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Today's Topics:
- Re: [RFC PATCH 00/97] Basic GuC submission support in the
i915 (Martin Peres) 2. [PATCH -next] drm/bridge: lt9611: Add missing MODULE_DEVICE_TABLE (Zou Wei) 3. Re: [Nouveau] [PATCH v2 2/2] drm/nouveau: Fix error return code in nouveau_backlight_init() (Pierre Moreau) 4. Re: [Nouveau] [PATCH v2 1/2] drm/nouveau: Fix ida leak (Pierre Moreau) 5. Re: [PATCH 1/3] virtio-gpu uapi: Add VIRTIO_GPU_F_EXPLICIT_FLUSH feature (Gerd Hoffmann) 6. Re: [Nouveau] [PATCH v2 1/2] drm/nouveau: Fix ida leak (Leizhen (ThunderTown))
Message: 1 Date: Wed, 12 May 2021 09:26:14 +0300 From: Martin Peres martin.peres@free.fr To: Matthew Brost matthew.brost@intel.com, "Bloomfield, Jon" jon.bloomfield@intel.com Cc: Daniel Vetter daniel@ffwll.ch, Jason Ekstrand jason@jlekstrand.net, intel-gfx intel-gfx@lists.freedesktop.org, dri-devel dri-devel@lists.freedesktop.org, "Ursulin, Tvrtko" tvrtko.ursulin@intel.com, "Ekstrand, Jason" jason.ekstrand@intel.com, "Ceraolo Spurio, Daniele" daniele.ceraolospurio@intel.com, "Vetter, Daniel" daniel.vetter@intel.com, "Harrison, John C" john.c.harrison@intel.com Subject: Re: [RFC PATCH 00/97] Basic GuC submission support in the i915 Message-ID: bb701cab-a68e-08ed-80e3-61be160bdc02@free.fr Content-Type: text/plain; charset=utf-8; format=flowed
On 11/05/2021 19:39, Matthew Brost wrote:
On Tue, May 11, 2021 at 08:26:59AM -0700, Bloomfield, Jon wrote:
-----Original Message----- From: Martin Peres martin.peres@free.fr Sent: Tuesday, May 11, 2021 1:06 AM To: Daniel Vetter daniel@ffwll.ch Cc: Jason Ekstrand jason@jlekstrand.net; Brost, Matthew matthew.brost@intel.com; intel-gfx intel-gfx@lists.freedesktop.org; dri-devel dri-devel@lists.freedesktop.org; Ursulin, Tvrtko tvrtko.ursulin@intel.com; Ekstrand, Jason jason.ekstrand@intel.com; Ceraolo Spurio, Daniele daniele.ceraolospurio@intel.com; Bloomfield, Jon jon.bloomfield@intel.com; Vetter, Daniel daniel.vetter@intel.com; Harrison, John C john.c.harrison@intel.com Subject: Re: [RFC PATCH 00/97] Basic GuC submission support in the i915
On 10/05/2021 19:33, Daniel Vetter wrote:
On Mon, May 10, 2021 at 3:55 PM Martin Peres martin.peres@free.fr
wrote:
On 10/05/2021 02:11, Jason Ekstrand wrote: > On May 9, 2021 12:12:36 Martin Peres martin.peres@free.fr wrote: > >> Hi, >> >> On 06/05/2021 22:13, Matthew Brost wrote: >>> Basic GuC submission support. This is the first bullet point in the >>> upstreaming plan covered in the following RFC [1]. >>> >>> At a very high level the GuC is a piece of firmware which sits between >>> the i915 and the GPU. It offloads some of the scheduling of contexts >>> from the i915 and programs the GPU to submit contexts. The i915 >>> communicates with the GuC and the GuC communicates with the
GPU.
