Re: [PATCH v3] self_tests/kvm: sync_regs test for diag318

[Janosch Frank <frankja@linux.ibm.com>]

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On 12/3/20 10:52 PM, Collin Walling wrote:
> The DIAGNOSE 0x0318 instruction, unique to s390x, is a privileged call

s/call/instruction/

> that must be intercepted via SIE, handled in userspace, and the
> information set by the instruction is communicated back to KVM.
> 
> To test the instruction interception, an ad-hoc handler is defined which
> simply has a VM execute the instruction and then userspace will extract
> the necessary info. The handler is defined such that the instruction
> invocation occurs only once. It is up to the caller to determine how the
> info returned by this handler should be used.
> 
> The diag318 info is communicated from userspace to KVM via a sync_regs
> call. This is tested during a sync_regs test, where the diag318 info is
> requested via the handler, then the info is stored in the appropriate
> register in KVM via a sync registers call.
> 
> If KVM does not support diag318, then the tests will print a message
> stating that diag318 was skipped, and the asserts will simply test
> against a value of 0.
> 
> Signed-off-by: Collin Walling <walling@linux.ibm.com>

Acked-by: Janosch Frank <frankja@linux.ibm.com>

Some nits below.

> ---
> 
> v3 changes: no longer testing the reset code, as it is handled
> entirely via userspace. The respective reset tests have been removed
> 
> ---
>  tools/testing/selftests/kvm/Makefile          |  2 +-
>  .../kvm/include/s390x/diag318_test_handler.h  | 13 +++
>  .../kvm/lib/s390x/diag318_test_handler.c      | 82 +++++++++++++++++++
>  tools/testing/selftests/kvm/s390x/resets.c    |  1 +
>  .../selftests/kvm/s390x/sync_regs_test.c      | 16 +++-
>  5 files changed, 112 insertions(+), 2 deletions(-)
>  create mode 100644 tools/testing/selftests/kvm/include/s390x/diag318_test_handler.h
>  create mode 100644 tools/testing/selftests/kvm/lib/s390x/diag318_test_handler.c
> 
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index 3d14ef77755e..426c78449044 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -36,7 +36,7 @@ endif
>  LIBKVM = lib/assert.c lib/elf.c lib/io.c lib/kvm_util.c lib/sparsebit.c lib/test_util.c
>  LIBKVM_x86_64 = lib/x86_64/processor.c lib/x86_64/vmx.c lib/x86_64/svm.c lib/x86_64/ucall.c lib/x86_64/handlers.S
>  LIBKVM_aarch64 = lib/aarch64/processor.c lib/aarch64/ucall.c
> -LIBKVM_s390x = lib/s390x/processor.c lib/s390x/ucall.c
> +LIBKVM_s390x = lib/s390x/processor.c lib/s390x/ucall.c lib/s390x/diag318_test_handler.c
>  
>  TEST_GEN_PROGS_x86_64 = x86_64/cr4_cpuid_sync_test
>  TEST_GEN_PROGS_x86_64 += x86_64/evmcs_test
> diff --git a/tools/testing/selftests/kvm/include/s390x/diag318_test_handler.h b/tools/testing/selftests/kvm/include/s390x/diag318_test_handler.h
> new file mode 100644
> index 000000000000..b0ed71302722
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/include/s390x/diag318_test_handler.h
> @@ -0,0 +1,13 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later
> + *
> + * Test handler for the s390x DIAGNOSE 0x0318 instruction.
> + *
> + * Copyright (C) 2020, IBM
> + */
> +
> +#ifndef SELFTEST_KVM_DIAG318_TEST_HANDLER
> +#define SELFTEST_KVM_DIAG318_TEST_HANDLER
> +
> +uint64_t get_diag318_info(void);
> +
> +#endif
> diff --git a/tools/testing/selftests/kvm/lib/s390x/diag318_test_handler.c b/tools/testing/selftests/kvm/lib/s390x/diag318_test_handler.c
> new file mode 100644
> index 000000000000..1e0b766efeb7
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/lib/s390x/diag318_test_handler.c
> @@ -0,0 +1,82 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Test handler for the s390x DIAGNOSE 0x0318 instruction.
> + *
> + * Copyright (C) 2020, IBM
> + */
> +
> +#include "test_util.h"
> +#include "kvm_util.h"
> +
> +#define VCPU_ID	5

The sync_regs test has the same ID, will this be a problem?

