[PATCH] KVM: arm64: Allow PSCI SYSTEM_OFF/RESET to return

David Brazdil
2020-12-29T16:02:44Z

The KVM/arm64 PSCI relay assumes that SYSTEM_OFF and SYSTEM_RESET should
not return, as dictated by the PSCI spec. However, there is firmware out
there which breaks this assumption, leading to a hyp panic. Make KVM
more robust to broken firmware by allowing these to return.

Signed-off-by: David Brazdil <dbrazdil@google.com>
---
arch/arm64/kvm/hyp/nvhe/psci-relay.c | 13 +++++--------
1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/psci-relay.c b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
index e3947846ffcb..8e7128cb7667 100644
--- a/arch/arm64/kvm/hyp/nvhe/psci-relay.c
+++ b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
@@ -77,12 +77,6 @@ static unsigned long psci_forward(struct kvm_cpu_context *host_ctxt)
cpu_reg(host_ctxt, 2), cpu_reg(host_ctxt, 3));
}

-static __noreturn unsigned long psci_forward_noreturn(struct kvm_cpu_context *host_ctxt)
-{
- psci_forward(host_ctxt);
- hyp_panic(); /* unreachable */
-}
-
static unsigned int find_cpu_id(u64 mpidr)
{
unsigned int i;
@@ -251,10 +245,13 @@ static unsigned long psci_0_2_handler(u64 func_id, struct kvm_cpu_context *host_
case PSCI_0_2_FN_MIGRATE_INFO_TYPE:
case PSCI_0_2_FN64_MIGRATE_INFO_UP_CPU:
return psci_forward(host_ctxt);
+ /*
+ * SYSTEM_OFF/RESET should not return according to the spec.
+ * Allow it so as to stay robust to broken firmware.
+ */
case PSCI_0_2_FN_SYSTEM_OFF:
case PSCI_0_2_FN_SYSTEM_RESET:
- psci_forward_noreturn(host_ctxt);
- unreachable();
+ return psci_forward(host_ctxt);
case PSCI_0_2_FN64_CPU_SUSPEND:
return psci_cpu_suspend(func_id, host_ctxt);
case PSCI_0_2_FN64_CPU_ON:
--
2.29.2.729.g45daf8777d-goog