Re: [Intel-gfx] Commit messages
Dear Christian, dear Daniel, dear Alex, Am 23.03.22 um 16:32 schrieb Christian König: Am 23.03.22 um 16:24 schrieb Daniel Stone: On Wed, 23 Mar 2022 at 15:14, Alex Deucher wrote: On Wed, Mar 23, 2022 at 11:04 AM Daniel Stone wrote: That's not what anyone's saying here ... No-one's demanding AMD publish RTL, or internal design docs, or hardware specs, or URLs to JIRA tickets no-one can access. This is a large and invasive commit with pretty big ramifications; containing exactly two lines of commit message, one of which just duplicates the subject. It cannot be the case that it's completely impossible to provide any justification, background, or details, about this commit being made. Unless, of course, it's to fix a non-public security issue, that is reasonable justification for eliding some of the details. But then again, 'huge change which is very deliberately opaque' is a really good way to draw a lot of attention to the commit, and it would be better to provide more detail about the change to help it slip under the radar. If dri-devel@ isn't allowed to inquire about patches which are posted, then CCing the list is just a façade; might as well just do it all internally and periodically dump out pull requests. I think we are in agreement. I think the withheld information Christian was referring to was on another thread with Christian and Paul discussing a workaround for a hardware bug: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.spinics.net%2Flists%2Famd-gfx%2Fmsg75908.htmldata=04%7C01%7Cchristian.koenig%40amd.com%7C6a3f2815d83b4872577008da0ce1347a%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637836458652370599%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000sdata=QtNB0XHMhTgH%2FNHMwF23Qn%2BgSdYyHJSenbpP%2FHG%2BkxE%3Dreserved=0 (Thank you Microsoft for keeping us safe.) I guess it proves, how assuming what other people should know/have read, especially when crossing message threads, is causing confusion and misunderstandings. Right, that definitely seems like some crossed wires. I don't see anything wrong with that commit at all: the commit message and a comment notes that there is a hardware issue preventing Raven from being able to do TMZ+GTT, and the code does the very straightforward and obvious thing to ensure that on VCN 1.0, any TMZ buffer must be VRAM-placed. My questions were: Where is that documented, and how can this be reproduced? Shouldn’t these be answered by the commit message? In five(?) years, somebody, maybe even with access to the currently non-public documents, finds a fault in the commit, and would be helped by having an document/errata number where to look at. To verify the fix, the developer would need a method to produce the error, so why not just share it? Also, I assume that workarounds often come with downsides, as otherwise it would have been programmed like this from the beginning, or instead of “workaround” it would be called “improvement”. Shouldn’t that also be answered? So totally made-up example: Currently, there is a graphics corruption running X on system Y. This is caused by a hardware bug in Raven ASIC (details internal document #/AMD-Jira #N), and can be worked around by [what is in the commit message]. The workaround does not affect the performance, and testing X shows the error is fixed. This one, on the other hand, is much less clear ... Yes, completely agree. I mean a good bunch of comments on commit messages are certainly valid and we could improve them. That’d be great. But this patch here was worked on by both AMD and Intel developers. Where both sides and I think even people from other companies perfectly understands why, what, how etc... When now somebody comes along and asks for a whole explanation of the context why we do it then that sounds really strange to me. The motivation should be part of the commit message. I didn’t mean anyone to rewrite buddy memory allocator Wikipedia article [1]. But the commit message at hand for switching the allocator is definitely too terse. Kind regards, Paul [1]: https://en.wikipedia.org/wiki/Buddy_memory_allocation
Re: [Intel-gfx] Commit messages (was: [PATCH v11] drm/amdgpu: add drm buddy support to amdgpu)
On Wed, 23 Mar 2022 at 16:32, Christian König wrote: > > Am 23.03.22 um 16:24 schrieb Daniel Stone: > > On Wed, 23 Mar 2022 at 15:14, Alex Deucher wrote: > >> On Wed, Mar 23, 2022 at 11:04 AM Daniel Stone wrote: > >>> That's not what anyone's saying here ... > >>> > >>> No-one's demanding AMD publish RTL, or internal design docs, or > >>> hardware specs, or URLs to JIRA tickets no-one can access. > >>> > >>> This is a large and invasive commit with pretty big ramifications; > >>> containing exactly two lines of commit message, one of which just > >>> duplicates the subject. > >>> > >>> It cannot be the case that it's completely impossible to provide any > >>> justification, background, or details, about this commit being made. > >>> Unless, of course, it's to fix a non-public security issue, that is > >>> reasonable justification for eliding some of the details. But then > >>> again, 'huge change which is very deliberately opaque' is a really > >>> good way to draw a lot of attention to the commit, and it would be > >>> better to provide more detail about the change to help it slip under > >>> the radar. > >>> > >>> If dri-devel@ isn't allowed to inquire about patches which are posted, > >>> then CCing the list is just a façade; might as well just do it all > >>> internally and periodically dump out pull requests. > >> I think we are in agreement. I think