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 9e2f649 ("selftests: KVM: Handle compiler
optimizations in ucall")) to prevent clang optimizations breaking ucalls.

Cc: Colton Lewis <coltonlewis@google.com>
Reviewed-by: Andrew Jones <andrew.jones@linux.dev>
Tested-by: Peter Gonda <pgonda@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20221006003409.649993-2-seanjc@google.com

tools/testing/selftests/kvm/Makefile

@@ -47,6 +47,7 @@ LIBKVM += lib/memstress.c
 LIBKVM += lib/rbtree.c
 LIBKVM += lib/sparsebit.c
 LIBKVM += lib/test_util.c
+LIBKVM += lib/ucall_common.c
 
 LIBKVM_STRING += lib/string_override.c
 

tools/testing/selftests/kvm/include/ucall_common.h

@@ -24,10 +24,27 @@ struct ucall {
 	uint64_t args[UCALL_MAX_ARGS];
 };
 
-void ucall_init(struct kvm_vm *vm, void *arg);
-void ucall_uninit(struct kvm_vm *vm);
+void ucall_arch_init(struct kvm_vm *vm, void *arg);
+void ucall_arch_uninit(struct kvm_vm *vm);
+void ucall_arch_do_ucall(vm_vaddr_t uc);
+uint64_t ucall_arch_get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc);
+
 void ucall(uint64_t cmd, int nargs, ...);
-uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc);
+
+static inline void ucall_init(struct kvm_vm *vm, void *arg)
+{
+	ucall_arch_init(vm, arg);
+}
+
+static inline void ucall_uninit(struct kvm_vm *vm)
+{
+	ucall_arch_uninit(vm);
+}
+
+static inline uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
+{
+	return ucall_arch_get_ucall(vcpu, uc);
+}
 
 #define GUEST_SYNC_ARGS(stage, arg1, arg2, arg3, arg4)	\
 				ucall(UCALL_SYNC, 6, "hello", stage, arg1, arg2, arg3, arg4)

tools/testing/selftests/kvm/lib/aarch64/ucall.c

@@ -21,7 +21,7 @@ static bool ucall_mmio_init(struct kvm_vm *vm, vm_paddr_t gpa)
 	return true;
 }
 
-void ucall_init(struct kvm_vm *vm, void *arg)
+void ucall_arch_init(struct kvm_vm *vm, void *arg)
 {
 	vm_paddr_t gpa, start, end, step, offset;
 	unsigned int bits;
@@ -64,30 +64,18 @@ void ucall_init(struct kvm_vm *vm, void *arg)
 	TEST_FAIL("Can't find a ucall mmio address");
 }
 
-void ucall_uninit(struct kvm_vm *vm)
+void ucall_arch_uninit(struct kvm_vm *vm)
 {
 	ucall_exit_mmio_addr = 0;
 	sync_global_to_guest(vm, ucall_exit_mmio_addr);
 }
 
-void ucall(uint64_t cmd, int nargs, ...)
+void ucall_arch_do_ucall(vm_vaddr_t uc)
 {
-	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);
-
-	WRITE_ONCE(*ucall_exit_mmio_addr, (vm_vaddr_t)&uc);
+	WRITE_ONCE(*ucall_exit_mmio_addr, uc);
 }
 
-uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
+uint64_t ucall_arch_get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
 {
 	struct kvm_run *run = vcpu->run;
 	struct ucall ucall = {};

tools/testing/selftests/kvm/lib/riscv/ucall.c

@@ -10,11 +10,11 @@
 #include "kvm_util.h"
 #include "processor.h"
 
-void ucall_init(struct kvm_vm *vm, void *arg)
+void ucall_arch_init(struct kvm_vm *vm, void *arg)
 {
 }
 
-void ucall_uninit(struct kvm_vm *vm)
+void ucall_arch_uninit(struct kvm_vm *vm)
 {
 }
 
