Re: [PATCH 2/7] x86: don't allow Dom0 access to port 92

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

On Thu, May 11, 2023 at 02:05:45PM +0200, Jan Beulich wrote:
> Somewhat like port CF9 this may have a bit controlling the CPU's INIT#
> signal, and it also may have a bit involved in the driving of A20M#.
> Neither of these - just like CF9 - we want to allow Dom0 to drive.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Acked-by: Roger Pau Monné <roger.pau@citrix.com>

I'm kind of concerned that such ports might be used for other stuff
not described in the specifications I'm looking at, I guess we will
find out.

> 
> --- a/xen/arch/x86/dom0_build.c
> +++ b/xen/arch/x86/dom0_build.c
> @@ -500,6 +500,10 @@ int __init dom0_setup_permissions(struct
>      rc |= ioports_deny_access(d, 0x40, 0x43);
>      /* PIT Channel 2 / PC Speaker Control. */
>      rc |= ioports_deny_access(d, 0x61, 0x61);
> +
> +    /* INIT# and alternative A20M# control. */
> +    rc |= ioports_deny_access(d, 0x92, 0x92);

I do wonder whether it would make sense to create an array of [start,
end] IO ports to deny access to, so that we could loop over them and
code a single call to ioports_deny_access().  Maybe that's over
engineering it.

Thanks, Roger.