KVM: selftests: Enable ucall and dirty_log_test on s390x

Implement the ucall() interface on s390x to be able to use the dirty_log_test KVM selftest on s390x, too.

v3:
- Fix compilation issue on aarch64 (thanks to Andrew for testing it!)
- Added Reviewed-bys

v2:
- Split up ucall.c into architecture specific files
- Removed some #ifdef __s390x__ in the dirty_log patch

Thomas Huth (3):
KVM: selftests: Split ucall.c into architecture specific files
KVM: selftests: Implement ucall() for s390x
KVM: selftests: Enable dirty_log_test on s390x

 tools/testing/selftests/kvm/Makefile          |   9 +-
 tools/testing/selftests/kvm/dirty_log_test.c  |  61 ++++++-
 .../testing/selftests/kvm/include/kvm_util.h  |   8 +-
 .../testing/selftests/kvm/lib/aarch64/ucall.c | 112 +++++++++++++
 tools/testing/selftests/kvm/lib/s390x/ucall.c |  56 +++++++
 tools/testing/selftests/kvm/lib/ucall.c       | 157 ------------------
 .../testing/selftests/kvm/lib/x86_64/ucall.c  |  56 +++++++
 .../selftests/kvm/s390x/sync_regs_test.c      |   6 +-
 8 files changed, 287 insertions(+), 178 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/lib/aarch64/ucall.c
 create mode 100644 tools/testing/selftests/kvm/lib/s390x/ucall.c
 delete mode 100644 tools/testing/selftests/kvm/lib/ucall.c
 create mode 100644 tools/testing/selftests/kvm/lib/x86_64/ucall.c

2.21.0

The way we exit from a guest to userspace is very specific to the
architecture: On x86, we use PIO, on aarch64 we are using MMIO and on s390x we're going to use an instruction instead. The possibility to select a type via the ucall_type_t enum is currently also completely unused, so the code in ucall.c currently looks more complex than required. Let's split this up into architecture specific ucall.c files instead, so we can get rid of the #ifdefs and the unnecessary ucall_type_t handling.

---
 tools/testing/selftests/kvm/Makefile          |   6 +-
 tools/testing/selftests/kvm/dirty_log_test.c  |   2 +-
 .../testing/selftests/kvm/include/kvm_util.h  |   8 +-
 .../testing/selftests/kvm/lib/aarch64/ucall.c | 112 +++++++++++++
 tools/testing/selftests/kvm/lib/ucall.c       | 157 ------------------
 .../testing/selftests/kvm/lib/x86_64/ucall.c  |  56 +++++++
 6 files changed, 173 insertions(+), 168 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/lib/aarch64/ucall.c
 delete mode 100644 tools/testing/selftests/kvm/lib/ucall.c
 create mode 100644 tools/testing/selftests/kvm/lib/x86_64/ucall.c

index ba7849751989..a51e3b83df40 100644
@@ -7,9 +7,9 @@ top_srcdir = ../../../..
 KSFT_KHDR_INSTALL := 1
 UNAME_M := $(shell uname -m)
 
-LIBKVM = lib/assert.c lib/elf.c lib/io.c lib/kvm_util.c lib/ucall.c lib/sparsebit.c
-LIBKVM_x86_64 = lib/x86_64/processor.c lib/x86_64/vmx.c
-LIBKVM_aarch64 = lib/aarch64/processor.c
+LIBKVM = lib/assert.c lib/elf.c lib/io.c lib/kvm_util.c lib/sparsebit.c
+LIBKVM_x86_64 = lib/x86_64/processor.c lib/x86_64/vmx.c lib/x86_64/ucall.c
+LIBKVM_aarch64 = lib/aarch64/processor.c lib/aarch64/ucall.c
 LIBKVM_s390x = lib/s390x/processor.c
 
 TEST_GEN_PROGS_x86_64 = x86_64/cr4_cpuid_sync_test

index ceb52b952637..5d5ae1be4984 100644
@@ -337,7 +337,7 @@ static void run_test(enum vm_guest_mode mode, unsigned long iterations,
 	vcpu_set_cpuid(vm, VCPU_ID, kvm_get_supported_cpuid());
 #endif
 #ifdef __aarch64__
-	ucall_init(vm, UCALL_MMIO, NULL);
+	ucall_init(vm, NULL);
 #endif
 
