Re: [PATCH v8 16/43] arm64: RME: Handle realm enter/exit

[Suzuki K Poulose]

On 02/06/2025 16:14, Steven Price wrote:
> On 29/05/2025 05:52, Emi Kisanuki (Fujitsu) wrote:
> > Hello, I comment below.
>
> Hi Emi,
>
> > > Subject: [PATCH v8 16/43] arm64: RME: Handle realm enter/exit
> > >
> > > Entering a realm is done using a SMC call to the RMM. On exit the exit-codes
> > > need to be handled slightly differently to the normal KVM path so define our own
> > > functions for realm enter/exit and hook them in if the guest is a realm guest.
> > >
> > > Signed-off-by: Steven Price <steven.price@xxxxxxx>
> > > ---
>
> [..]
>
> > > +/*
> > > + * Return > 0 to return to guest, < 0 on error, 0 (and set exit_reason)
> > > +on
> > > + * proper exit to userspace.
> > > + */
> > > +int handle_rec_exit(struct kvm_vcpu *vcpu, int rec_run_ret) {
> > > +	struct realm_rec *rec = &vcpu->arch.rec;
> > > +	u8 esr_ec = ESR_ELx_EC(rec->run->exit.esr);
> > > +	unsigned long status, index;
> > > +
> > > +	status = RMI_RETURN_STATUS(rec_run_ret);
> > > +	index = RMI_RETURN_INDEX(rec_run_ret);
> > > +
> > > +	/*
> > > +	 * If a PSCI_SYSTEM_OFF request raced with a vcpu executing, we
> > > might
> > > +	 * see the following status code and index indicating an attempt to run
> > > +	 * a REC when the RD state is SYSTEM_OFF.  In this case, we just need
> > > to
> > > +	 * return to user space which can deal with the system event or will try
> > > +	 * to run the KVM VCPU again, at which point we will no longer attempt
> > > +	 * to enter the Realm because we will have a sleep request pending on
> > > +	 * the VCPU as a result of KVM's PSCI handling.
> > > +	 */
> > > +	if (status == RMI_ERROR_REALM && index == 1) {
> > > +		vcpu->run->exit_reason = KVM_EXIT_UNKNOWN;
> > > +		return 0;
> > > +	}
> > Running kvm-unit-tests-cca selftest(smp) test in quick succession may trigger these conditions, resulting in the following error logs.
> >   Error: KVM exit reason: 0 ("KVM_EXIT_UNKNOWN")
> >
> > Since KVM_EXIT_UNKNOWN is used when no specific exit reason applies, I think it would be better to make it identifiable as an error.
> > How about adding and setting a new ARM64 exit_reason value to indicate that the PSCI_SYSTEM_OFF request is conflicting with a running vcpu?
>
> Aneesh pointed this out to me off-list. We agreed that KVM_EXIT_SHUTDOWN
> was more appropriate here. I'll make the change for v9.

Sounds good to me

Cheers
Suzuki