Re: [PATCH v2 2/5] xen/vioapic: add support for the extended destination ID field

[Jan Beulich <jbeulich@xxxxxxxx>]

On 16.02.2022 11:30, Roger Pau Monne wrote:
> Such field uses bits 55:48, but for the purposes the register will be
> used use bits 55:49 instead. Bit 48 is used to signal an RTE entry is
> in remappable format which is not supported by the vIO-APIC.

Nit: The first sentence looks to have some stray words.

> --- a/tools/include/libxl.h
> +++ b/tools/include/libxl.h
> @@ -527,6 +527,14 @@
>   */
>  #define LIBXL_HAVE_MAX_GRANT_VERSION 1
>  
> +/*
> + * LIBXL_HAVE_X86_EXT_DEST_ID indicates the toolstack can signal to the
> + * hypervisor whether the domain wants to use the extended destination ID 
> mode
> + * for interrupt messages. This is done by setting the 
> libxl_domain_build_info
> + * arch_x86.ext_dest_id field.
> + */
> +#define LIBXL_HAVE_X86_EST_DEST_ID 1

Did you mean LIBXL_HAVE_X86_EXT_DEST_ID, as the comment has it?

> --- a/tools/libs/light/libxl_types.idl
> +++ b/tools/libs/light/libxl_types.idl
> @@ -648,6 +648,7 @@ libxl_domain_build_info = Struct("domain_build_info",[
>                                 ("vuart", libxl_vuart_type),
>                                ])),
>      ("arch_x86", Struct(None, [("msr_relaxed", libxl_defbool),
> +                               ("ext_dest_id", libxl_defbool),

Let's hope there's not going to appear any other meaning of "dest ID".
I would have suggested to add "apic" to the name, but this would get
it a little longish for my taste.

> --- a/xen/arch/x86/setup.c
> +++ b/xen/arch/x86/setup.c
> @@ -782,6 +782,7 @@ static struct domain *__init create_dom0(const module_t 
> *image,
>  
>          dom0_cfg.arch.emulation_flags |=
>              XEN_X86_EMU_LAPIC | XEN_X86_EMU_IOAPIC | XEN_X86_EMU_VPCI;
> +        dom0_cfg.arch.misc_flags |= XEN_X86_EXT_DEST_ID;
>      }

Without any way to suppress this?

> --- a/xen/include/public/domctl.h
> +++ b/xen/include/public/domctl.h
> @@ -38,7 +38,7 @@
>  #include "hvm/save.h"
>  #include "memory.h"
>  
> -#define XEN_DOMCTL_INTERFACE_VERSION 0x00000014
> +#define XEN_DOMCTL_INTERFACE_VERSION 0x00000015

I'm struggling to figure which binary incompatible change in here
requires this bumping. Does this perhaps belong in a later patch?

Jan