Hi David,
On 2020-12-29 16:00, David Brazdil wrote:
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@xxxxxxxxxx>
---
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:
Thanks for having tracked this.
I wonder whether we should also taint the kernel in this case,
because this is completely unexpected, and a major spec violation.
Ideally, we'd be able to detect this case and prevent pKVM from
getting initialised at all, but I guess there is no way to detect
the sucker without ... calling SYSTEM_RESET?
M.
--
Jazz is not dead. It just smells funny...
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