Re: [kvm-unit-tests PATCH v4 5/5] riscv: sbi: Add test for timer extension

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On Sun, Jul 21, 2024 at 03:06:00PM GMT, James Raphael Tiovalen wrote:
> Add a test for the set_timer function of the time extension. The test
> checks that:
> - The time extension is available
> - The installed timer interrupt handler is called
> - The timer interrupt is received within a reasonable time interval
> - The timer interrupt pending bit is cleared after the set_timer SBI
>   call is made
> - The timer interrupt can be cleared either by requesting a timer
>   interrupt infinitely far into the future or by masking the timer
>   interrupt
> 
> The timer interrupt delay can be set using the TIMER_DELAY environment
> variable in microseconds. The default delay value is 200 milliseconds.
> Since the interrupt can arrive a little later than the specified delay,
> allow some margin of error. This margin of error can be specified via
> the TIMER_MARGIN environment variable in microseconds. The default
> margin of error is 200 milliseconds.
> 
> Signed-off-by: James Raphael Tiovalen <jamestiotio@xxxxxxxxx>
> ---
>  lib/riscv/asm/csr.h   |   8 +++
>  lib/riscv/asm/sbi.h   |   5 ++
>  lib/riscv/asm/timer.h |  10 ++++
>  riscv/sbi.c           | 132 ++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 155 insertions(+)
> 
> diff --git a/lib/riscv/asm/csr.h b/lib/riscv/asm/csr.h
> index a9b1bd42..24b333e0 100644
> --- a/lib/riscv/asm/csr.h
> +++ b/lib/riscv/asm/csr.h
> @@ -4,11 +4,15 @@
>  #include <linux/const.h>
>  
>  #define CSR_SSTATUS		0x100
> +#define CSR_SIE			0x104
>  #define CSR_STVEC		0x105
>  #define CSR_SSCRATCH		0x140
>  #define CSR_SEPC		0x141
>  #define CSR_SCAUSE		0x142
>  #define CSR_STVAL		0x143
> +#define CSR_SIP			0x144
> +#define CSR_STIMECMP		0x14d
> +#define CSR_STIMECMPH		0x15d
>  #define CSR_SATP		0x180
>  #define CSR_TIME		0xc01
>  
> @@ -47,6 +51,10 @@
>  #define IRQ_S_GEXT		12
>  #define IRQ_PMU_OVF		13
>  
> +#define IE_TIE			(_AC(0x1, UL) << IRQ_S_TIMER)
> +
> +#define IP_TIP			IE_TIE
> +
>  #ifndef __ASSEMBLY__
>  
>  #define csr_swap(csr, val)					\
> diff --git a/lib/riscv/asm/sbi.h b/lib/riscv/asm/sbi.h
> index 5e1a674a..73ab5438 100644
> --- a/lib/riscv/asm/sbi.h
> +++ b/lib/riscv/asm/sbi.h
> @@ -16,6 +16,7 @@
>  
>  enum sbi_ext_id {
>  	SBI_EXT_BASE = 0x10,
> +	SBI_EXT_TIME = 0x54494d45,
>  	SBI_EXT_HSM = 0x48534d,
>  	SBI_EXT_SRST = 0x53525354,
>  };
> @@ -37,6 +38,10 @@ enum sbi_ext_hsm_fid {
>  	SBI_EXT_HSM_HART_SUSPEND,
>  };
>  
> +enum sbi_ext_time_fid {
> +	SBI_EXT_TIME_SET_TIMER = 0,
> +};
> +
>  struct sbiret {
>  	long error;
>  	long value;
> diff --git a/lib/riscv/asm/timer.h b/lib/riscv/asm/timer.h
> index f7504f84..b3514d3f 100644
> --- a/lib/riscv/asm/timer.h
> +++ b/lib/riscv/asm/timer.h
> @@ -11,4 +11,14 @@ static inline uint64_t timer_get_cycles(void)
>  	return csr_read(CSR_TIME);
>  }
>  
> +static inline void timer_irq_enable(void)
> +{
> +	csr_set(CSR_SIE, IE_TIE);
> +}
> +
> +static inline void timer_irq_disable(void)
> +{
> +	csr_clear(CSR_SIE, IE_TIE);
> +}
> +
>  #endif /* _ASMRISCV_TIMER_H_ */
> diff --git a/riscv/sbi.c b/riscv/sbi.c
> index 762e9711..fe2fe771 100644
> --- a/riscv/sbi.c
> +++ b/riscv/sbi.c
> @@ -6,7 +6,21 @@
>   */
>  #include <libcflat.h>
>  #include <stdlib.h>
> +#include <limits.h>
> +#include <asm/barrier.h>
> +#include <asm/csr.h>
> +#include <asm/delay.h>
> +#include <asm/isa.h>
> +#include <asm/processor.h>
>  #include <asm/sbi.h>
> +#include <asm/smp.h>
> +#include <asm/timer.h>
> +
> +static bool timer_works;
> +static bool mask_timer_irq;
> +static bool timer_irq_set;
> +static bool timer_irq_cleared;
> +static unsigned long timer_irq_count;
>  
>  static void help(void)
>  {
> @@ -19,6 +33,34 @@ static struct sbiret __base_sbi_ecall(int fid, unsigned long arg0)
>  	return sbi_ecall(SBI_EXT_BASE, fid, arg0, 0, 0, 0, 0, 0);
>  }
>  
> +static struct sbiret __time_sbi_ecall(unsigned long stime_value)
> +{
> +	return sbi_ecall(SBI_EXT_TIME, SBI_EXT_TIME_SET_TIMER, stime_value, 0, 0, 0, 0, 0);
> +}
> +
> +static inline bool timer_irq_pending(void)

'inline' isn't useful in a source file. The compiler will do what it wants
anyway.

