Re: [PATCH RFC 3/3] xen: Introduce a platform sub-op to retrieve the VGA information

[Jan Beulich <jbeulich@xxxxxxxx>]

On 06.02.2022 20:28, Julien Grall wrote:
> From: Julien Grall <jgrall@xxxxxxxxxx>
> 
> When using EFI, the VGA information is fetched using the EFI
> boot services. However, Xen will have exited the boot services.
> Therefore, we need to find a different way to pass the information
> to dom0.
> 
> For PV dom0, they are part of the start_info. But this is not
> something that exists on Arm. So the best way would to be to
> use a hypercall.
> 
> For now the structure layout is based on dom0_vga_console_info
> for convenience. I am open on another proposal.
> 
> Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>

Cc-ing Roger as this may want using for PVH Dom0 also on x86; my
first attempt to propagate this information was rejected.

> --- a/xen/include/public/platform.h
> +++ b/xen/include/public/platform.h
> @@ -244,6 +244,7 @@ DEFINE_XEN_GUEST_HANDLE(xenpf_efi_runtime_call_t);
>  #define  XEN_FW_EFI_PCI_ROM        5
>  #define  XEN_FW_EFI_APPLE_PROPERTIES 6
>  #define XEN_FW_KBD_SHIFT_FLAGS    5
> +#define XEN_FW_VGA_INFO           6

Perhaps s/VGA/VIDEO/, despite ...

>  struct xenpf_firmware_info {
>      /* IN variables. */
>      uint32_t type;
> @@ -311,6 +312,7 @@ struct xenpf_firmware_info {
>  
>          /* Int16, Fn02: Get keyboard shift flags. */
>          uint8_t kbd_shift_flags; /* XEN_FW_KBD_SHIFT_FLAGS */
> +        struct dom0_vga_console_info vga;

... the structure name including "vga" (but if the #define is adjusted,
the field name would want to become "video" as well).

Jan