On 2015/3/23 6:11, Rafael J. Wysocki wrote:

On Sunday, March 22, 2015 09:32:48 PM Julien Grall wrote:

quoted

On 22/03/2015 21:49, Rafael J. Wysocki wrote:

quoted

On Sunday, March 22, 2015 09:05:21 PM Julien Grall wrote:

quoted

Hello,

On 21/03/2015 12:09, Naresh Bhat wrote:

quoted

      From 268dcdafa34a690e2f99c0784ca33a6d2352ecf5 Mon Sep 17 00:00:00 2001
     From: Hanjun Guo <hanjun.guo at linaro.org <mailto:hanjun.guo@linaro.org>>
     Date: Sat, 21 Mar 2015 14:43:54 +0800
     Subject: [PATCH] XEN / ACPI: Make XEN ACPI depend on X86

     When ACPI is enabled on ARM64, XEN ACPI will also compiled
     into the kernel, but XEN ACPI is x86 dependent, so introduce
     CONFIG_XEN_ACPI to make it depend on x86 before XEN ACPI is
     functional on ARM64.

     Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org
     <mailto:hanjun.guo@linaro.org>>
     ---
       drivers/xen/Kconfig  | 4 ++++
       drivers/xen/Makefile | 2 +-
       2 files changed, 5 insertions(+), 1 deletion(-)

     diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
     index b812462..a31cd29 100644
     --- a/drivers/xen/Kconfig
     +++ b/drivers/xen/Kconfig
     @@ -253,4 +253,8 @@ config XEN_EFI
           def_bool y
           depends on X86_64 && EFI

     +config XEN_ACPI
     +    def_bool y
     +    depends on X86 && ACPI
     +
       endmenu
     diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile
     index 2ccd359..f4622ab 100644
     --- a/drivers/xen/Makefile
     +++ b/drivers/xen/Makefile
     @@ -13,7 +13,7 @@ CFLAGS_efi.o                += -fshort-wchar

       dom0-$(CONFIG_PCI) += pci.o
       dom0-$(CONFIG_USB_SUPPORT) += dbgp.o
     -dom0-$(CONFIG_ACPI) += acpi.o $(xen-pad-y)
     +dom0-$(CONFIG_XEN_ACPI) += acpi.o $(xen-pad-y)
       xen-pad-$(CONFIG_X86) += xen-acpi-pad.o
       dom0-$(CONFIG_X86) += pcpu.o
       obj-$(CONFIG_XEN_DOM0)            += $(dom0-y)

[..]

quoted

AFAIK,  There is already a kernel patch exists to fix this issue.  I
think  Julien or Parth is a right person to ask.  Hence I am CCed Julien
Grall too.

The ACPI support for Xen is not ready. So I think avoiding to compile
drivers/xen/acpi.c on ARM64/ARM seems the better solution for now.

Although, rather than introducing a new CONFIG option, I would use the
same trick we use within the Makefile to avoid hotplug.c on ARM/ARM64.

ifeq ($(filter y, $(CONFIG_ARM) $(CONFIG_ARM64)), )
dom0-$(CONFIG_ACPI) += acpi.o $(xen-pad-y)
endif

Well, is avoiding an extra CONFIG_ option worth the ugliness of this?

When the support of ACPI for Xen will come, the CONFIG_ option will be 
an alias to CONFIG_XEN.

In this case the CONFIG_ option won't bring much improvement to the code 
and add an extra indirection.

The "ugliness" option has, at least, the advantage to be tiny and 
self-contained.

Oh well, not really.  You're moving a config-time check to compile time
which means that it will be done every time this Makefile is executed
and for all architectures that execute it.  Not nice.

Also I think that ia64 is missing from the list, but I may be wrong.

In commit d52eefb47d (ia64/xen: Remove Xen support for ia64), XEN is
not supported anymore on ia64 now.

Not to mention the fact that the dependency will be rather difficult to find
for tools like xconfig ...

I also think introducing a CONFIG_ option is a better idea.

Thanks
Hanjun