> +
> +#define ICPT_INSTRUCTION	0x04
> +#define IPA0_DIAG		0x8300
> +
> +static void guest_code(void)
> +{
> +	uint64_t diag318_info = 0x12345678;
> +
> +	asm volatile ("diag %0,0,0x318\n" : : "d" (diag318_info));
> +}
> +
> +/*
> + * The DIAGNOSE 0x0318 instruction call must be handled via userspace. As such,
> + * we create an ad-hoc VM here to handle the instruction then extract the
> + * necessary data. It is up to the caller to decide what to do with that data.
> + */
> +static uint64_t diag318_handler(void)
> +{
> +	struct kvm_vm *vm;
> +	struct kvm_run *run;
> +	uint64_t reg;
> +	uint64_t diag318_info;
> +
> +	vm = vm_create_default(VCPU_ID, 0, guest_code);
> +	vcpu_run(vm, VCPU_ID);
> +	run = vcpu_state(vm, VCPU_ID);
> +
> +	TEST_ASSERT(run->exit_reason == KVM_EXIT_S390_SIEIC,
> +		    "DIAGNOSE 0x0318 instruction was not intercepted");
> +	TEST_ASSERT(run->s390_sieic.icptcode == ICPT_INSTRUCTION,
> +		    "Unexpected intercept code: 0x%x", run->s390_sieic.icptcode);
> +	TEST_ASSERT((run->s390_sieic.ipa & 0xff00) == IPA0_DIAG,
> +		    "Unexpected IPA0 code: 0x%x", (run->s390_sieic.ipa & 0xff00));
> +
> +	reg = (run->s390_sieic.ipa & 0x00f0) >> 4;
> +	diag318_info = run->s.regs.gprs[reg];
> +
> +	TEST_ASSERT(diag318_info != 0, "DIAGNOSE 0x0318 info not set");
> +
> +	kvm_vm_free(vm);
> +
> +	return diag318_info;
> +}
> +
> +uint64_t get_diag318_info(void)
> +{
> +	static uint64_t diag318_info;
> +	static bool printed_skip;
> +
> +	/*
> +	 * If KVM does not support diag318, then return 0 to
> +	 * ensure tests do not break.
> +	 */
> +	if (!kvm_check_cap(KVM_CAP_S390_DIAG318)) {
> +		if (!printed_skip) {
> +			fprintf(stdout, "KVM_CAP_S390_DIAG318 not supported. "
> +				"Skipping diag318 test.\n");
> +			printed_skip = true;
> +		}
> +		return 0;
> +	}
> +
> +	/*
> +	 * If a test has previously requested the diag318 info,
> +	 * then don't bother spinning up a temporary VM again.
> +	 */
> +	if (!diag318_info)
> +		diag318_info = diag318_handler();
> +
> +	return diag318_info;
> +}
> diff --git a/tools/testing/selftests/kvm/s390x/resets.c b/tools/testing/selftests/kvm/s390x/resets.c
> index b143db6d8693..b3d7d4ac2d54 100644
> --- a/tools/testing/selftests/kvm/s390x/resets.c
> +++ b/tools/testing/selftests/kvm/s390x/resets.c
> @@ -110,6 +110,7 @@ static void assert_clear(void)
>  
>  	TEST_ASSERT(!memcmp(sync_regs->vrs, regs_null, sizeof(sync_regs->vrs)),
>  		    "vrs0-15 == 0 (sync_regs)");
> +

