Re: [XEN PATCH] x86/hvm: make stdvga support optional

["Roger Pau Monné" <roger.pau@citrix.com>]

On Thu, Sep 12, 2024 at 11:57:09AM +0300, Sergiy Kibrik wrote:
> Introduce config option X86_STDVGA so that stdvga driver can be disabled on
> systems that don't need it.
> 
> Signed-off-by: Sergiy Kibrik <Sergiy_Kibrik@epam.com>
> ---
>  xen/arch/x86/Kconfig              | 10 ++++++++++
>  xen/arch/x86/hvm/Makefile         |  2 +-
>  xen/arch/x86/include/asm/hvm/io.h |  5 +++++
>  3 files changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
> index 62f0b5e0f4..2ba25e6906 100644
> --- a/xen/arch/x86/Kconfig
> +++ b/xen/arch/x86/Kconfig
> @@ -385,6 +385,16 @@ config ALTP2M
>  
>  	  If unsure, stay with defaults.
>  
> +config X86_STDVGA
> +	bool "Standard VGA card emulation support" if EXPERT
> +	default y
> +	depends on HVM
> +	help
> +	  Build stdvga driver that emulates standard VGA card with VESA BIOS
> +          Extensions for HVM guests.
> +
> +	  If unsure, say Y.
> +
>  endmenu
>  
>  source "common/Kconfig"
> diff --git a/xen/arch/x86/hvm/Makefile b/xen/arch/x86/hvm/Makefile
> index 4c1fa5c6c2..4d1f8e00eb 100644
> --- a/xen/arch/x86/hvm/Makefile
> +++ b/xen/arch/x86/hvm/Makefile
> @@ -22,7 +22,7 @@ obj-y += pmtimer.o
>  obj-y += quirks.o
>  obj-y += rtc.o
>  obj-y += save.o
> -obj-y += stdvga.o
> +obj-$(CONFIG_X86_STDVGA) += stdvga.o
>  obj-y += vioapic.o
>  obj-y += vlapic.o
>  obj-y += vm_event.o
> diff --git a/xen/arch/x86/include/asm/hvm/io.h b/xen/arch/x86/include/asm/hvm/io.h
> index 24d1b6134f..9b8d4f6b7a 100644
> --- a/xen/arch/x86/include/asm/hvm/io.h
> +++ b/xen/arch/x86/include/asm/hvm/io.h
> @@ -128,8 +128,13 @@ struct hvm_hw_stdvga {
>      spinlock_t lock;
>  };
>  
> +#ifdef CONFIG_X86_STDVGA
>  void stdvga_init(struct domain *d);
>  void stdvga_deinit(struct domain *d);
> +#else
> +static inline void stdvga_init(struct domain *d) {}
> +static inline void stdvga_deinit(struct domain *d) {}
> +#endif

Shouldn't Xen report an error if a user attempts to create a domain
with X86_EMU_VGA set in emulation_flags, but stdvga has been built
time disabled?

Thanks, Roger.