90,12 @@ else
 QEMU_OPTS += --disable-tools
 endif
 
+ifeq ($(BR2_PACKAGE_QEMU_GUEST_AGENT),y)
+QEMU_OPTS += --enable-guest-agent
+else
+QEMU_OPTS += --disable-guest-agent
+endif
+
 ifeq ($(BR2_PACKAGE_LIBFUSE3),y)
 QEMU_OPTS += --enable-fuse --enable-fuse-lseek
 QEMU_DEPENDENCIES += libfuse3
-- 
2.31.1

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Re: [Buildroot] [PATCH 2/3] package/qemu: select FDT for custom targets too

[Thomas Huth]

Am Fri,  4 Nov 2022 20:57:26 -0300
schrieb unixmania@gmail.com:

> From: Carlos Santos <unixmania@gmail.com>
> 
> Custom targets selects system and Linux user-land emulation, which in
> their turn require FDT. Move the BR2_PACKAGE_QEMU_FDT selection to the
> BR2_PACKAGE_QEMU_HAS_EMULS hidden boolean, to cover all cases.
> 
> Signed-off-by: Carlos Santos <unixmania@gmail.com>
> ---
>  package/qemu/Config.in | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/package/qemu/Config.in b/package/qemu/Config.in
> index 8b8a999885..9e0cbd4acf 100644
> --- a/package/qemu/Config.in
> +++ b/package/qemu/Config.in
> @@ -95,7 +95,6 @@ comment "... or you can select emulator families to enable, below:"
>  config BR2_PACKAGE_QEMU_SYSTEM
>  	bool "Enable all systems emulation"
>  	depends on !BR2_STATIC_LIBS # dtc
> -	select BR2_PACKAGE_QEMU_FDT
>  	help
>  	  Say 'y' to build all system emulators/virtualisers that QEMU
>  	  supports.
> @@ -121,6 +120,7 @@ endif # BR2_PACKAGE_QEMU_CUSTOM_TARGETS == ""
>  config BR2_PACKAGE_QEMU_HAS_EMULS
>  	def_bool y
>  	depends on BR2_PACKAGE_QEMU_SYSTEM || BR2_PACKAGE_QEMU_LINUX_USER || BR2_PACKAGE_QEMU_CUSTOM_TARGETS != ""
> +	select BR2_PACKAGE_QEMU_FDT

Technically, I think you don't need FDT if you are only compiling the
linux-user targets ... so maybe it would be better to add this to the
BR2_PACKAGE_QEMU_CUSTOM_TARGETS switch instead?

 Thomas
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Re: [Buildroot] [PATCH 2/3] package/qemu: select FDT for custom targets too

[Carlos Santos]

On Sat, Nov 5, 2022 at 7:44 AM Thomas Huth <huth@tuxfamily.org> wrote:
>
> Am Fri,  4 Nov 2022 20:57:26 -0300
> schrieb unixmania@gmail.com:
>
> > From: Carlos Santos <unixmania@gmail.com>
> >
> > Custom targets selects system and Linux user-land emulation, which in
> > their turn require FDT. Move the BR2_PACKAGE_QEMU_FDT selection to the
> > BR2_PACKAGE_QEMU_HAS_EMULS hidden boolean, to cover all cases.
> >
> > Signed-off-by: Carlos Santos <unixmania@gmail.com>
> > ---
> >  package/qemu/Config.in | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/package/qemu/Config.in b/package/qemu/Config.in
> > index 8b8a999885..9e0cbd4acf 100644
> > --- a/package/qemu/Config.in
> > +++ b/package/qemu/Config.in
> > @@ -95,7 +95,6 @@ comment "... or you can select emulator families to enable, below:"
> >  config BR2_PACKAGE_QEMU_SYSTEM
> >       bool "Enable all systems emulation"
> >       depends on !BR2_STATIC_LIBS # dtc
> > -     select BR2_PACKAGE_QEMU_FDT
> >       help
> >         Say 'y' to build all system emulators/virtualisers that QEMU
> >         supports.
> > @@ -121,6 +120,7 @@ endif # BR2_PACKAGE_QEMU_CUSTOM_TARGETS == ""
> >  config BR2_PACKAGE_QEMU_HAS_EMULS
> >       def_bool y
> >       depends on BR2_PACKAGE_QEMU_SYSTEM || BR2_PACKAGE_QEMU_LINUX_USER || BR2_PACKAGE_QEMU_CUSTOM_TARGETS != ""
> > +     select BR2_PACKAGE_QEMU_FDT
>
> Technically, I think you don't need FDT if you are only compiling the
> linux-user targets ... so maybe it would be better to add this to the
> BR2_PACKAGE_QEMU_CUSTOM_TARGETS switch instead?
>
>  Thomas