Whitespace damage

>  }
>  
>  static void assert_initial_noclear(void)
> diff --git a/tools/testing/selftests/kvm/s390x/sync_regs_test.c b/tools/testing/selftests/kvm/s390x/sync_regs_test.c
> index 5731ccf34917..caf7b8859a94 100644
> --- a/tools/testing/selftests/kvm/s390x/sync_regs_test.c
> +++ b/tools/testing/selftests/kvm/s390x/sync_regs_test.c
> @@ -20,6 +20,7 @@
>  
>  #include "test_util.h"
>  #include "kvm_util.h"
> +#include "diag318_test_handler.h"
>  
>  #define VCPU_ID 5
>  
> @@ -70,7 +71,7 @@ static void compare_sregs(struct kvm_sregs *left, struct kvm_sync_regs *right)
>  
>  #undef REG_COMPARE
>  
> -#define TEST_SYNC_FIELDS   (KVM_SYNC_GPRS|KVM_SYNC_ACRS|KVM_SYNC_CRS)
> +#define TEST_SYNC_FIELDS   (KVM_SYNC_GPRS|KVM_SYNC_ACRS|KVM_SYNC_CRS|KVM_SYNC_DIAG318)
>  #define INVALID_SYNC_FIELD 0x80000000
>  
>  int main(int argc, char *argv[])
> @@ -152,6 +153,12 @@ int main(int argc, char *argv[])
>  
>  	run->kvm_valid_regs = TEST_SYNC_FIELDS;
>  	run->kvm_dirty_regs = KVM_SYNC_GPRS | KVM_SYNC_ACRS;
> +
> +	if (get_diag318_info() > 0) {
> +		run->s.regs.diag318 = get_diag318_info();
> +		run->kvm_dirty_regs |= KVM_SYNC_DIAG318;
> +	}
> +
>  	rv = _vcpu_run(vm, VCPU_ID);
>  	TEST_ASSERT(rv == 0, "vcpu_run failed: %d\n", rv);
>  	TEST_ASSERT(run->exit_reason == KVM_EXIT_S390_SIEIC,
> @@ -164,6 +171,9 @@ int main(int argc, char *argv[])
>  	TEST_ASSERT(run->s.regs.acrs[0]  == 1 << 11,
>  		    "acr0 sync regs value incorrect 0x%x.",
>  		    run->s.regs.acrs[0]);
> +	TEST_ASSERT(run->s.regs.diag318 == get_diag318_info(),
> +		    "diag318 sync regs value incorrect 0x%llx.",
> +		    run->s.regs.diag318);
>  
>  	vcpu_regs_get(vm, VCPU_ID, &regs);
>  	compare_regs(&regs, &run->s.regs);
> @@ -177,6 +187,7 @@ int main(int argc, char *argv[])
>  	run->kvm_valid_regs = TEST_SYNC_FIELDS;
>  	run->kvm_dirty_regs = 0;
>  	run->s.regs.gprs[11] = 0xDEADBEEF;
> +	run->s.regs.diag318 = 0x4B1D;
>  	rv = _vcpu_run(vm, VCPU_ID);
>  	TEST_ASSERT(rv == 0, "vcpu_run failed: %d\n", rv);
>  	TEST_ASSERT(run->exit_reason == KVM_EXIT_S390_SIEIC,
> @@ -186,6 +197,9 @@ int main(int argc, char *argv[])
>  	TEST_ASSERT(run->s.regs.gprs[11] != 0xDEADBEEF,
>  		    "r11 sync regs value incorrect 0x%llx.",
>  		    run->s.regs.gprs[11]);
> +	TEST_ASSERT(run->s.regs.diag318 != 0x4B1D,
> +		    "diag318 sync regs value incorrect 0x%llx.",
> +		    run->s.regs.diag318);
>  
>  	kvm_vm_free(vm);
>  
> 


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