 	/* Export the shared variables to the guest */

index e0e66b115ef2..5463b7896a0a 100644
@@ -165,12 +165,6 @@ int vm_create_device(struct kvm_vm *vm, struct kvm_create_device *cd);
 	memcpy(&(g), _p, sizeof(g));				\
 })
 
-/* ucall implementation types */
-typedef enum {
-	UCALL_PIO,
-	UCALL_MMIO,
-} ucall_type_t;
-
 /* Common ucalls */
 enum {
 	UCALL_NONE,

@@ -186,7 +180,7 @@ struct ucall {
 	uint64_t args[UCALL_MAX_ARGS];
 };
 
-void ucall_init(struct kvm_vm *vm, ucall_type_t type, void *arg);
+void ucall_init(struct kvm_vm *vm, void *arg);
 void ucall_uninit(struct kvm_vm *vm);
 void ucall(uint64_t cmd, int nargs, ...);
 uint64_t get_ucall(struct kvm_vm *vm, uint32_t vcpu_id, struct ucall *uc);

2.21.0

On s390x, we can neither exit via PIO nor MMIO, but have to use an instruction like DIAGNOSE. Now that ucall() is implemented, we can use it in the sync_reg_test on s390x, too.

---
 tools/testing/selftests/kvm/Makefile          |  2 +-
 tools/testing/selftests/kvm/lib/s390x/ucall.c | 56 +++++++++++++++++++
 .../selftests/kvm/s390x/sync_regs_test.c      |  6 +-
 3 files changed, 61 insertions(+), 3 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/lib/s390x/ucall.c

index a51e3b83df40..75ea1ecbf85a 100644
@@ -10,7 +10,7 @@ UNAME_M := $(shell uname -m)
 LIBKVM = lib/assert.c lib/elf.c lib/io.c lib/kvm_util.c lib/sparsebit.c
 LIBKVM_x86_64 = lib/x86_64/processor.c lib/x86_64/vmx.c lib/x86_64/ucall.c
 LIBKVM_aarch64 = lib/aarch64/processor.c lib/aarch64/ucall.c
-LIBKVM_s390x = lib/s390x/processor.c
+LIBKVM_s390x = lib/s390x/processor.c lib/s390x/ucall.c
 
 TEST_GEN_PROGS_x86_64 = x86_64/cr4_cpuid_sync_test
 TEST_GEN_PROGS_x86_64 += x86_64/evmcs_test

index e85ff0d69548..bbc93094519b 100644
@@ -25,9 +25,11 @@
 
 static void guest_code(void)
 {
+	register u64 stage asm("11") = 0;
+
 	for (;;) {
-		asm volatile ("diag 0,0,0x501");
-		asm volatile ("ahi 11,1");
+		GUEST_SYNC(0);
+		asm volatile ("ahi %0,1" : : "r"(stage));
 	}
 }
 

2.21.0

To run the dirty_log_test on s390x, we have to make sure that we access the dirty log bitmap with little endian byte ordering and we have to properly align the memslot of the guest. Also all dirty bits of a segment are set once on s390x when one of the pages of a segment are written to for the first time, so we have to make sure that we touch all pages during the first iteration to keep the test in sync here. DEFAULT_GUEST_TEST_MEM needs an adjustment, too. On some s390x distributions, the ELF binary is linked to address 0x80000000, so we have to avoid that our test region overlaps into this area. 0xc0000000 seems to be a good alternative that should work on x86 and aarch64, too.

---
 tools/testing/selftests/kvm/Makefile         |  1 +
 tools/testing/selftests/kvm/dirty_log_test.c | 59 +++++++++++++++++---
 2 files changed, 53 insertions(+), 7 deletions(-)

index 75ea1ecbf85a..1b48a94b4350 100644
@@ -33,6 +33,7 @@ TEST_GEN_PROGS_aarch64 += dirty_log_test
 TEST_GEN_PROGS_aarch64 += kvm_create_max_vcpus
 
 TEST_GEN_PROGS_s390x += s390x/sync_regs_test
+TEST_GEN_PROGS_s390x += dirty_log_test
 TEST_GEN_PROGS_s390x += kvm_create_max_vcpus
 
 TEST_GEN_PROGS += $(TEST_GEN_PROGS_$(UNAME_M))

2.21.0

Paolo, I guess you do not mind if I carry patch 1 also via the s390x tree?

Thanks, all applied

Sure,

Paolo