Re: [PATCH v2] xen/arm: fix the build error for GIC on ARM64 QEMU Platform

[Dongjiu Geng <gengdongjiu1@xxxxxxxxx>]

Julien Grall <julien@xxxxxxx> 于2021年12月24日周五 22:21写道：
>
> Hi,
>
> I am not sure why you dropped the others. I have added them back.

sorry, it is my mistake

>
> On 24/12/2021 14:36, Dongjiu Geng wrote:
> > Julien Grall <julien@xxxxxxx> 于2021年12月24日周五 21:25写道：
> >>
> >> Hi,
> >>
> >> On 24/12/2021 13:24, 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.
> >>
> >> As I said in v1, last time I checked QEMU was only able to support
> >> virtualization with GICv3. This is why we added a depends on.
> >
> > I enabled CONFIG_NEW_VGIC, then it will use GICv2. In my check, it
> > does not report an error.
> > My QEMU emulator version is 4.0.0.  What is the QEMU version that you used?
>
> I am using a more recent QEMU. However, I have always only used GICv3
> becuase it was IIRC there first.
>
> >
> >>
> >> If you want to remove it, then I think you ought to explain in the
> >> commit message why this is fine. A pointer to the commit or a QEMU
> >> version used would be useful.
> >
> > OK，thanks. Can you check if QEMU 4.0.0 is workable with GICv2 on your side?
>
> I don't have direct access to my QEMU setup at the moment. However,
> looking at the history.
>
> So I would suggest the following commit message:
>
> "
> xen/arm: Allow QEMU platform to be built with GICv2
>
> Trying to select PLATFORM_QEMU with NEW_VGIC will result to Kconfig
> complain about unmet dependencies:
>
> 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]
>
>
> It turns out that QEMU has been supporting GICv2 virtualization since
> v3.1.0. So an easy way to solve the issue and allow more custom support
> is to remove the dependencies on GICv3.
> "

Ok, thanks very much for your suggestion.

>
> > It is workable on my side.
> >
> >
> >>
> >>>
> >>> 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/Kconfig           | 5 +++--
> >>>    xen/arch/arm/platforms/Kconfig | 1 -
> >>>    2 files changed, 3 insertions(+), 3 deletions(-)
> >>>
> >>> 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
> >>
> >> The change in arch/arm/Kconfig is not really related to this patch.
> >> Technically the part in platforms/Kconfig is sufficient. I still think
> >> the change is good to have but it should be in a separate patch.
> >
> > sure
> >
> >>
> >>> @@ -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
> >>> 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
> >>>        select HAS_PL011
> >>>        ---help---
> >>>        Enable all the required drivers for QEMU aarch64 virt emulated
>
> While writing a proposal for the commit message, I remembered that the
> goal of CONFIG_QEMU was to select all the required drivers to be able to
> boot Xen on QEMU.
>
> AFAICT, if you start from tiny64_defconfig, you would not have GICv3
> selected. So we would technically break users of QEMU with GICv3.

I think I can add CONFIG_GICV3=y in arch/arm/configs/tiny64_defconfig
to this patch, if it must to use GICV3.

>
> I am not entirely sure how to approach it. I can think of 2 options:
>
>   1) Use 'select GICv3 if !NEW_VGIC'
>   2) Add a specific platform for QEMU new vGIC
>
> I have the feeling that 1) will result to same unmet dependency issue.
> Stefano any opinions?

Stefano?

>
> Cheers,
>
> --
> Julien Grall