[PATCH] drm/xe/guc: Improve robustness of GuC log dumping to dmesg
John Harrison
john.c.harrison at intel.com
Tue Apr 30 23:56:49 UTC 2024
On 4/30/2024 16:44, Matthew Brost wrote:
> On Tue, Apr 30, 2024 at 04:34:36PM -0700, John.C.Harrison at Intel.com wrote:
>> From: John Harrison <John.C.Harrison at Intel.com>
>>
>> There is a debug mechanism for dumping the GuC log as an ASCII hex
>> stream via dmesg. This is extremely useful for situations where it is
>> not possibe to query the log from debugfs (self tests, bugs that cause
>> the driver to fail to load, system hangs, etc.). However, dumping via
>> dmesg is not the most reliable. The dmesg buffer is limited in size,
>> can be rate limited and a simple hex stream is hard to parse by tools.
>>
>> So add extra information to the dump to make it more robust and
>> parsable. This includes adding start and end tags to delimit the dump,
>> using longer lines to reduce the per line overhead, adding a rolling
>> count to check for missing lines and interleaved concurrent dumps and
>> adding other important information such as the GuC version number and
>> timestamp offset.
>>
>> Signed-off-by: John Harrison <John.C.Harrison at Intel.com>
>> ---
>> drivers/gpu/drm/xe/regs/xe_guc_regs.h | 1 +
>> drivers/gpu/drm/xe/xe_guc_log.c | 78 ++++++++++++++++++++++-----
>> 2 files changed, 66 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/xe/regs/xe_guc_regs.h b/drivers/gpu/drm/xe/regs/xe_guc_regs.h
>> index 11682e675e0f..45fb3707fabe 100644
>> --- a/drivers/gpu/drm/xe/regs/xe_guc_regs.h
>> +++ b/drivers/gpu/drm/xe/regs/xe_guc_regs.h
>> @@ -82,6 +82,7 @@
>> #define HUC_LOADING_AGENT_GUC REG_BIT(1)
>> #define GUC_WOPCM_OFFSET_VALID REG_BIT(0)
>> #define GUC_MAX_IDLE_COUNT XE_REG(0xc3e4)
>> +#define GUC_PMTIMESTAMP XE_REG(0xc3e8)
>>
>> #define GUC_SEND_INTERRUPT XE_REG(0xc4c8)
>> #define GUC_SEND_TRIGGER REG_BIT(0)
>> diff --git a/drivers/gpu/drm/xe/xe_guc_log.c b/drivers/gpu/drm/xe/xe_guc_log.c
>> index a37ee3419428..ea269efd9c21 100644
>> --- a/drivers/gpu/drm/xe/xe_guc_log.c
>> +++ b/drivers/gpu/drm/xe/xe_guc_log.c
>> @@ -7,10 +7,19 @@
>>
>> #include <drm/drm_managed.h>
>>
>> +#include "regs/xe_guc_regs.h"
>> #include "xe_bo.h"
>> #include "xe_gt.h"
>> #include "xe_map.h"
>> +#include "xe_mmio.h"
>> #include "xe_module.h"
>> +#include "xe_pm.h"
>> +
>> +static struct xe_guc *
>> +log_to_guc(struct xe_guc_log *log)
>> +{
>> + return container_of(log, struct xe_guc, log);
>> +}
>>
>> static struct xe_gt *
>> log_to_gt(struct xe_guc_log *log)
>> @@ -49,32 +58,75 @@ static size_t guc_log_size(void)
>> CAPTURE_BUFFER_SIZE;
>> }
>>
>> +#define BYTES_PER_WORD sizeof(u32)
>> +#define WORDS_PER_DUMP 8
>> +#define DUMPS_PER_LINE 4
>> +#define LINES_PER_READ 4
>> +#define WORDS_PER_READ (WORDS_PER_DUMP * DUMPS_PER_LINE * LINES_PER_READ)
>> +
>> void xe_guc_log_print(struct xe_guc_log *log, struct drm_printer *p)
>> {
>> + static int g_count;
>> + struct xe_uc_fw_version *ver = &log_to_guc(log)->fw.versions.found[XE_UC_FW_VER_RELEASE];
>> struct xe_device *xe = log_to_xe(log);
>> size_t size;
>> - int i, j;
>> + char line_buff[DUMPS_PER_LINE * WORDS_PER_DUMP * 9 + 1];
>> + int l_count = g_count++;
>> + int line = 0;
>> + int i, j, k;
>> + u64 ktime;
>> + u32 stamp;
>>
>> xe_assert(xe, log->bo);
>>
>> size = log->bo->size;
>>
>> -#define DW_PER_READ 128
>> - xe_assert(xe, !(size % (DW_PER_READ * sizeof(u32))));
>> - for (i = 0; i < size / sizeof(u32); i += DW_PER_READ) {
>> - u32 read[DW_PER_READ];
