Re: [PATCH v5 05/19] arm64: Detect if in a realm and set RIPAS RAM

[Gavin Shan]

On 8/31/24 1:54 AM, Steven Price wrote:
> On 26/08/2024 11:03, Catalin Marinas wrote:
> > On Mon, Aug 19, 2024 at 02:19:10PM +0100, Steven Price wrote:

[...]

> > > +
> > > +void __init arm64_rsi_setup_memory(void)
> > > +{
> > > +	u64 i;
> > > +	phys_addr_t start, end;
> > > +
> > > +	if (!is_realm_world())
> > > +		return;
> > > +
> > > +	/*
> > > +	 * Iterate over the available memory ranges and convert the state to
> > > +	 * protected memory. We should take extra care to ensure that we DO NOT
> > > +	 * permit any "DESTROYED" pages to be converted to "RAM".
> > > +	 *
> > > +	 * BUG_ON is used because if the attempt to switch the memory to
> > > +	 * protected has failed here, then future accesses to the memory are
> > > +	 * simply going to be reflected as a SEA (Synchronous External Abort)
> > > +	 * which we can't handle.  Bailing out early prevents the guest limping
> > > +	 * on and dying later.
> > > +	 */
> > > +	for_each_mem_range(i, &start, &end) {
> > > +		BUG_ON(rsi_set_memory_range_protected_safe(start, end));
> > > +	}
> >
> > Would it help debugging if we print the memory ranges as well rather
> > than just a BUG_ON()?
>
> Yes that would probably be useful - I'll fix that.

One potential issue I'm seeing is WARN_ON() followed by BUG_ON(). They're a bit
duplicate. I would suggest to remove the WARN_ON() and print informative messages
in rsi_set_memory_range().

  setup_arch
  arm64_rsi_setup_memory                    // BUG_ON(error)
  rsi_set_memory_range_protected_safe
  rsi_set_memory_range                      // WARN_ON(error)

Thanks,
Gavin