> +{
> +	return csr_read(CSR_SIP) & IP_TIP;
> +}
> +
> +static void timer_irq_handler(struct pt_regs *regs)
> +{
> +	if (timer_irq_count < ULONG_MAX)
> +		++timer_irq_count;
> +
> +	timer_works = true;
> +	if (timer_irq_pending())
> +		timer_irq_set = true;
> +
> +	if (mask_timer_irq) {
> +		timer_irq_disable();
> +	} else {
> +		__time_sbi_ecall(ULONG_MAX);
> +		if (!timer_irq_pending())
> +			timer_irq_cleared = true;
> +	}
> +}
> +
>  static bool env_or_skip(const char *env)
>  {
>  	if (!getenv(env)) {
> @@ -112,6 +154,95 @@ static void check_base(void)
>  	report_prefix_pop();
>  }
>  
> +static void check_time(void)
> +{
> +	struct sbiret ret;
> +	unsigned long begin, end, duration;
> +	unsigned long d = getenv("TIMER_DELAY") ? strtol(getenv("TIMER_DELAY"), NULL, 0)
> +						: 200000;
> +	unsigned long margin = getenv("TIMER_MARGIN") ? strtol(getenv("TIMER_MARGIN"), NULL, 0)
> +						      : 200000;
> +
> +	d = usec_to_cycles(d);
> +	margin = usec_to_cycles(margin);
> +
> +	report_prefix_push("time");
> +
> +	if (!sbi_probe(SBI_EXT_TIME)) {
> +		report_skip("time extension not available");
> +		report_prefix_pop();
> +		return;
> +	}
> +
> +	report_prefix_push("set_timer");
> +
> +	install_irq_handler(IRQ_S_TIMER, timer_irq_handler);
> +	local_irq_enable();
> +	if (cpu_has_extension(smp_processor_id(), ISA_SSTC)) {
> +		csr_write(CSR_STIMECMP, ULONG_MAX);
> +#if __riscv_xlen == 32
> +		csr_write(CSR_STIMECMPH, ULONG_MAX);
> +#endif
> +	}
> +	timer_irq_enable();
> +
> +	begin = timer_get_cycles();
> +	ret = __time_sbi_ecall(begin + d);
> +
> +	report(!ret.error, "set timer");
> +	if (ret.error)
> +		report_info("set timer failed with %ld\n", ret.error);
> +
> +	report(!timer_irq_pending(), "pending timer interrupt bit cleared");
> +
> +	while ((end = timer_get_cycles()) <= (begin + d + margin) && !timer_works)
> +		cpu_relax();
> +
> +	report(timer_works, "timer interrupt received");
> +	report(timer_irq_set, "pending timer interrupt bit set in irq handler");
> +	report(timer_irq_cleared, "pending timer interrupt bit cleared by setting timer to -1");

timer_irq_cleared being true is only interesting if timer_irq_set is also
true. This test should be 'timer_irq_set && timer_irq_cleared'

> +
> +	if (timer_works) {
> +		duration = end - begin;
> +		report(duration >= d && duration <= (d + margin), "timer delay honored");
> +	}
> +
> +	if (timer_irq_count > 1)
> +		report_fail("timer interrupt received multiple times");
> +
> +	timer_works = false;
> +	timer_irq_set = false;
> +	timer_irq_count = 0;
> +	mask_timer_irq = true;

nit: We could collect all these variables into one struct, i.e.

 struct timer_info {
  bool timer_works;
  bool mask_timer_irq;
  bool timer_irq_set;
  bool timer_irq_cleared;
  unsigned long timer_irq_count;
 };

Then it's easy to reset them to zero with something like

  timer_info = (struct timer_info){ .mask_timer_irq = true, };

> +	begin = timer_get_cycles();
> +	ret = __time_sbi_ecall(begin + d);
> +
> +	report(!ret.error, "set timer for mask irq test");
> +	if (ret.error)
> +		report_info("set timer for mask irq test failed with %ld\n", ret.error);
> +
> +	while ((end = timer_get_cycles()) <= (begin + d + margin) && !timer_works)
> +		cpu_relax();
> +
> +	report(timer_works, "timer interrupt received for mask irq test");
> +	report(timer_irq_set, "pending timer interrupt bit set in irq handler for mask irq test");
> +
> +	if (timer_works) {
> +		duration = end - begin;
> +		report(duration >= d && duration <= (d + margin),
> +		       "timer delay honored for mask irq test");
> +	}
> +
> +	if (timer_irq_count > 1)
> +		report_fail("timer interrupt received multiple times for mask irq test");
> +
> +	local_irq_disable();
> +	install_irq_handler(IRQ_S_TIMER, NULL);
> +
> +	report_prefix_pop();
> +	report_prefix_pop();
> +}
> +
>  int main(int argc, char **argv)
>  {
>  
> @@ -122,6 +253,7 @@ int main(int argc, char **argv)
>  
>  	report_prefix_push("sbi");
>  	check_base();
> +	check_time();
>  
>  	return report_summary();
>  }
> -- 
> 2.43.0
>

Thanks,
drew




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