Re: [PATCH 2/2] drm/i915: Enable render context support for gen4 (Broadwater to Cantiga)

[Kenneth Graunke <kenneth@whitecape.org>]

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On Tuesday, January 8, 2019 5:02:59 PM PST Chris Wilson wrote:
> Quoting Chris Wilson (2019-01-08 12:28:18)
> > Broadwater and the rest of gen4  do support being able to saving and
> > reloading context specific registers between contexts, providing isolation
> > of the basic GPU state (as programmable by userspace). This allows
> > userspace to assume that the GPU retains their state from one batch to the
> > next, minimising the amount of state it needs to reload and manually save
> > across batches.
> 
> Well Crestline's render context contains a nasty booby trap.
> 
> [  152.065764] hangcheck rcs0
> [  152.065770] hangcheck 	current seqno 1b89, last 1bc5, hangcheck 1b89 [5984 ms]
> [  152.065773] hangcheck 	Reset count: 0 (global 0)
> [  152.065774] hangcheck 	Requests:
> [  152.065779] hangcheck 		first  1b8a* [5:1b8a] @ 7376ms: rcs0
> [  152.065783] hangcheck 		last   1bc5+ [5:1bc5] @ 7328ms: rcs0
> [  152.065786] hangcheck 		active 1b8a* [5:1b8a] @ 7376ms: rcs0
> [  152.065789] hangcheck 		ring->start:  0x00004000
> [  152.065792] hangcheck 		ring->head:   0x00017dd0
> [  152.065794] hangcheck 		ring->tail:   0x00019fb0
> [  152.065795] hangcheck 		ring->emit:   0x00019fb0
> [  152.065797] hangcheck 		ring->space:  0x000050a0
> [  152.065801] hangcheck [head 17df0, postfix 17e60, tail 17e80, batch 0x00000000_00335000]:
> [  152.065809] hangcheck [0000] 02000002 7a004002 1fffe004 00000000 00000000 02000000 02000000 02000000
> [  152.065813] hangcheck [0020] 02000000 02000000 02000000 02000000 02000000 02000000 02000000 02000000
> [  152.065817] hangcheck [0040] 02000000 7a004002 1fffe004 00000000 00000000 02000002 00000000 0c000000
> [  152.065821] hangcheck [0060] 0032f10c 00000000 18800180 00335000 02000000 10800001 00000100 00001b8a
> [  152.065825] hangcheck [0080] 10800001 000000c0 00001b8a 01000000
> [  152.065829] hangcheck 	CCID: 0x0003210d
> [  152.065831] hangcheck 	RING_START: 0x00004000
> [  152.065834] hangcheck 	RING_HEAD:  0x00017e54
> [  152.065836] hangcheck 	RING_TAIL:  0x00019fb0
> [  152.065839] hangcheck 	RING_CTL:   0x0001f001
> [  152.065841] hangcheck 	RING_MODE:  0x00000040
> [  152.065844] hangcheck 	ACTHD:  0x00000000_00e17e54
> [  152.065847] hangcheck 	BBADDR: 0x00000000_002f81e0
> [  152.065849] hangcheck 	DMA_FADDR: 0x00000000_0001be50
> [  152.065851] hangcheck 	IPEIR: 0x00000000
> [  152.065853] hangcheck 	IPEHR: 0x60020100 # CONSTANT_BUFFER see 0x1d4
> [  152.065860] hangcheck 		E 1b8a* [5:1b8a] @ 7376ms: rcs0
> [  152.065864] hangcheck 		E 1b8b+ [5:1b8b] @ 7376ms: rcs0
> [  152.065867] hangcheck 		E 1b8c [5:1b8c] @ 7376ms: rcs0
> [  152.065870] hangcheck 		E 1b8d [5:1b8d] @ 7376ms: rcs0
> [  152.065873] hangcheck 		E 1b8e [5:1b8e] @ 7376ms: rcs0
> [  152.065877] hangcheck 		E 1b8f [5:1b8f] @ 7376ms: rcs0
> [  152.065880] hangcheck 		E 1b90 [5:1b90] @ 7372ms: rcs0
> [  152.065888] hangcheck 		...skipping 52 executing requests...
> [  152.065891] hangcheck 		E 1bc5+ [5:1bc5] @ 7328ms: rcs0
