Re: [kvm-unit-tests PATCH v5 5/5] riscv: sbi: Add test for timer extension

Andrew Jones
2024-07-29T13:31:06Z

On Mon, Jul 29, 2024 at 12:50:22AM 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@gmail.com>
> ---
> lib/riscv/asm/csr.h | 8 +++
> lib/riscv/asm/sbi.h | 5 ++
> lib/riscv/asm/timer.h | 10 +++
> riscv/sbi.c | 144 ++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 167 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..044258bb 100644
> --- a/riscv/sbi.c
> +++ b/riscv/sbi.c
> @@ -6,7 +6,25 @@
> */
> #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>
> +
> +struct timer_info {
> + bool timer_works;
> + bool mask_timer_irq;
> + bool timer_irq_set;
> + bool timer_irq_cleared;
> + unsigned long timer_irq_count;
> +};
> +
> +static struct timer_info timer_info_;

I'd rather call this just 'timer_info' than 'timer_info_'. I usually
prefer to use a different name than the struct for grepping purposes,
but for a static structure of a small file it doesn't really matter.

>
> static void help(void)
> {
> @@ -19,6 +37,36 @@ 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 bool timer_irq_pending(void)
> +{
> + return csr_read(CSR_SIP) & IP_TIP;
> +}
> +
> +static void timer_irq_handler(struct pt_regs *regs)
> +{
> + if (timer_info_.timer_irq_count < ULONG_MAX)
> + ++timer_info_.timer_irq_count;
> +
> + timer_info_.timer_works = true;
> + if (timer_irq_pending())
> + timer_info_.timer_irq_set = true;
> +
> + if (timer_info_.mask_timer_irq) {
> + timer_irq_disable();
> + __time_sbi_ecall(0);
> + } else {
> + __time_sbi_ecall(ULONG_MAX);
> + }
> +
> + if (!timer_irq_pending())
> + timer_info_.timer_irq_cleared = true;
> +}
> +
> static bool env_or_skip(const char *env)
> {
> if (!getenv(env)) {
> @@ -112,6 +160,101 @@ 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_info_.timer_works)
> + cpu_relax();
> +
> + report(timer_info_.timer_works, "timer interrupt received");
> + report(timer_info_.timer_irq_set, "pending timer interrupt bit set in irq handler");
> + report(timer_info_.timer_irq_set && timer_info_.timer_irq_cleared,
> + "pending timer interrupt bit cleared by setting timer to -1");
> +
> + if (timer_info_.timer_works) {
> + duration = end - begin;
> + report(duration >= d && duration <= (d + margin), "timer delay honored");
> + }
> +
> + if (timer_info_.timer_irq_count > 1)
> + report_fail("timer interrupt received multiple times");
> +
> + if (csr_read(CSR_SIE) & IE_TIE) {
> + 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_info_.timer_works)
> + cpu_relax();
> +
> + report(timer_info_.timer_works, "timer interrupt received for mask irq test");
> + report(timer_info_.timer_irq_set,
> + "pending timer interrupt bit set in irq handler for mask irq test");
> + report(timer_info_.timer_irq_set && timer_info_.timer_irq_cleared,
> + "pending timer interrupt bit cleared by masking timer irq");
> +
> + if (timer_info_.timer_works) {
> + duration = end - begin;
> + report(duration >= d && duration <= (d + margin),
> + "timer delay honored for mask irq test");
> + }
> +
> + if (timer_info_.timer_irq_count > 1)
> + report_fail("timer interrupt received multiple times for mask irq test");

nit: we could share all the code in the body of this if-statement with the
code above if we just create a function which takes a const char * which
would be NULL for the first invocation and "for mask irq test" for the
second.

> + } else {
> + report_skip("timer irq enable bit is not writable, skipping 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 +265,7 @@ int main(int argc, char **argv)
>
> report_prefix_push("sbi");
> check_base();
> + check_time();
>
> return report_summary();
> }
> --
> 2.43.0
>

Reviewed-by: Andrew Jones <andrew.jones@linux.dev>

Thanks,
drew