On Tue, Nov 7, 2023 at 5:42 PM François Beaufort <fbeauf...@google.com> wrote:
> > > On Mon, Oct 30, 2023 at 7:39 PM Mike Taylor <miketa...@chromium.org> > wrote: > >> On 10/30/23 12:59 PM, Corentin Wallez wrote: >> >> On Fri, Oct 27, 2023 at 2:19 AM Domenic Denicola <dome...@chromium.org> >> wrote: >> >>> >>> >>> On Thu, Oct 26, 2023 at 7:21 PM François Beaufort <fbeauf...@google.com> >>> wrote: >>> >>>> >>>> >>>> On Thu, Oct 26, 2023 at 11:05 AM Domenic Denicola <dome...@chromium.org> >>>> wrote: >>>> >>>>> >>>>> >>>>> On Thu, Oct 26, 2023 at 5:21 PM 'François Beaufort' via blink-dev < >>>>> blink-dev@chromium.org> wrote: >>>>> >>>>>> Contact emails >>>>>> >>>>>> fbeauf...@google.com, cwal...@google.com >>>>>> >>>>>> Explainer >>>>>> >>>>>> https://github.com/gpuweb/gpuweb/issues/614 >>>>>> >>>>>> Specification >>>>>> >>>>>> https://gpuweb.github.io/gpuweb/#timestamp >>>>>> >>>>>> Summary >>>>>> >>>>>> WebGPU timestamp queries allow WebGPU applications to measure >>>>>> precisely (down to the nanosecond) how much time their GPU commands take >>>>>> to >>>>>> execute, especially at the beginning and end of passes. Timestamp queries >>>>>> are heavily used to gain insights into the performance and behavior of >>>>>> GPU >>>>>> workloads. >>>>>> >>>>>> While the WebGPU specification makes timestamp queries an optional >>>>>> feature due to timing attack concerns, we believe that timestamp queries >>>>>> quantization provides a good middle ground by reducing the precision of >>>>>> timers. To offer even more advanced protection against timing attacks and >>>>>> fingerprinting, timestamp queries are also coarsened based on site >>>>>> isolation status: >>>>>> >>>>>> - Isolated contexts: timestamp queries are exposed with a resolution >>>>>> of 100 microseconds. >>>>>> >>>>>> - Non-isolated contexts: timestamp queries are not exposed at all. >>>>>> >>>>> >>>>> By "isolated" do you mean "has the cross-origin isolated capability >>>>> <https://html.spec.whatwg.org/#concept-settings-object-cross-origin-isolated-capability> >>>>> "? >>>>> >>>> >>>> Yes. >>>> >>>> >>>>> >>>>> I wasn't able to find any spec or tests for this requirement, which >>>>> seems like a potential interoperability issue. >>>>> >>>> >>>> The WebGPU spec currently says: "The feature is optional, and a WebGPU >>>> implementation may limit its exposure only to those scenarios that are >>>> trusted." >>>> See >>>> https://gpuweb.github.io/gpuweb/#security-timing:~:text=The%20feature%20is%20optional%2C%20and%20a%20WebGPU%20implementation%20may%20limit%20its%20exposure%20only%20to%20those%20scenarios%20that%20are%20trusted >>>> >>> >>> I realize that. I was suggesting that, for interoperability purposes, >>> you should consider specifying the actual condition, instead of leaving it >>> vague and optional. (E.g. at least in other standards bodies, we have >>> guidance to avoid optional or implementation-defined features; instead, we >>> try to work together with other browser engines to come to a common, >>> interoperable implementation, backed by a test suite.) >>> >>> I hope the API Owners can consider this when deciding whether or not to >>> approve, as I believe that letting these sorts of non-specified and >>> non-tested features be shipped is harmful for the platform's health. >>> >>> >> I'll add discussion of that to the agenda for this week's WebGPU meeting: >> can we agree on the availability of timestamp queries (provided there is >> hardware support) and the quantization depending on contexts. (but to be >> perfectly honest I think we'll have pushback). Of course the WebGPU >> standard body tries to avoid implementation-defined features, and instead >> have deterministic and tested features, but timestamps is one of the ones >> that might need to be an exception to it. Let's see what consensus the >> group comes to! >> >> >> Thank you - looking forward to the update. >> > > Good news! The members of the GPU for the Web Community Group have accepted > a proposal > <https://github.com/gpuweb/gpuweb/issues/4175#issuecomment-1789865938> to > allow timestamps regardless of site isolation, always with the non-isolated > resolution from hr-time <https://w3c.github.io/hr-time/#dfn-coarsen-time> > (100us). > Check out the spec PR at https://github.com/gpuweb/gpuweb/pull/4359 and > updated spec at https://gpuweb.github.io/gpuweb/#security-timing. This > decision aims to address the interoperability concerns raised earlier. > That's great! Using the same time resolution as the rest of the platform makes sense, and this definitely addresses my interop concerns. Thanks to you and the group for making this change! -- You received this message because you are subscribed to the Google Groups "blink-dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to blink-dev+unsubscr...@chromium.org. To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM0wra_p2U%2BwqkMrhH12DgMzph_77Ps4xk0Bn_ZspD%2BWEYzuqA%40mail.gmail.com.
