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From: Mika Kuoppala <mika.kuoppala@linux.intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>, intel-gfx@lists.freedesktop.org
Cc: Mika@freedesktop.org
Subject: Re: [PATCH 3/3] drm/i915/execlists: Relax CSB force-mmio for VT-d
Date: Mon, 14 May 2018 11:33:23 +0300	[thread overview]
Message-ID: <874ljaab70.fsf@gaia.fi.intel.com> (raw)
In-Reply-To: <152605343642.14639.4999095151169602692@mail.alporthouse.com>

Chris Wilson <chris@chris-wilson.co.uk> writes:

> Quoting Chris Wilson (2018-05-11 13:11:47)
>> The original switch to use CSB from the HWSP was plagued by the effort
>> of read ordering on VT-d; we would read the WRITE pointer from the HWSP
>> before it had completed writing the CSB contents. The mystery comes down
>> to the lack of rmb() for correct ordering with respect to the writes
>> from HW, and with that resolved we can remove the VT-d special casing.
>
> Mika's been able to reproduce the VT-d issue and is soak testing this
> fix, so I'll leave that until he's had a chance to confirm it survives.
> In the meantime, I think we are reasonably happy this is the right fix
> for Cannonlake and beyond, so I've pushed the first two patches.
>

My kbl was quite sensitive to this, sometimes failing to even
boot without the vtd backoff.

Now after weekend of gem_ctx_switch and gem_exec_whisper
I am confident for,

Tested-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
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  reply	other threads:[~2018-05-14  8:33 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-11 12:11 [PATCH 1/3] drm/i915/execlists: Use rmb() to order CSB reads Chris Wilson
2018-05-11 12:11 ` [PATCH 2/3] Revert "drm/i915/cnl: Use mmio access to context status buffer" Chris Wilson
2018-05-11 12:11 ` [PATCH 3/3] drm/i915/execlists: Relax CSB force-mmio for VT-d Chris Wilson
2018-05-11 12:14   ` Chris Wilson
2018-05-11 15:43   ` Chris Wilson
2018-05-14  8:33     ` Mika Kuoppala [this message]
2018-05-14  8:43       ` Chris Wilson
2018-05-11 12:42 ` ✗ Fi.CI.CHECKPATCH: warning for series starting with [1/3] drm/i915/execlists: Use rmb() to order CSB reads Patchwork
2018-05-11 13:02 ` ✓ Fi.CI.BAT: success " Patchwork
2018-05-11 13:52 ` ✓ Fi.CI.IGT: " Patchwork

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