> [  152.065893] hangcheck 		Queue priority: -2147483648
> [  152.065909] hangcheck HWSP:
> [  152.065913] hangcheck [0000] 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [  152.065915] hangcheck *
> [  152.065919] hangcheck [00c0] 00001b89 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [  152.065923] hangcheck [00e0] 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [  152.065927] hangcheck [0100] 00001b89 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [  152.065931] hangcheck [0120] 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [  152.065933] hangcheck *
> [  152.065945] hangcheck Context:
> [  152.065960] hangcheck [0000] 00000000 1100002b 00002120 ffff6800 00002124 ffff0180 000020e4 ffff0044
> [  152.065966] hangcheck [0020] 000020c0 ffff0000 00002310 00000010 00002314 00000000 00002318 00000008
> [  152.065970] hangcheck [0040] 0000231c 00000000 00002320 00000000 00002324 00000000 00002328 00000000
> [  152.065975] hangcheck [0060] 0000232c 00000000 00002330 00000000 00002334 00000000 00002338 00000000
> [  152.065980] hangcheck [0080] 0000233c 00000000 00002340 00000000 00002344 00000000 00002348 00000000
> [  152.065985] hangcheck [00a0] 0000234c 00000000 00002350 00000000 00002354 00000000 00000000 00000000
> [  152.065990] hangcheck [00c0] 61040000 60010000 00000014 60003f01 0320a020 10000042 60020000 00000001
> [  152.065994] hangcheck [00e0] 61010004 00000001 00316001 00000001 00000001 00000001 61020000 00000000
> [  152.065999] hangcheck [0100] 79000002 00000000 00000000 00000000 79050003 2c08007f 00035000 00000000
> [  152.066004] hangcheck [0120] 00000000 79040002 00000000 f792ec01 0f9fa8a6 79040002 40000000 f7bdfd51
> [  152.066009] hangcheck [0140] 2fdfb8e7 79040002 80000000 7392fc15 efdfacb6 79040002 c0000000 b5d2ec43
> [  152.066014] hangcheck [0160] 4fffabae 79010003 00000000 00000000 00000000 00000000 79090000 1ac4814a
> [  152.066019] hangcheck [0180] 79060000 00001603 79080001 8020d7bb 1eb70165 00000000 00000000 00000000
> [  152.066024] hangcheck [01a0] 78000005 00316160 00000000 00316181 00316140 003160c0 00316040 78010004
> [  152.066028] hangcheck [01c0] 00000000 00000000 00000000 00000000 00000080 60020100 0031e001 00000000
> [  152.066033] hangcheck [01e0] 40400006 00000000 00000000 00000000 00000000 00000000 00026000 00000000
> [  152.066038] hangcheck [0200] 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [  152.066043] hangcheck [0220] 780a0001 00000000 00000000 78080043 0000002c 0032e000 00000000 00000000
> [  152.066047] hangcheck [0240] 08000000 00000000 00000000 00000000 10000000 00000000 00000000 00000000
> [  152.066053] hangcheck [0260] 18000000 00000000 00000000 00000000 20000000 00000000 00000000 00000000
> [  152.066058] hangcheck [0280] 28000000 00000000 00000000 00000000 30000000 00000000 00000000 00000000
> [  152.066064] hangcheck [02a0] 38000000 00000000 00000000 00000000 40000000 00000000 00000000 00000000
> [  152.066069] hangcheck [02c0] 48000000 00000000 00000000 00000000 50000000 00000000 00000000 00000000
> [  152.066074] hangcheck [02e0] 58000000 00000000 00000000 00000000 60000000 00000000 00000000 00000000
> [  152.066079] hangcheck [0300] 68000000 00000000 00000000 00000000 70000000 00000000 00000000 00000000
