KVM: selftests: Consolidate common code for populating ucall struct

Make ucall() a common helper that populates struct ucall, and only calls
into arch code to make the actually call out to userspace.

Rename all arch-specific helpers to make it clear they're arch-specific,
and to avoid collisions with common helpers (one more on its way...)

Add WRITE_ONCE() to stores in ucall() code (as already done to aarch64
code in commit 9e2f6498efbb ("selftests: KVM: Handle compiler
optimizations in ucall")) to prevent clang optimizations breaking ucalls.

Cc: Colton Lewis <[email protected]>
Reviewed-by: Andrew Jones <[email protected]>
Tested-by: Peter Gonda <[email protected]>
Signed-off-by: Sean Christopherson <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

1 files changed, 20 insertions, 0 deletions

diff --git a/tools/testing/selftests/kvm/lib/ucall_common.c b/tools/testing/selftests/kvm/lib/ucall_common.c
new file mode 100644
index 000000000000..2395c7f1d543
--- /dev/null
+++ b/tools/testing/selftests/kvm/lib/ucall_common.c
@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include "kvm_util.h"
+
+void ucall(uint64_t cmd, int nargs, ...)
+{
+	struct ucall uc = {};
+	va_list va;
+	int i;
+
+	WRITE_ONCE(uc.cmd, cmd);
+
+	nargs = min(nargs, UCALL_MAX_ARGS);
+
+	va_start(va, nargs);
+	for (i = 0; i < nargs; ++i)
+		WRITE_ONCE(uc.args[i], va_arg(va, uint64_t));
+	va_end(va);
+
+	ucall_arch_do_ucall((vm_vaddr_t)&uc);
+}