On 15/05/2019 02:28, Suraj Jitindar Singh wrote:
> Currently the handler for a decrementer exception will simply reload the
> maximum value (0x7FFFFFFF), which will take ~4 seconds to expire again.
> This means that if a vcpu cedes, it will be ~4 seconds between wakeups.
>
> The h_cede_tm test is testing a known breakage when a guest cedes while
> suspended. To be sure we cede 500 times to check for the bug. However
> since it takes ~4 seconds to be woken up once we've ceded, we only get
> through ~20 iterations before we reach the 90 seconds timeout and the
> test appears to fail.
>
> Add an option when registering the decrementer handler to specify the
> value which should be reloaded by the handler, allowing the timeout to be
> chosen.
>
> Modify the spr test to use the max timeout to preserve existing
> behaviour.
> Modify the h_cede_tm test to use a 10ms timeout to ensure we can perform
> 500 iterations before hitting the 90 second time limit for a test.
>
> This means the h_cede_tm test now succeeds rather than timing out.
>
> Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@xxxxxxxxx>
>
> ---
>
> V1 -> V2:
> - Make decr variables static
> - Load intial decr value in tm test to ensure known value present
> ---
> lib/powerpc/handlers.c | 7 ++++---
> powerpc/sprs.c | 5 +++--
> powerpc/tm.c | 4 +++-
> 3 files changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/lib/powerpc/handlers.c b/lib/powerpc/handlers.c
> index be8226a..c8721e0 100644
> --- a/lib/powerpc/handlers.c
> +++ b/lib/powerpc/handlers.c
> @@ -12,11 +12,12 @@
>
> /*
> * Generic handler for decrementer exceptions (0x900)
> - * Just reset the decrementer back to its maximum value (0x7FFFFFFF)
> + * Just reset the decrementer back to the value specified when registering the
> + * handler
> */
> -void dec_except_handler(struct pt_regs *regs __unused, void *data __unused)
> +void dec_except_handler(struct pt_regs *regs __unused, void *data)
> {
> - uint32_t dec = 0x7FFFFFFF;
> + uint64_t dec = *((uint64_t *) data);
>
> asm volatile ("mtdec %0" : : "r" (dec));
> }
> diff --git a/powerpc/sprs.c b/powerpc/sprs.c
> index 6744bd8..0e2e1c9 100644
> --- a/powerpc/sprs.c
> +++ b/powerpc/sprs.c
> @@ -253,6 +253,7 @@ int main(int argc, char **argv)
> 0x1234567890ABCDEFULL, 0xFEDCBA0987654321ULL,
> -1ULL,
> };
> + static uint64_t decr = 0x7FFFFFFF; /* Max value */
>
> for (i = 1; i < argc; i++) {
> if (!strcmp(argv[i], "-w")) {
> @@ -288,8 +289,8 @@ int main(int argc, char **argv)
> (void) getchar();
> } else {
> puts("Sleeping...\n");
> - handle_exception(0x900, &dec_except_handler, NULL);
> - asm volatile ("mtdec %0" : : "r" (0x3FFFFFFF));
> + handle_exception(0x900, &dec_except_handler, &decr);
> + asm volatile ("mtdec %0" : : "r" (decr));
why do you replace the 0x3FFFFFFF by decr which is 0x7FFFFFFF?
> hcall(H_CEDE);
> }
>
> diff --git a/powerpc/tm.c b/powerpc/tm.c
> index bd56baa..c588985 100644
> --- a/powerpc/tm.c
> +++ b/powerpc/tm.c
> @@ -95,11 +95,13 @@ static bool enable_tm(void)
> static void test_h_cede_tm(int argc, char **argv)
> {
> int i;
> + static uint64_t decr = 0x3FFFFF; /* ~10ms */
>
> if (argc > 2)
> report_abort("Unsupported argument: '%s'", argv[2]);
>
> - handle_exception(0x900, &dec_except_handler, NULL);
> + handle_exception(0x900, &dec_except_handler, &decr);
> + asm volatile ("mtdec %0" : : "r" (decr));
>
> if (!start_all_cpus(halt, 0))
> report_abort("Failed to start secondary cpus");
>
Thanks,
Laurent
