Re: [PATCH v7 12/12] KVM: selftests: aarch64: vPMU register test for unimplemented counters

[Eric Auger]

Hi Raghavendra,

On 10/10/23 01:08, Raghavendra Rao Ananta wrote:
> From: Reiji Watanabe <reijiw@xxxxxxxxxx>
> 
> Add a new test case to the vpmu_counter_access test to check
> if PMU registers or their bits for unimplemented counters are not
> accessible or are RAZ, as expected.
> 
> Signed-off-by: Reiji Watanabe <reijiw@xxxxxxxxxx>
> Signed-off-by: Raghavendra Rao Ananta <rananta@xxxxxxxxxx>
> ---
>  .../kvm/aarch64/vpmu_counter_access.c         | 95 +++++++++++++++++--
>  .../selftests/kvm/include/aarch64/processor.h |  1 +
>  2 files changed, 87 insertions(+), 9 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/aarch64/vpmu_counter_access.c b/tools/testing/selftests/kvm/aarch64/vpmu_counter_access.c
> index e92af3c0db03..788386ac0894 100644
> --- a/tools/testing/selftests/kvm/aarch64/vpmu_counter_access.c
> +++ b/tools/testing/selftests/kvm/aarch64/vpmu_counter_access.c
> @@ -5,8 +5,8 @@
>   * Copyright (c) 2022 Google LLC.
>   *
>   * This test checks if the guest can see the same number of the PMU event
> - * counters (PMCR_EL0.N) that userspace sets, and if the guest can access
> - * those counters.
> + * counters (PMCR_EL0.N) that userspace sets, if the guest can access
> + * those counters, and if the guest cannot access any other counters.
I would suggest: if the guest is prevented from accessing any other counters
>   * This test runs only when KVM_CAP_ARM_PMU_V3 is supported on the host.
>   */
>  #include <kvm_util.h>
> @@ -131,9 +131,9 @@ static void write_pmevtypern(int n, unsigned long val)
>  }
>  
>  /*
> - * The pmc_accessor structure has pointers to PMEVT{CNTR,TYPER}<n>_EL0
> + * The pmc_accessor structure has pointers to PMEV{CNTR,TYPER}<n>_EL0
>   * accessors that test cases will use. Each of the accessors will
> - * either directly reads/writes PMEVT{CNTR,TYPER}<n>_EL0
> + * either directly reads/writes PMEV{CNTR,TYPER}<n>_EL0
I guess this should belong to the previous patch?
>   * (i.e. {read,write}_pmev{cnt,type}rn()), or reads/writes them through
>   * PMXEV{CNTR,TYPER}_EL0 (i.e. {read,write}_sel_ev{cnt,type}r()).
>   *
> @@ -291,25 +291,85 @@ static void test_access_pmc_regs(struct pmc_accessor *acc, int pmc_idx)
>  		       pmc_idx, PMC_ACC_TO_IDX(acc), read_data, write_data);
>  }
>  
> +#define INVALID_EC	(-1ul)
> +uint64_t expected_ec = INVALID_EC;
> +uint64_t op_end_addr;
> +
>  static void guest_sync_handler(struct ex_regs *regs)
>  {
>  	uint64_t esr, ec;
>  
>  	esr = read_sysreg(esr_el1);
>  	ec = (esr >> ESR_EC_SHIFT) & ESR_EC_MASK;
> -	__GUEST_ASSERT(0, "PC: 0x%lx; ESR: 0x%lx; EC: 0x%lx", regs->pc, esr, ec);
> +
> +	__GUEST_ASSERT(op_end_addr && (expected_ec == ec),
> +			"PC: 0x%lx; ESR: 0x%lx; EC: 0x%lx; EC expected: 0x%lx",
> +			regs->pc, esr, ec, expected_ec);
> +
> +	/* Will go back to op_end_addr after the handler exits */
> +	regs->pc = op_end_addr;
> +
> +	/*
> +	 * Clear op_end_addr, and setting expected_ec to INVALID_EC
and set
> +	 * as a sign that an exception has occurred.
> +	 */
> +	op_end_addr = 0;
> +	expected_ec = INVALID_EC;
> +}
> +
> +/*
> + * Run the given operation that should trigger an exception with the
> + * given exception class. The exception handler (guest_sync_handler)
> + * will reset op_end_addr to 0, and expected_ec to INVALID_EC, and
> + * will come back to the instruction at the @done_label.
> + * The @done_label must be a unique label in this test program.
> + */
> +#define TEST_EXCEPTION(ec, ops, done_label)		\
> +{							\
> +	extern int done_label;				\
> +							\
