[RFC PATCH kvmtool v1 30/32] pkvm: Enable exit hypercall capability if supported

[Fuad Tabba <tabba@google.com>]

This hypercall allows the guest to communicate with the host via
the new exit type. It will be used in future patches to
communicate guest-triggered change of memory sharing status with
the host/vmm (kvmtool).

Signed-off-by: Fuad Tabba <tabba@google.com>
---
 arm/aarch32/include/kvm/kvm-arch.h |  1 +
 arm/aarch64/include/kvm/kvm-arch.h |  1 +
 arm/aarch64/kvm.c                  | 23 +++++++++++++++++++++++
 arm/kvm-cpu.c                      | 10 ++++++++++
 arm/kvm.c                          |  1 +
 5 files changed, 36 insertions(+)

diff --git a/arm/aarch32/include/kvm/kvm-arch.h b/arm/aarch32/include/kvm/kvm-arch.h
index 467fb09..5666f2f 100644
--- a/arm/aarch32/include/kvm/kvm-arch.h
+++ b/arm/aarch32/include/kvm/kvm-arch.h
@@ -7,6 +7,7 @@
 
 struct kvm;
 static inline void kvm__arch_enable_mte(struct kvm *kvm) {}
+static inline void kvm__arch_enable_exit_hypcall(struct kvm *kvm) {}
 
 #define MAX_PAGE_SIZE	SZ_4K
 
diff --git a/arm/aarch64/include/kvm/kvm-arch.h b/arm/aarch64/include/kvm/kvm-arch.h
index 02d09a4..9af002b 100644
--- a/arm/aarch64/include/kvm/kvm-arch.h
+++ b/arm/aarch64/include/kvm/kvm-arch.h
@@ -7,6 +7,7 @@ struct kvm;
 unsigned long long kvm__arch_get_kern_offset(struct kvm *kvm, int fd);
 int kvm__arch_get_ipa_limit(struct kvm *kvm);
 void kvm__arch_enable_mte(struct kvm *kvm);
+void kvm__arch_enable_exit_hypcall(struct kvm *kvm);
 
 #define MAX_PAGE_SIZE	SZ_64K
 
diff --git a/arm/aarch64/kvm.c b/arm/aarch64/kvm.c
index f65c9c1..604a5e8 100644
--- a/arm/aarch64/kvm.c
+++ b/arm/aarch64/kvm.c
@@ -163,3 +163,26 @@ void kvm__arch_enable_mte(struct kvm *kvm)
 
 	pr_debug("MTE capability enabled");
 }
+
+void kvm__arch_enable_exit_hypcall(struct kvm *kvm)
+{
+	struct kvm_enable_cap cap = {
+		.cap = KVM_CAP_EXIT_HYPERCALL,
+		.args[0] = KVM_EXIT_HYPERCALL_VALID_MASK,
+	};
+
+	if (kvm->cfg.arch.aarch32_guest) {
+		pr_debug("EXIT HYPERCALL is incompatible with AArch32");
+		return;
+	}
+
+	if (!kvm__supports_extension(kvm, KVM_CAP_EXIT_HYPERCALL)) {
+		pr_debug("EXIT HYPERCALL capability not available");
+		return;
+	}
+
+	if (ioctl(kvm->vm_fd, KVM_ENABLE_CAP, &cap))
+		die_perror("KVM_ENABLE_CAP(KVM_CAP_EXIT_HYPERCALL)");
+
+	pr_debug("EXIT capability enabled");
+}
diff --git a/arm/kvm-cpu.c b/arm/kvm-cpu.c
index 98bc5fd..cb5a92a 100644
--- a/arm/kvm-cpu.c
+++ b/arm/kvm-cpu.c
@@ -146,6 +146,16 @@ void kvm_cpu__delete(struct kvm_cpu *vcpu)
 
 bool kvm_cpu__handle_exit(struct kvm_cpu *vcpu)
 {
+	switch (vcpu->kvm_run->exit_reason) {
+	case KVM_EXIT_HYPERCALL:
+		pr_warning("Unhandled exit hypercall: 0x%llx, 0x%llx, 0x%llx, 0x%llx",
+			   vcpu->kvm_run->hypercall.nr,
+			   vcpu->kvm_run->hypercall.ret,
+			   vcpu->kvm_run->hypercall.args[0],
+			   vcpu->kvm_run->hypercall.args[1]);
+		return true;
+	}
+
 	return false;
 }
 
diff --git a/arm/kvm.c b/arm/kvm.c
index 094fbe4..f4b0247 100644
--- a/arm/kvm.c
+++ b/arm/kvm.c
@@ -84,6 +84,7 @@ void kvm__arch_init(struct kvm *kvm)
 		die("Failed to create virtual GIC");
 
 	kvm__arch_enable_mte(kvm);
+	kvm__arch_enable_exit_hypcall(kvm);
 }
 
 #define FDT_ALIGN	SZ_2M
-- 
2.39.0.rc0.267.gcb52ba06e7-goog