> [  152.066084] hangcheck [0320] 78000000 00000000 00000000 00000000 80000000 00000000 00000000 00000000
> [  152.066089] hangcheck [0340] 78090023 04400000 11130000 00000000 00000000 00000000 00000000 00000000
> [  152.066094] hangcheck [0360] 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [  152.066099] hangcheck *
> [  152.066110] hangcheck [03c0] 00000000 00000000 00000000 00000000 00000000 780b0001 00000000 00000000
> [  152.066118] hangcheck [03e0] 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [  152.066123] hangcheck [0400] 7902000f ff90acdd ffa52f5d ff212a45 ff63edb4 ffa5aaed ffe9b9e5 ffd2ffcc
> [  152.066128] hangcheck [0420] ff65a3fc ff60a110 ff8928f4 ff51ae6d ffb052cd ff11c3f0 ff60bad6 ffc05bc9
> [  152.066133] hangcheck [0440] ffa87c10 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [  152.066138] hangcheck [0460] 7907001f 3c57ff12 30577d53 30136d15 3055fe5b 70577a56 3017dd16 3057fd12
> [  152.066142] hangcheck [0480] b15fd962 387379d4 2257fb10 3043fd30 a4773d50 3417de10 185b651c 3017f512
> [  152.066147] hangcheck [04a0] b819fd54 12576d8a 70c31900 a6666500 f870bd16 31769f3a bc7b5dc2 2497bb48
> [  152.066152] hangcheck [04c0] 30577d32 b0554d12 3c173d1a f0c73f90 7255fd93 307e7c92 381e5f88 24167552
> [  152.066156] hangcheck [04e0] 31532d1a 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [  152.066161] hangcheck [0500] 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [  152.066169] hangcheck *
> [  152.066455] hangcheck Idle? no
> [  152.066456] hangcheck Signals:
> [  152.066459] hangcheck 	[5:1b8b] @ 7376ms
> [  152.066462] hangcheck 	[5:1bc5] @ 7328ms
> 
> The issue, I think, in that is the CONSTANT_BUFFER command does an
> immediate load from the specified address,
> 
> Context:
> 	[01d4] 60020100 CONSTANT_BUFFER
> 	[01d8] 0031e001 address | length
> 
> and since this is a context image that address is not known to us and
> indeed may not any more be valid (the target buffer having been evicted).
> (But if it is a valid address but no longer populated, it should be
> reading scratch not hanging?)
> 
> The crazy thing is
> 
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/inte
> index 18fa319..e2aab92 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -1709,6 +1709,17 @@ static inline int mi_set_context(struct i915_request *rq,
>         int len;
>         u32 *cs;
> 
> +       cs = intel_ring_begin(rq, 4);
> +       if (IS_ERR(cs))
> +               return PTR_ERR(cs);
> +
> +       *cs++ = MI_STORE_DWORD_IMM_GEN4 | MI_USE_GGTT;
> +       *cs++ = 0;
> +       *cs++ = i915_ggtt_offset(rq->hw_context->state) + 0x1d4;
> +       *cs++ = 0x60020000; // replace active CONSTANT_BUFFER with inactive
> +
> +       intel_ring_advance(rq, cs);
> +
> 
> works.
> 
> Eh?
> -Chris

Does it work if you emit 3DSTATE_GLOBAL_DEPTH_OFFSET_CLAMP after
MI_SET_CONTEXT?  That was the source of most CONSTANT_BUFFER hangs
I saw on Broadwater/Crestline.  Notably, it's also a bug that was
fixed on Eaglelake/Cantiga...

https://gitlab.freedesktop.org/mesa/mesa/blob/master/src/mesa/drivers/dri/i965/brw_curbe.c#L317

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