Re: [PATCH] xen/arm: fix the build error for GIC

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 22 Dec 2021, Julien Grall wrote:
> Hello,
> 
> On 22/12/2021 09:38, Dongjiu Geng wrote:
> > when enable CONFIG_NEW_VGIC in ARM64 QEMU Platform, it will build failed.
> > so fix it and make it can select GICV2.
> 
> Last time I checked QEMU, it was only able to support GICv3 virtualization.
> Has it changed since?
> 
> > 
> > Signed-off-by: Dongjiu Geng <gengdongjiu1@xxxxxxxxx>
> > ---
> > $ make dist-xen XEN_TARGET_ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- -j10
> > make -C xen install
> > make[1]: Entering directory
> > '/home/workspace/gengdongjiu/old_machine/XEN/xen/xen'
> > make -f
> > /home/workspace/gengdongjiu/old_machine/XEN/xen/xen/tools/kconfig/Makefile.kconfig
> > ARCH=arm64 SRCARCH=arm HOSTCC="gcc" HOSTCXX="g++" syncconfig
> > make[2]: Entering directory
> > '/home/workspace/gengdongjiu/old_machine/XEN/xen/xen'
> > gcc -Wp,-MD,tools/kconfig/.conf.o.d      -c -o tools/kconfig/conf.o
> > tools/kconfig/conf.c
> > gcc -Wp,-MD,tools/kconfig/.confdata.o.d      -c -o tools/kconfig/confdata.o
> > tools/kconfig/confdata.c
> > gcc -Wp,-MD,tools/kconfig/.expr.o.d      -c -o tools/kconfig/expr.o
> > tools/kconfig/expr.c
> > flex -otools/kconfig/lexer.lex.c -L tools/kconfig/lexer.l
> > bison -o tools/kconfig/parser.tab.c --defines=tools/kconfig/parser.tab.h -t
> > -l tools/kconfig/parser.y
> > gcc -Wp,-MD,tools/kconfig/.preprocess.o.d      -c -o
> > tools/kconfig/preprocess.o tools/kconfig/preprocess.c
> > gcc -Wp,-MD,tools/kconfig/.symbol.o.d      -c -o tools/kconfig/symbol.o
> > tools/kconfig/symbol.c
> > gcc -Wp,-MD,tools/kconfig/.lexer.lex.o.d     -I
> > /home/workspace/gengdongjiu/old_machine/XEN/xen/xen/tools/kconfig -c -o
> > tools/kconfig/lexer.lex.o tools/kconfig/lexer.lex.c
> > gcc -Wp,-MD,tools/kconfig/.parser.tab.o.d     -I
> > /home/workspace/gengdongjiu/old_machine/XEN/xen/xen/tools/kconfig -c -o
> > tools/kconfig/parser.tab.o tools/kconfig/parser.tab.c
> > gcc  -o tools/kconfig/conf tools/kconfig/conf.o tools/kconfig/confdata.o
> > tools/kconfig/expr.o tools/kconfig/lexer.lex.o tools/kconfig/parser.tab.o
> > tools/kconfig/preprocess.o tools/kconfig/symbol.o
> > tools/kconfig/conf  --syncconfig Kconfig
> > 
> > WARNING: unmet direct dependencies detected for GICV3
> >    Depends on [n]: ARM_64 [=y] && !NEW_VGIC [=y]
> >    Selected by [y]:
> >    - QEMU [=y] && <choice> && ARM_64 [=y]
> > 
> > WARNING: unmet direct dependencies detected for GICV3
> >    Depends on [n]: ARM_64 [=y] && !NEW_VGIC [=y]
> >    Selected by [y]:
> >    - QEMU [=y] && <choice> && ARM_64 [=y]
> > 
> > WARNING: unmet direct dependencies detected for GICV3
> >    Depends on [n]: ARM_64 [=y] && !NEW_VGIC [=y]
> >    Selected by [y]:
> >    - QEMU [=y] && <choice> && ARM_64 [=y]
> > make[2]: Leaving directory
> > '/home/workspace/gengdongjiu/old_machine/XEN/xen/xen'
> > make -f Rules.mk _install
> > make[2]: Entering directory
> > '/home/workspace/gengdongjiu/old_machine/XEN/xen/xen'
> > ---
> >   xen/arch/arm/platforms/Kconfig | 1 -
> >   1 file changed, 1 deletion(-)
> > 
> > diff --git a/xen/arch/arm/platforms/Kconfig b/xen/arch/arm/platforms/Kconfig
> > index c93a6b2756..6d3ee99456 100644
> > --- a/xen/arch/arm/platforms/Kconfig
> > +++ b/xen/arch/arm/platforms/Kconfig
> > @@ -15,7 +15,6 @@ config ALL_PLAT
> >   config QEMU
> >     bool "QEMU aarch virt machine support"
> >     depends on ARM_64
> > -   select GICV3
> 
> Assuming you can use Xen with GICv2 on QEMU, then this change is OK. But we
> are at risk to expose it again via another platform.
> 
> So I think it would be better to also to add a dependency !GICV3 for NEW_VGIC.

I agree. I gave it a try and turns out it is not possible to simply add:

depends on !GICV3

under NEW_VGIC because there is already a !NEW_VGIC under GICV3.
Apparently it creates a circular dependency. Instead, I did the
following and it looks like it is behaving the way we want.


diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
index ecfa6822e4..373c698018 100644
--- a/xen/arch/arm/Kconfig
+++ b/xen/arch/arm/Kconfig
@@ -35,7 +35,7 @@ config ACPI
 
 config GICV3
        bool "GICv3 driver"
-       depends on ARM_64 && !NEW_VGIC
+       depends on ARM_64
        default y
        ---help---
 
@@ -44,13 +44,14 @@ config GICV3
 
 config HAS_ITS
         bool "GICv3 ITS MSI controller support (UNSUPPORTED)" if UNSUPPORTED
-        depends on GICV3 && !NEW_VGIC
+        depends on GICV3
 
 config HVM
         def_bool y
 
 config NEW_VGIC
        bool "Use new VGIC implementation"
+       depends on !GICV3
        ---help---
 
        This is an alternative implementation of the ARM GIC interrupt