Re: [PATCH v4 06/21] KVM: arm64: Support SDEI_EVENT_CONTEXT hypercall

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Hi Eric,

On 11/10/21 7:16 PM, Eric Auger wrote:
On 8/15/21 2:13 AM, Gavin Shan wrote:
This supports SDEI_EVENT_CONTEXT hypercall. It's used by the guest
to retrieved the original registers (R0 - R17) in its SDEI event
handler. Those registers can be corrupted during the SDEI event
delivery.

Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
---
  arch/arm64/kvm/sdei.c | 40 ++++++++++++++++++++++++++++++++++++++++
  1 file changed, 40 insertions(+)

diff --git a/arch/arm64/kvm/sdei.c b/arch/arm64/kvm/sdei.c
index b022ce0a202b..b4162efda470 100644
--- a/arch/arm64/kvm/sdei.c
+++ b/arch/arm64/kvm/sdei.c
@@ -270,6 +270,44 @@ static unsigned long kvm_sdei_hypercall_enable(struct kvm_vcpu *vcpu,
  	return ret;
  }
+static unsigned long kvm_sdei_hypercall_context(struct kvm_vcpu *vcpu)
+{
+	struct kvm *kvm = vcpu->kvm;
+	struct kvm_sdei_kvm *ksdei = kvm->arch.sdei;
+	struct kvm_sdei_vcpu *vsdei = vcpu->arch.sdei;
+	struct kvm_sdei_vcpu_regs *regs;
+	unsigned long index = smccc_get_arg1(vcpu);
s/index/param_id to match the spec?

Sure, but "reg_id" seems better here. As the parameter indicates the GPR index
to be fetched on request of the guest kernel.

+	unsigned long ret = SDEI_SUCCESS;
+
+	/* Sanity check */
+	if (!(ksdei && vsdei)) {
+		ret = SDEI_NOT_SUPPORTED;
+		goto out;
+	}
+
+	if (index > ARRAY_SIZE(vsdei->state.critical_regs.regs)) {
+		ret = SDEI_INVALID_PARAMETERS;
+		goto out;
+	}
I would move the above after regs = and use regs there (although the
regs ARRAY_SIZE of both is identifical)

Ok.

+
+	/* Check if the pending event exists */
+	spin_lock(&vsdei->lock);
+	if (!(vsdei->critical_event || vsdei->normal_event)) {
+		ret = SDEI_DENIED;
+		goto unlock;
+	}
+
+	/* Fetch the requested register */
+	regs = vsdei->critical_event ? &vsdei->state.critical_regs :
+				       &vsdei->state.normal_regs;
+	ret = regs->regs[index];
+
+unlock:
+	spin_unlock(&vsdei->lock);
+out:
+	return ret;
+}
+
  int kvm_sdei_hypercall(struct kvm_vcpu *vcpu)
  {
  	u32 func = smccc_get_function(vcpu);
@@ -290,6 +328,8 @@ int kvm_sdei_hypercall(struct kvm_vcpu *vcpu)
  		ret = kvm_sdei_hypercall_enable(vcpu, false);
  		break;
  	case SDEI_1_0_FN_SDEI_EVENT_CONTEXT:
+		ret = kvm_sdei_hypercall_context(vcpu);
+		break;
  	case SDEI_1_0_FN_SDEI_EVENT_COMPLETE:
  	case SDEI_1_0_FN_SDEI_EVENT_COMPLETE_AND_RESUME:
  	case SDEI_1_0_FN_SDEI_EVENT_UNREGISTER:


Thanks,
Gavin

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