>> >> May I ask what will GuC command submission do that execlist
won't/can't
>> do? And what would be the impact on users? Even forgetting the
troubled
>> history of GuC (instability, performance regression, poor level of user >> support, 6+ years of trying to upstream it...), adding this much code >> and doubling the amount of validation needed should come with a >> rationale making it feel worth it... and I am not seeing here. Would you >> mind providing the rationale behind this work? >> >>> >>> GuC submission will be disabled by default on all current upstream >>> platforms behind a module parameter - enable_guc. A value of 3 will >>> enable submission and HuC loading via the GuC. GuC submission
should
>>> work on all gen11+ platforms assuming the GuC firmware is present. >> >> What is the plan here when it comes to keeping support for execlist? I >> am afraid that landing GuC support in Linux is the first step towards >> killing the execlist, which would force users to use proprietary >> firmwares that even most Intel engineers have little influence over. >> Indeed, if "drm/i915/guc: Disable semaphores when using GuC
scheduling"
>> which states "Disable semaphores when using GuC scheduling as
semaphores
>> are broken in the current GuC firmware." is anything to go by, it means >> that even Intel developers seem to prefer working around the GuC >> firmware, rather than fixing it. > > Yes, landing GuC support may be the first step in removing execlist > support. The inevitable reality is that GPU scheduling is coming and > likely to be there only path in the not-too-distant future. (See also > the ongoing thread with AMD about fences.) I'm not going to pass > judgement on whether or not this is a good thing. I'm just reading the > winds and, in my view, this is where things are headed for good or ill. > > In answer to the question above, the answer to "what do we gain from > GuC?" may soon be, "you get to use your GPU." We're not there yet
and,
> again, I'm not necessarily advocating for it, but that is likely where > things are headed.
This will be a sad day, especially since it seems fundamentally opposed with any long-term support, on top of taking away user freedom to fix/tweak their system when Intel won't.
> A firmware-based submission model isn't a bad design IMO and, aside
from
> the firmware freedom issues, I think there are actual advantages to the > model. Immediately, it'll unlock a few features like parallel submission > (more on that in a bit) and long-running compute because they're > implemented in GuC and the work to implement them properly in the > execlist scheduler is highly non-trivial. Longer term, it may (no > guarantees) unlock some performance by getting the kernel out of the
way.
Oh, I definitely agree with firmware-based submission model not being a bad design. I was even cheering for it in 2015. Experience with it made me regret that deeply since :s
But with the DRM scheduler being responsible for most things, I fail to see what we could offload in the GuC except context switching (like every other manufacturer). The problem is, the GuC does way more than just switching registers in bulk, and if the number of revisions of the GuC is anything to go by, it is way too complex for me to feel comfortable with it.
We need to flesh out that part of the plan more, but we're not going to use drm scheduler for everything. It's only to handle the dma-fence legacy side of things, which means:
- timeout handling for batches that take too long
- dma_fence dependency sorting/handling
- boosting of context from display flips (currently missing, needs to
be ported from drm/i915)
The actual round-robin/preempt/priority handling is still left to the backend, in this case here the fw. So there's large chunks of code/functionality where drm/scheduler wont be involved in, and like Jason says: The hw direction winds definitely blow in the direction that this is all handled in hw.
The plan makes sense for a SRIOV-enable GPU, yes.
However, if the GuC is actually helping i915, then why not open source it and drop all the issues related to its stability? Wouldn't it be the perfect solution, as it would allow dropping execlist support for newer HW, and it would eliminate the concerns about maintenance of stable releases of Linux?
That the major version of the FW is high is not due to bugs - Bugs don't trigger major version bumps anyway.
Of course, where did I say they would?
Only interface changes increment the major version, and we do add features, to keep it relevant to the evolving hardware and OS landscape. When only Windows used GuC there was no reason not to minimize interface creep - GuC and KMD are released as an atomic bundle on Windows. With Linux, this is no longer the case, and has not been for some time.
AFAIK, Intel has been shipping GuC to customers since gen9, and upstream has been supporting command submission (albeit in a broken form) for years... until Michal finally disabled it after I asked for it to a bit over 2 years ago[1], when GuC was at major version 32.
So... not sure I would trust your word so blindly here.
[1] https://patchwork.freedesktop.org/patch/297997/?series=58760&rev=2#comme...