@@ -44,27 +44,14 @@ struct sbiret sbi_ecall(int ext, int fid, unsigned long arg0,
 	return ret;
 }
 
-void ucall(uint64_t cmd, int nargs, ...)
+void ucall_arch_do_ucall(vm_vaddr_t uc)
 {
-	struct ucall uc = {
-		.cmd = cmd,
-	};
-	va_list va;
-	int i;
-
-	nargs = min(nargs, UCALL_MAX_ARGS);
-
-	va_start(va, nargs);
-	for (i = 0; i < nargs; ++i)
-		uc.args[i] = va_arg(va, uint64_t);
-	va_end(va);
-
 	sbi_ecall(KVM_RISCV_SELFTESTS_SBI_EXT,
 		  KVM_RISCV_SELFTESTS_SBI_UCALL,
-		  (vm_vaddr_t)&uc, 0, 0, 0, 0, 0);
+		  uc, 0, 0, 0, 0, 0);
 }
 
-uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
+uint64_t ucall_arch_get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
 {
 	struct kvm_run *run = vcpu->run;
 	struct ucall ucall = {};

tools/testing/selftests/kvm/lib/s390x/ucall.c

@@ -6,34 +6,21 @@
  */
 #include "kvm_util.h"
 
-void ucall_init(struct kvm_vm *vm, void *arg)
+void ucall_arch_init(struct kvm_vm *vm, void *arg)
 {
 }
 
-void ucall_uninit(struct kvm_vm *vm)
+void ucall_arch_uninit(struct kvm_vm *vm)
 {
 }
 
-void ucall(uint64_t cmd, int nargs, ...)
+void ucall_arch_do_ucall(vm_vaddr_t uc)
 {
-	struct ucall uc = {
-		.cmd = cmd,
-	};
-	va_list va;
-	int i;
-
-	nargs = min(nargs, UCALL_MAX_ARGS);
-
-	va_start(va, nargs);
-	for (i = 0; i < nargs; ++i)
-		uc.args[i] = va_arg(va, uint64_t);
-	va_end(va);
-
 	/* Exit via DIAGNOSE 0x501 (normally used for breakpoints) */
-	asm volatile ("diag 0,%0,0x501" : : "a"(&uc) : "memory");
+	asm volatile ("diag 0,%0,0x501" : : "a"(uc) : "memory");
 }
 
-uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
+uint64_t ucall_arch_get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
 {
 	struct kvm_run *run = vcpu->run;
 	struct ucall ucall = {};

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);
+}

tools/testing/selftests/kvm/lib/x86_64/ucall.c

@@ -8,34 +8,21 @@
 
 #define UCALL_PIO_PORT ((uint16_t)0x1000)
 
-void ucall_init(struct kvm_vm *vm, void *arg)
+void ucall_arch_init(struct kvm_vm *vm, void *arg)
 {
 }
 
-void ucall_uninit(struct kvm_vm *vm)
+void ucall_arch_uninit(struct kvm_vm *vm)
 {
 }
 
-void ucall(uint64_t cmd, int nargs, ...)
+void ucall_arch_do_ucall(vm_vaddr_t uc)
 {
-	struct ucall uc = {
-		.cmd = cmd,
-	};
-	va_list va;
-	int i;
-
-	nargs = min(nargs, UCALL_MAX_ARGS);
-
-	va_start(va, nargs);
-	for (i = 0; i < nargs; ++i)
-		uc.args[i] = va_arg(va, uint64_t);
-	va_end(va);
-
 	asm volatile("in %[port], %%al"
-		: : [port] "d" (UCALL_PIO_PORT), "D" (&uc) : "rax", "memory");
+		: : [port] "d" (UCALL_PIO_PORT), "D" (uc) : "rax", "memory");
 }
 
-uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
+uint64_t ucall_arch_get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
 {
 	struct kvm_run *run = vcpu->run;
 	struct ucall ucall = {};