the withheld information > >> Christian was referring to was on another thread with Christian and > >> Paul discussing a workaround for a hardware bug: > >> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.spinics.net%2Flists%2Famd-gfx%2Fmsg75908.htmldata=04%7C01%7Cchristian.koenig%40amd.com%7C6a3f2815d83b4872577008da0ce1347a%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637836458652370599%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000sdata=QtNB0XHMhTgH%2FNHMwF23Qn%2BgSdYyHJSenbpP%2FHG%2BkxE%3Dreserved=0 > > Right, that definitely seems like some crossed wires. I don't see > > anything wrong with that commit at all: the commit message and a > > comment notes that there is a hardware issue preventing Raven from > > being able to do TMZ+GTT, and the code does the very straightforward > > and obvious thing to ensure that on VCN 1.0, any TMZ buffer must be > > VRAM-placed. > > > > This one, on the other hand, is much less clear ... > > Yes, completely agree. I mean a good bunch of comments on commit > messages are certainly valid and we could improve them. > > But this patch here was worked on by both AMD and Intel developers. > Where both sides and I think even people from other companies perfectly > understands why, what, how etc... > > When now somebody comes along and asks for a whole explanation of the > context why we do it then that sounds really strange to me. Yeah gpus are using pages a lot more like the cpu (with bigger pages of benefit, but not required, hence the buddy allocator to coalesce them), and extremely funny contig allocations with bonkers requirements aren't needed anymore (which was the speciality of drm_mm.c). Hence why both i915 and amdgpu move over to this new buddy allocator for managing vram. I guess that could be added to the commit message, but also it's kinda well known - the i915 patches also didn't explain why we want to manage our vram with a buddy allocator (I think some of the earlier versions explained it a bit, but the version with ttm integration that landed didnt). But yeah the confusing comments about hiding stuff that somehow spilled over from other discussions into this didn't help :-/ -Daniel > Thanks for jumping in here, > Christian. > > > > > Cheers, > > Daniel > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
Re: [Intel-gfx] Commit messages (was: [PATCH v11] drm/amdgpu: add drm buddy support to amdgpu)
On Wed, 23 Mar 2022 at 15:14, Alex Deucher wrote: > On Wed, Mar 23, 2022 at 11:04 AM Daniel Stone wrote: > > That's not what anyone's saying here ... > > > > No-one's demanding AMD publish RTL, or internal design docs, or > > hardware specs, or URLs to JIRA tickets no-one can access. > > > > This is a large and invasive commit with pretty big ramifications; > > containing exactly two lines of commit message, one of which just > > duplicates the subject. > > > > It cannot be the case that it's completely impossible to provide any > > justification, background, or details, about this commit being made. > > Unless, of course, it's to fix a non-public security issue, that is > > reasonable justification for eliding some of the details. But then > > again, 'huge change which is very deliberately opaque' is a really > > good way to draw a lot of attention to the commit, and it would be > > better to provide more detail about the change to help it slip under > > the radar. > > > > If dri-devel@ isn't allowed to inquire about patches which are posted, > > then CCing the list is just a façade; might as well just do it all > > internally and periodically dump out pull requests. > > I think we are in agreement. I think the withheld information > Christian was referring to was on another thread with Christian and > Paul discussing a workaround for a hardware bug: > https://www.spinics.net/lists/amd-gfx/msg75908.html Right, that definitely seems like some crossed wires. I don't see anything wrong with that commit at all: the commit message and a comment notes that there is a hardware issue preventing Raven from being able to do TMZ+GTT, and the code does the very straightforward and obvious thing to ensure that on VCN 1.0, any TMZ buffer must be VRAM-placed. This one, on the other hand, is much less clear ... Cheers, Daniel
Re: [Intel-gfx] Commit messages (was: [PATCH v11] drm/amdgpu: add drm buddy support to amdgpu)
On Wed, Mar 23, 2022 at 11:04 AM Daniel Stone wrote: > > Hi Alex, > > On Wed, 23 Mar 2022 at 14:42, Alex Deucher wrote: > > On Wed, Mar 23, 2022 at 10:00 AM Daniel Stone wrote: > > > On Wed, 23 Mar 2022 at 08:19, Christian König > > > wrote: > > > > Well the key point is it's not about you to judge that. > > > > > > > > If you want to complain about the commit message then come to me with > > > > that and don't request information which isn't supposed to be publicly > > > > available. > > > > > > > > So to make it clear: The information is intentionally hold back and not > > > > made public. > > > > > > In that case, the code isn't suitable to be merged into upstream > > > trees; it can be resubmitted when it can be explained. > > > > So you are saying we need to publish the problematic RTL to be able to > > fix a HW bug in the kernel? That seems a little unreasonable. Also, > > links to internal documents or bug trackers don't provide much value > > to the community since they can't access them. In general, adding > > internal documents to commit messages is frowned on. > > That's not what anyone's saying here ... > > No-one's demanding AMD publish RTL, or internal design docs, or > hardware specs, or URLs to JIRA tickets no-one