Jon hit the nail on head here - there hasn't been any reason not to bump the GuC version / change the interface until there is code upstream using the GuC. Once we push something that totally changes. Once SRIOV lands we literally can't the interface without breaking the world. Our goal is to this right before somethings lands, hence the high version number.
Good to hear! But Intel will continue to change the interface as new generations are made, so what is the support model for older GPUs / kernels which will be stuck on older major revisions?
Matt
We have been using GuC as the sole mechanism for submission on Windows since Gen8, and it has proven very reliable. This is in large part because it is simple, and designed from day 1 as a cohesive solution alongside the hardware.
Exactly, the GuC was designed with Windows' GPU model... which is not directly applicable to Linux. Also, Windows does not care as much about submission latency, whereas most Linux users still depend on glamor for 2D acceleration which is pretty much the biggest stress test for command submission latency. Also, features not used by the Windows driver or used in a different way are/will get broken (see the semaphore patch that works around it).
Will there be bugs in the future? Of course. It's a new i915 backend. There are bugs in the execlist backend too, and the runlist backend, and the majority of real-world software ever written. But the i915 GuC backend is way simpler than execlist, much easier to understand, and therefore much easier to maintain. It's a net win for i915 and Linux.
I am more than willing to accept the fact that the interface would be easier to work with, and I welcome anything that will simplify the driver... but not at the expense of regressing the user experience. One has to prove more than *just* code maintainability.
Feel free to iterate/land the code, but enabling guc-based command submission is waaaaayyyy too early, no matter how much you want it. This patch will remain a NACK from me until I see more of the plan to support *users* who are willing to use a proprietary firmware, performance analysis, what's the plan for users who will not want to use it, and what are the capabilities of GuC which could be used for privilege escalation and what is done to mitigate that.
Thanks, Martin
Jon
Message: 2 Date: Wed, 12 May 2021 14:45:55 +0800 From: Zou Wei zou_wei@huawei.com To: a.hajda@samsung.com, narmstrong@baylibre.com, robert.foss@linaro.org, Laurent.pinchart@ideasonboard.com, jonas@kwiboo.se, jernej.skrabec@siol.net, airlied@linux.ie, daniel@ffwll.ch Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Zou Wei zou_wei@huawei.com Subject: [PATCH -next] drm/bridge: lt9611: Add missing MODULE_DEVICE_TABLE Message-ID: 1620801955-19188-1-git-send-email-zou_wei@huawei.com Content-Type: text/plain
This patch adds missing MODULE_DEVICE_TABLE definition which generates correct modalias for automatic loading of this driver when it is built as an external module.
Reported-by: Hulk Robot hulkci@huawei.com Signed-off-by: Zou Wei zou_wei@huawei.com
drivers/gpu/drm/bridge/lontium-lt9611.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/drivers/gpu/drm/bridge/lontium-lt9611.c b/drivers/gpu/drm/bridge/lontium-lt9611.c index e8eb8de..29b1ce2 100644 --- a/drivers/gpu/drm/bridge/lontium-lt9611.c +++ b/drivers/gpu/drm/bridge/lontium-lt9611.c @@ -1215,6 +1215,7 @@ static struct i2c_device_id lt9611_id[] = { { "lontium,lt9611", 0 }, {} }; +MODULE_DEVICE_TABLE(i2c, lt9611_id);
static const struct of_device_id lt9611_match_table[] = { { .compatible = "lontium,lt9611" }, -- 2.6.2
Message: 3 Date: Wed, 12 May 2021 08:34:18 +0200 From: Pierre Moreau pierre.morrow@free.fr To: Zhen Lei thunder.leizhen@huawei.com Cc: Ben Skeggs bskeggs@redhat.com, David Airlie airlied@linux.ie, Daniel Vetter daniel@ffwll.ch, dri-devel dri-devel@lists.freedesktop.org, nouveau nouveau@lists.freedesktop.org Subject: Re: [Nouveau] [PATCH v2 2/2] drm/nouveau: Fix error return code in nouveau_backlight_init() Message-ID: 20210512063418.mgec2b5x73n6iwr6@Normandy.localdomain Content-Type: text/plain; charset=utf-8
Reviewed-by: Pierre Moreau pierre.morrow@free.fr
On 2021-05-11 ? 16:28, Zhen Lei wrote:
Fix to return a negative error code from the error handling case instead of 0, as done elsewhere in this function.