> +	WRITE_ONCE(op_end_addr, (uint64_t)&done_label);	\
> +	GUEST_ASSERT(ec != INVALID_EC);			\
> +	WRITE_ONCE(expected_ec, ec);			\
> +	dsb(ish);					\
> +	ops;						\
> +	asm volatile(#done_label":");			\
> +	GUEST_ASSERT(!op_end_addr);			\
> +	GUEST_ASSERT(expected_ec == INVALID_EC);	\
> +}
> +
> +/*
> + * Tests for reading/writing registers for the unimplemented event counter
> + * specified by @pmc_idx (>= PMCR_EL0.N).
> + */
> +static void test_access_invalid_pmc_regs(struct pmc_accessor *acc, int pmc_idx)
> +{
> +	/*
> +	 * Reading/writing the event count/type registers should cause
> +	 * an UNDEFINED exception.
> +	 */
> +	TEST_EXCEPTION(ESR_EC_UNKNOWN, acc->read_cntr(pmc_idx), inv_rd_cntr);
> +	TEST_EXCEPTION(ESR_EC_UNKNOWN, acc->write_cntr(pmc_idx, 0), inv_wr_cntr);
> +	TEST_EXCEPTION(ESR_EC_UNKNOWN, acc->read_typer(pmc_idx), inv_rd_typer);
> +	TEST_EXCEPTION(ESR_EC_UNKNOWN, acc->write_typer(pmc_idx, 0), inv_wr_typer);
> +	/*
> +	 * The bit corresponding to the (unimplemented) counter in
> +	 * {PMCNTEN,PMOVS}{SET,CLR}_EL1 registers should be RAZ.
{PMCNTEN,PMINTEN,PMOVS}{SET,CLR}
> +	 */
> +	test_bitmap_pmu_regs(pmc_idx, 1);
> +	test_bitmap_pmu_regs(pmc_idx, 0);
>  }
>  
>  /*
>   * The guest is configured with PMUv3 with @expected_pmcr_n number of
>   * event counters.
>   * Check if @expected_pmcr_n is consistent with PMCR_EL0.N, and
> - * if reading/writing PMU registers for implemented counters can work
> - * as expected.
> + * if reading/writing PMU registers for implemented or unimplemented
> + * counters can work as expected.
>   */
>  static void guest_code(uint64_t expected_pmcr_n)
>  {
> -	uint64_t pmcr, pmcr_n;
> +	uint64_t pmcr, pmcr_n, unimp_mask;
>  	int i, pmc;
>  
>  	__GUEST_ASSERT(expected_pmcr_n <= ARMV8_PMU_MAX_GENERAL_COUNTERS,
> @@ -324,15 +384,32 @@ static void guest_code(uint64_t expected_pmcr_n)
>  			"Expected PMCR.N: 0x%lx, PMCR.N: 0x%lx",
>  			pmcr_n, expected_pmcr_n);
>  
> +	/*
> +	 * Make sure that (RAZ) bits corresponding to unimplemented event
> +	 * counters in {PMCNTEN,PMOVS}{SET,CLR}_EL1 registers are reset to zero.
> +	 * (NOTE: bits for implemented event counters are reset to UNKNOWN)
> +	 */
> +	unimp_mask = GENMASK_ULL(ARMV8_PMU_MAX_GENERAL_COUNTERS - 1, pmcr_n);
> +	check_bitmap_pmu_regs(unimp_mask, false);
wrt above comment, this also checks pmintenset|clr_el1.
> +
>  	/*
>  	 * Tests for reading/writing PMU registers for implemented counters.
> -	 * Use each combination of PMEVT{CNTR,TYPER}<n>_EL0 accessor functions.
> +	 * Use each combination of PMEV{CNTR,TYPER}<n>_EL0 accessor functions.
>  	 */
>  	for (i = 0; i < ARRAY_SIZE(pmc_accessors); i++) {
>  		for (pmc = 0; pmc < pmcr_n; pmc++)
>  			test_access_pmc_regs(&pmc_accessors[i], pmc);
>  	}
>  
> +	/*
> +	 * Tests for reading/writing PMU registers for unimplemented counters.
> +	 * Use each combination of PMEV{CNTR,TYPER}<n>_EL0 accessor functions.
> +	 */
> +	for (i = 0; i < ARRAY_SIZE(pmc_accessors); i++) {
> +		for (pmc = pmcr_n; pmc < ARMV8_PMU_MAX_GENERAL_COUNTERS; pmc++)
> +			test_access_invalid_pmc_regs(&pmc_accessors[i], pmc);
> +	}
> +
>  	GUEST_DONE();
>  }
>  
> diff --git a/tools/testing/selftests/kvm/include/aarch64/processor.h b/tools/testing/selftests/kvm/include/aarch64/processor.h
> index cb537253a6b9..c42d683102c7 100644
> --- a/tools/testing/selftests/kvm/include/aarch64/processor.h
> +++ b/tools/testing/selftests/kvm/include/aarch64/processor.h
> @@ -104,6 +104,7 @@ enum {
>  #define ESR_EC_SHIFT		26
>  #define ESR_EC_MASK		(ESR_EC_NUM - 1)
>  
> +#define ESR_EC_UNKNOWN		0x0
>  #define ESR_EC_SVC64		0x15
>  #define ESR_EC_IABT		0x21
>  #define ESR_EC_DABT		0x25

Thanks

Eric