can access. > > This is a large and invasive commit with pretty big ramifications; > containing exactly two lines of commit message, one of which just > duplicates the subject. > > It cannot be the case that it's completely impossible to provide any > justification, background, or details, about this commit being made. > Unless, of course, it's to fix a non-public security issue, that is > reasonable justification for eliding some of the details. But then > again, 'huge change which is very deliberately opaque' is a really > good way to draw a lot of attention to the commit, and it would be > better to provide more detail about the change to help it slip under > the radar. > > If dri-devel@ isn't allowed to inquire about patches which are posted, > then CCing the list is just a façade; might as well just do it all > internally and periodically dump out pull requests. I think we are in agreement. I think the withheld information Christian was referring to was on another thread with Christian and Paul discussing a workaround for a hardware bug: https://www.spinics.net/lists/amd-gfx/msg75908.html Alex Alex
Re: [Intel-gfx] Commit messages (was: [PATCH v11] drm/amdgpu: add drm buddy support to amdgpu)
Hi Alex, On Wed, 23 Mar 2022 at 14:42, Alex Deucher wrote: > On Wed, Mar 23, 2022 at 10:00 AM Daniel Stone wrote: > > On Wed, 23 Mar 2022 at 08:19, Christian König > > wrote: > > > Well the key point is it's not about you to judge that. > > > > > > If you want to complain about the commit message then come to me with > > > that and don't request information which isn't supposed to be publicly > > > available. > > > > > > So to make it clear: The information is intentionally hold back and not > > > made public. > > > > In that case, the code isn't suitable to be merged into upstream > > trees; it can be resubmitted when it can be explained. > > So you are saying we need to publish the problematic RTL to be able to > fix a HW bug in the kernel? That seems a little unreasonable. Also, > links to internal documents or bug trackers don't provide much value > to the community since they can't access them. In general, adding > internal documents to commit messages is frowned on. That's not what anyone's saying here ... No-one's demanding AMD publish RTL, or internal design docs, or hardware specs, or URLs to JIRA tickets no-one can access. This is a large and invasive commit with pretty big ramifications; containing exactly two lines of commit message, one of which just duplicates the subject. It cannot be the case that it's completely impossible to provide any justification, background, or details, about this commit being made. Unless, of course, it's to fix a non-public security issue, that is reasonable justification for eliding some of the details. But then again, 'huge change which is very deliberately opaque' is a really good way to draw a lot of attention to the commit, and it would be better to provide more detail about the change to help it slip under the radar. If dri-devel@ isn't allowed to inquire about patches which are posted, then CCing the list is just a façade; might as well just do it all internally and periodically dump out pull requests. Cheers, Daniel
Re: [Intel-gfx] Commit messages (was: [PATCH v11] drm/amdgpu: add drm buddy support to amdgpu)
On Wed, Mar 23, 2022 at 10:00 AM Daniel Stone wrote: > > On Wed, 23 Mar 2022 at 08:19, Christian König > wrote: > > Am 23.03.22 um 09:10 schrieb Paul Menzel: > > > Sorry, I disagree. The motivation needs to be part of the commit > > > message. For example see recent discussion on the LWN article > > > *Donenfeld: Random number generator enhancements for Linux 5.17 and > > > 5.18* [1]. > > > > > > How much the commit message should be extended, I do not know, but the > > > current state is insufficient (too terse). > > > > Well the key point is it's not about you to judge that. > > > > If you want to complain about the commit message then come to me with > > that and don't request information which isn't supposed to be publicly > > available. > > > > So to make it clear: The information is intentionally hold back and not > > made public. > > In that case, the code isn't suitable to be merged into upstream > trees; it can be resubmitted when it can be explained. So you are saying we need to publish the problematic RTL to be able to fix a HW bug in the kernel? That seems a little unreasonable. Also, links to internal documents or bug trackers don't provide much value to the community since they can't access them. In general, adding internal documents to commit messages is frowned on. Alex
Re: [Intel-gfx] Commit messages (was: [PATCH v11] drm/amdgpu: add drm buddy support to amdgpu)
On Wed, 23 Mar 2022 at 08:19, Christian König wrote: > Am 23.03.22 um 09:10 schrieb Paul Menzel: > > Sorry, I disagree. The motivation needs to be part of the commit > > message. For example see recent discussion on the LWN article > > *Donenfeld: Random number generator enhancements for Linux 5.17 and > > 5.18* [1]. > > > > How much the commit message should be extended, I do not know, but the > > current state is insufficient (too terse). > > Well the key point is it's not about you to judge that. > > If you want to complain about the commit message then come to me with > that and don't request information which isn't supposed to be publicly > available. > > So to make it clear: The information is intentionally hold back and not > made public. In that case, the code isn't suitable to be merged into upstream trees; it can be resubmitted when it can be explained. Cheers, Daniel
