[PATCH 04/16] KVM: selftests: Export the ucall pool's guest physical address

[Fuad Tabba <fuad.tabba@linux.dev>]

A protected guest's memory is private until the guest itself shares it,
so the guest has to share the ucall pool before its first ucall. The
host can't do that for it. Only the guest's copy of ucall_pool holds the
pool's address.

Add get_ucall_pool_gpa(), which reads that copy, so that the host can
pass the address to the guest.

Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
---
 tools/testing/selftests/kvm/include/ucall_common.h | 1 +
 tools/testing/selftests/kvm/lib/ucall_common.c     | 9 ++++++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/kvm/include/ucall_common.h b/tools/testing/selftests/kvm/include/ucall_common.h
index cbdcb0a50c4f9..3a6cdf9aa0464 100644
--- a/tools/testing/selftests/kvm/include/ucall_common.h
+++ b/tools/testing/selftests/kvm/include/ucall_common.h
@@ -41,6 +41,7 @@ __printf(5, 6) void ucall_assert(u64 cmd, const char *exp,
 u64 get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc);
 void ucall_init(struct kvm_vm *vm, gpa_t mmio_gpa);
 int ucall_nr_pages_required(u64 page_size);
+gpa_t get_ucall_pool_gpa(struct kvm_vm *vm);
 
 /*
  * Perform userspace call without any associated data.  This bare call avoids
diff --git a/tools/testing/selftests/kvm/lib/ucall_common.c b/tools/testing/selftests/kvm/lib/ucall_common.c
index 029ce21f9f2fa..aa1f0f92c6d1d 100644
--- a/tools/testing/selftests/kvm/lib/ucall_common.c
+++ b/tools/testing/selftests/kvm/lib/ucall_common.c
@@ -21,10 +21,17 @@ int ucall_nr_pages_required(u64 page_size)
 
 /*
  * ucall_pool holds per-VM values (global data is duplicated by each VM), it
- * must not be accessed from host code.
+ * must not be accessed from host code. The host reads only a VM's copy.
  */
 static struct ucall_header *ucall_pool;
 
+gpa_t get_ucall_pool_gpa(struct kvm_vm *vm)
+{
+	struct ucall_header **pool = addr_gva2hva(vm, (gva_t)&ucall_pool);
+
+	return addr_gva2gpa(vm, (gva_t)*pool);
+}
+
 void ucall_init(struct kvm_vm *vm, gpa_t mmio_gpa)
 {
 	struct ucall_header *hdr;
-- 
2.47.3