Fixes: db1a0ae21461 ("drm/nouveau/bl: Assign different names to interfaces") Suggested-by: Pierre Moreau pierre.morrow@free.fr Signed-off-by: Zhen Lei thunder.leizhen@huawei.com
drivers/gpu/drm/nouveau/nouveau_backlight.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/nouveau/nouveau_backlight.c b/drivers/gpu/drm/nouveau/nouveau_backlight.c index d1c998e645fb4b6..f0856adbe775624 100644 --- a/drivers/gpu/drm/nouveau/nouveau_backlight.c +++ b/drivers/gpu/drm/nouveau/nouveau_backlight.c @@ -47,20 +47,20 @@ struct nouveau_backlight { int id; };
-static bool +static int nouveau_get_backlight_name(char backlight_name[BL_NAME_SIZE], struct nouveau_backlight *bl) { int nb = ida_simple_get(&bl_ida, 0, 100, GFP_KERNEL);
if (nb < 0)
- return false;
- return nb;
if (nb > 0) snprintf(backlight_name, BL_NAME_SIZE, "nv_backlight%d", nb); else snprintf(backlight_name, BL_NAME_SIZE, "nv_backlight"); bl->id = nb;
- return true;
- return 0;
}
static int @@ -273,7 +273,8 @@ nouveau_backlight_init(struct drm_connector *connector) if (!bl) return -ENOMEM;
- if (!nouveau_get_backlight_name(backlight_name, bl)) {
- ret = nouveau_get_backlight_name(backlight_name, bl);
- if (ret) {
NV_ERROR(drm, "Failed to retrieve a unique name for the backlight interface\n"); goto fail_alloc; } -- 2.26.0.106.g9fadedd
Nouveau mailing list Nouveau@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/nouveau
Message: 4 Date: Wed, 12 May 2021 08:39:52 +0200 From: Pierre Moreau pierre.morrow@free.fr To: Zhen Lei thunder.leizhen@huawei.com Cc: Ben Skeggs bskeggs@redhat.com, David Airlie airlied@linux.ie, Daniel Vetter daniel@ffwll.ch, dri-devel dri-devel@lists.freedesktop.org, nouveau nouveau@lists.freedesktop.org Subject: Re: [Nouveau] [PATCH v2 1/2] drm/nouveau: Fix ida leak Message-ID: 20210512063952.5kwdrq2yzbmgmn4x@Normandy.localdomain Content-Type: text/plain; charset=utf-8
Why remove the const modifier on `nb`?
On 2021-05-11 ? 16:28, Zhen Lei wrote:
When the 'nb' value allocated from 'bl_ida' is greater than or equal to 100, it will not be released. In fact, we can simplify operations by limiting the range of idas that can be applied for.
By the way, delete the const modifier of the local variable 'nb'.