BR2_PACKAGE_QEMU_CUSTOM_TARGETS is a string, so adding a "select
BR2_PACKAGE_QEMU_FDT" does not have any effect.

A better solution for the case in which only linux-user targets are
selected requires a more complex approach. I will submit a separate
patch for this purpose. Meanwhile, let's put this series on hold.

-- 
Carlos Santos <unixmania@gmail.com>
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Re: [Buildroot] [PATCH 1/3] package/qemu: make "custom targets" config depend on !BR2_STATIC_LIBS

[Thomas Petazzoni via buildroot]

Hello Carlos,

On Fri,  4 Nov 2022 20:57:25 -0300
unixmania@gmail.com wrote:

> From: Carlos Santos <unixmania@gmail.com>
> 
> Custom targets selects system and Linux user-land emulation, which in
> their turn require shared libraries.
> 
> Signed-off-by: Carlos Santos <unixmania@gmail.com>

Could you clarify which configuration fails to build?

>  config BR2_PACKAGE_QEMU_CUSTOM_TARGETS
>  	string "Enable specific targets"
> +	depends on !BR2_STATIC_LIBS # dtc

What is the relationship with DTC here?

Also, when we have a !BR2_STATIC_LIBS dependency, we normally add a
Config.in comment:

comment "specific targets need a toolchain w/ shared library"
	depends on BR2_STATIC_LIBS

But really the most important thing is to get more details to
understand better the problem.

Thanks!

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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Re: [Buildroot] [PATCH 2/3] package/qemu: select FDT for custom targets too

[Thomas Petazzoni via buildroot]

On Sat, 5 Nov 2022 17:23:53 -0300
Carlos Santos <unixmania@gmail.com> wrote:

> BR2_PACKAGE_QEMU_CUSTOM_TARGETS is a string, so adding a "select
> BR2_PACKAGE_QEMU_FDT" does not have any effect.
> 
> A better solution for the case in which only linux-user targets are
> selected requires a more complex approach. I will submit a separate
> patch for this purpose. Meanwhile, let's put this series on hold.

Hm, I think I start to understand the issue, and with the current
organization of the Config.in options in package/qemu/Config.in, it's
going to be difficult to fix in a correct way.

For example, it looks like the linux-user mode emulation doesn't work
with the musl C library:

config BR2_PACKAGE_QEMU_LINUX_USER
        bool "Enable all Linux user-land emulation"
        # Incompatible "struct sigevent" definition on musl
        depends on !BR2_TOOLCHAIN_USES_MUSL

So, it means that BR2_PACKAGE_QEMU_CUSTOM_TARGETS="i386-linux-user"
will in fact fail to build with a musl toolchain...

I only sane way to address this I believe would be to remove
BR2_PACKAGE_QEMU_CUSTOM_TARGETS entirely, and instead have
BR2_PACKAGE_QEMU_SYSTEM_TARGETS and
BR2_PACKAGE_QEMU_LINUX_USER_TARGETS, which would only be accessible
when BR2_PACKAGE_QEMU_SYSTEM or BR2_PACKAGE_QEMU_LINUX_USER
respectively are enabled. When BR2_PACKAGE_QEMU_SYSTEM_TARGETS is
empty, all system emulation targets are built, otherwise only the
specified ones are built. Ditto for the user emulation targets.

Obviously as usual, the main drawback is that is breaks backward
compatibility with existing configurations...

The other approach, which you took, is to assume for the "worst", and
assume that when BR2_PACKAGE_QEMU_CUSTOM_TARGETS != "", we might build
system or user emulation targets, and therefore this option needs to
have the combination of the dependencies of the system and user
emulation options.... which would mean disabling this option with musl
toolchains, for example.

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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