On 2023-03-28 09:52, Suzuki K Poulose wrote:
On 20/03/2023 22:09, Oliver Upton wrote:
Whelp, the architecture gods have spoken and confirmed that the
function
ID space is common between SMCs and HVCs. Not only that, the
expectation
is that hypervisors handle calls to both SMC and HVC conduits. KVM
recently picked up support for SMCCCs in commit bd36b1a9eb5a ("KVM:
arm64: nv: Handle SMCs taken from virtual EL2") but scoped it only to
a
nested hypervisor.
Let's just open the floodgates and let EL1 access our SMCCC
implementation with the SMC instruction as well.
Signed-off-by: Oliver Upton <oliver.upton@xxxxxxxxx>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
One minor observation below.
---
arch/arm64/kvm/handle_exit.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/arch/arm64/kvm/handle_exit.c
b/arch/arm64/kvm/handle_exit.c
index 5e4f9737cbd5..68f95dcd41a1 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -72,13 +72,15 @@ static int handle_smc(struct kvm_vcpu *vcpu)
*
* We need to advance the PC after the trap, as it would
* otherwise return to the same address...
- *
- * Only handle SMCs from the virtual EL2 with an immediate of zero
and
- * skip it otherwise.
*/
- if (!vcpu_is_el2(vcpu) || kvm_vcpu_hvc_get_imm(vcpu)) {
+ kvm_incr_pc(vcpu);
+
+ /*
+ * SMCs with a nonzero immediate are reserved according to DEN0028E
2.9
+ * "SMC and HVC immediate value".
+ */
+ if (kvm_vcpu_hvc_get_imm(vcpu)) {
vcpu_set_reg(vcpu, 0, ~0UL);
- kvm_incr_pc(vcpu);
return 1;
}
@@ -93,8 +95,6 @@ static int handle_smc(struct kvm_vcpu *vcpu)
if (ret < 0)
vcpu_set_reg(vcpu, 0, ~0UL);
Nothing to do with this patch. But that check above is different
from how we handle HVC. i.e., we return back to guest for HVCs.
But for SMCs, we tend to return "ret" indicating an error (ret < 0).
Do we need to fix that ?
I guess so. It is just that it is practically impossible to get
a negative value at the moment, but it isn't something we should
rely on.
Thanks,
M.
--
Jazz is not dead. It just smells funny...