Fixes: db1a0ae21461 ("drm/nouveau/bl: Assign different names to interfaces") Signed-off-by: Zhen Lei thunder.leizhen@huawei.com
drivers/gpu/drm/nouveau/nouveau_backlight.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/nouveau/nouveau_backlight.c b/drivers/gpu/drm/nouveau/nouveau_backlight.c index 72f35a2babcb20e..d1c998e645fb4b6 100644 --- a/drivers/gpu/drm/nouveau/nouveau_backlight.c +++ b/drivers/gpu/drm/nouveau/nouveau_backlight.c @@ -51,8 +51,9 @@ static bool nouveau_get_backlight_name(char backlight_name[BL_NAME_SIZE], struct nouveau_backlight *bl) {
- const int nb = ida_simple_get(&bl_ida, 0, 0, GFP_KERNEL);
- if (nb < 0 || nb >= 100)
- int nb = ida_simple_get(&bl_ida, 0, 100, GFP_KERNEL);
- if (nb < 0)
return false; if (nb > 0) snprintf(backlight_name, BL_NAME_SIZE, "nv_backlight%d", nb); -- 2.26.0.106.g9fadedd
Nouveau mailing list Nouveau@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/nouveau
Message: 5 Date: Wed, 12 May 2021 08:44:10 +0200 From: Gerd Hoffmann kraxel@redhat.com To: "Kasireddy, Vivek" vivek.kasireddy@intel.com Cc: "dri-devel@lists.freedesktop.org" dri-devel@lists.freedesktop.org Subject: Re: [PATCH 1/3] virtio-gpu uapi: Add VIRTIO_GPU_F_EXPLICIT_FLUSH feature Message-ID: 20210512064410.infyhtac2bc35xr4@sirius.home.kraxel.org Content-Type: text/plain; charset=us-ascii
Hi,
However, as part of this feature (explicit flush), I'd like to make the Guest wait until the current resource (as specified by resource_flush or set_scanout) is flushed or synchronized. But for a different feature I am thinking of (explicit sync), I'd like to make the Guest wait for the previous buffer/resource submitted (available via old_state->fb).
For page-flipping I guess? i.e. you want submit a new framebuffer, then wait until the host doesn't need the previous one? That is likewise linked to a command, although it is set_scanout this time.
So, right now qemu simply queues the request and completes the command when a guest sends a resource_flush our set_scanout command. You want be notified when the host is actually done processing the request.
I still think it makes sense extend the resource_flush and set_scanout commands for that, for example by adding a flag for the flags field in the request header. That way it is clear what exactly you are waiting for. You can also attach a fence to the request which you can later wait on.
take care, Gerd
Message: 6 Date: Wed, 12 May 2021 14:57:23 +0800 From: "Leizhen (ThunderTown)" thunder.leizhen@huawei.com To: Ben Skeggs bskeggs@redhat.com, David Airlie airlied@linux.ie, "Daniel Vetter" daniel@ffwll.ch, dri-devel dri-devel@lists.freedesktop.org, nouveau nouveau@lists.freedesktop.org Subject: Re: [Nouveau] [PATCH v2 1/2] drm/nouveau: Fix ida leak Message-ID: 0800f5b6-ff18-94eb-a4a0-113800a9b14d@huawei.com Content-Type: text/plain; charset="utf-8"
On 2021/5/12 14:39, Pierre Moreau wrote:
Why remove the const modifier on `nb`?
A non-pointer local variable, I don't think it's necessary to add const modifier to make the syntax too complicated.
On 2021-05-11 ? 16:28, Zhen Lei wrote:
When the 'nb' value allocated from 'bl_ida' is greater than or equal to 100, it will not be released. In fact, we can simplify operations by limiting the range of idas that can be applied for.
By the way, delete the const modifier of the local variable 'nb'.
Fixes: db1a0ae21461 ("drm/nouveau/bl: Assign different names to interfaces") Signed-off-by: Zhen Lei thunder.leizhen@huawei.com
drivers/gpu/drm/nouveau/nouveau_backlight.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/nouveau/nouveau_backlight.c b/drivers/gpu/drm/nouveau/nouveau_backlight.c index 72f35a2babcb20e..d1c998e645fb4b6 100644 --- a/drivers/gpu/drm/nouveau/nouveau_backlight.c +++ b/drivers/gpu/drm/nouveau/nouveau_backlight.c @@ -51,8 +51,9 @@ static bool nouveau_get_backlight_name(char backlight_name[BL_NAME_SIZE], struct nouveau_backlight *bl) {
- const int nb = ida_simple_get(&bl_ida, 0, 0, GFP_KERNEL);
- if (nb < 0 || nb >= 100)
- int nb = ida_simple_get(&bl_ida, 0, 100, GFP_KERNEL);
- if (nb < 0)
return false; if (nb > 0) snprintf(backlight_name, BL_NAME_SIZE, "nv_backlight%d", nb); -- 2.26.0.106.g9fadedd
Nouveau mailing list Nouveau@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/nouveau
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