>> + drm_printf(p, "[Capture/%d.%d] Dumping GuC log for %ps...\n",
>> + l_count, line++, __builtin_return_address(0));
>> +
>> + drm_printf(p, "[Capture/%d.%d] GuC version %u.%u.%u\n",
>> + l_count, line++, ver->major, ver->minor, ver->patch);
>> +
>> + ktime = ktime_get_boottime_ns();
>> + drm_printf(p, "[Capture/%d.%d] Kernel timestamp: 0x%08llX [%llu]\n",
>> + l_count, line++, ktime, ktime);
>>
>> - xe_map_memcpy_from(xe, read, &log->bo->vmap, i * sizeof(u32),
>> - DW_PER_READ * sizeof(u32));
>> -#define DW_PER_PRINT 4
>> - for (j = 0; j < DW_PER_READ / DW_PER_PRINT; ++j) {
>> - u32 *print = read + j * DW_PER_PRINT;
>> + xe_pm_runtime_get(xe);
>> + stamp = xe_mmio_read32(log_to_gt(log), GUC_PMTIMESTAMP);
>> + xe_pm_runtime_put(xe);
> Just a quick drive by comment, fine grained PM control like this frowned
> upon in Xe or maybe even not allowed. Rodrigo / Matt Auld would would be
> the experts here.
>
> Presumbly all the callers should already have a PM ref.
It wasn't clear that this would be the case.
And the whole pm_runtime interface is exceedingly confusing. _get calls
get_noresume then does a task ownership test and calls resume,
_resume_and_get does exactly the same but in a different order, plus
there is _get_if_active and _get_if_in_use. Plus _get_ioctl which is for
calling *before* making an IOCTL (where an IOCTL is a call from the user
into the kernel!). And none of these have any documentation beyond a
single sentence that is simply re-writing the function name with with
prepositions added.
So I am unsurprised if this is not the correct way to do it but I have
no idea what would be the correct method.
>
>> + drm_printf(p, "[Capture/%d.%d] GuC timestamp: 0x%08X [%u]\n",
>> + l_count, line++, stamp, stamp);
>>
>> - drm_printf(p, "0x%08x 0x%08x 0x%08x 0x%08x\n",
>> - *(print + 0), *(print + 1),
>> - *(print + 2), *(print + 3));
>> + drm_printf(p, "[Capture/%d.%d] CS timestamp frequency: %u Hz\n",
>> + l_count, line++, log_to_gt(log)->info.reference_clock);
>> +
>> + xe_assert(xe, !(size % (WORDS_PER_READ * BYTES_PER_WORD)));
>> + for (i = 0; i < size / BYTES_PER_WORD; i += WORDS_PER_READ) {
>> + u32 read[WORDS_PER_READ];
>> +
>> + xe_map_memcpy_from(xe, read, &log->bo->vmap, i * BYTES_PER_WORD,
>> + WORDS_PER_READ * BYTES_PER_WORD);
>> +
> Also I think the above pukes without a PM ref too.
If that is the case, should there not have been an assert about having a
PM reference at the start of the function?
Although I don't see why a PM reference would be required to read from
system memory on an integrated part? Maybe for a discrete part. But I
would assume that having a vmap in existence would mean the memory is
locked and accessible. Either that, or a vmap is only allowed to be used
by accessor functions which themselves do whatever is required to make
the access work.
John.
>
> Matt
>
>> + for (j = 0; j < WORDS_PER_READ; ) {
>> + u32 done = 0;
>> +
>> + for (k = 0; k < DUMPS_PER_LINE; k++) {
>> + line_buff[done++] = ' ';
>> + done += hex_dump_to_buffer(read + j,
>> + sizeof(*read) * (WORDS_PER_READ - j),
>> + WORDS_PER_DUMP * BYTES_PER_WORD,
>> + BYTES_PER_WORD,
>> + line_buff + done,
>> + sizeof(line_buff) - done,
>> + false);
>> + j += WORDS_PER_DUMP;
>> + }
>> +
>> + drm_printf(p, "[Capture/%d.%d]%s\n", l_count, line++, line_buff);
>> }
>> }
>> +
>> + drm_printf(p, "[Capture/%d.%d] Done.\n", l_count, line++);
>> }
>>
>> int xe_guc_log_init(struct xe_guc_log *log)
>> --
>> 2.43.2
>>
More information about the Intel-xe
mailing list