Re: [PATCH 8/9] xen: introduce flag when a domain requires cache control

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, May 06, 2025 at 11:20:41AM +0100, Julien Grall wrote:
> Hi Roger,
> 
> On 06/05/2025 09:31, Roger Pau Monne wrote:
> > Such flag is added to the domain create hypercall, and a matching option is
> > added to xl and libxl to set the flag: `cache_control`.  When the flag is
> > set, the domain is allowed the usage of cache control operations.
> 
> Can you clarify whether you are talking about using the hypercall to flush
> the cache or the instructions?

On x86 at least: both hypercall and instructions if possible, since
Xen traps cache flush instructions.  Maybe that's different on ARM.
As said on a previous reply I've assumed that cache_flush_permitted()
was also relevant on ARM, but maybe it's not and domains are
unconditionally allowed execution of cache control instructions and
hypercalls.

Thanks, Roger.