Re: [PATCH 1/6] ARM: kvm: psci: fix handling of unimplemented functions

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On 29/05/15 13:16, Lorenzo Pieralisi wrote:
According to the PSCI specification and the SMC/HVC calling
convention, PSCI function_ids that are not implemented must
return NOT_SUPPORTED as return value.

Current KVM implementation takes an unhandled PSCI function_id
as an error and injects an undefined instruction into the guest
if PSCI implementation is called with a function_id that is not
handled by the resident PSCI version (ie it is not implemented),
which is not the behaviour expected by a guest when calling a
PSCI function_id that is not implemented.

This patch fixes this issue by returning NOT_SUPPORTED whenever
the kvm PSCI call is executed for a function_id that is not
implemented by the PSCI kvm layer.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
Reported-by: Sudeep Holla <sudeep.holla@xxxxxxx>
Cc: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
Cc: Anup Patel <anup.patel@xxxxxxxxxx>
Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
---
  arch/arm/kvm/psci.c | 6 +++---
  1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c
index 7e9398c..ec5943b 100644
--- a/arch/arm/kvm/psci.c
+++ b/arch/arm/kvm/psci.c
@@ -273,7 +273,8 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
  		ret = 0;
  		break;
  	default:
-		return -EINVAL;
+		val = PSCI_RET_NOT_SUPPORTED;
+		break;

IMO we can remove all the other optional non-implemented PSCI functions
(e.g. KVM_PSCI_FN_MIGRATE, KVM_PSCI_FN_CPU_SUSPEND, ..etc) returning
PSCI_RET_NOT_SUPPORTED here as they will be then automatically covered
by default case.

Otherwise looks good to me:
Acked-by: Sudeep Holla <sudeep.holla@xxxxxxx>

Regards,
Sudeep
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