On Thu, Mar 27, 2025 at 10:27:48AM +0100, Stefano Garzarella wrote: > On Wed, Mar 26, 2025 at 10:37:09PM +0200, Jarkko Sakkinen wrote: > > On Wed, Mar 26, 2025 at 05:58:33PM +0200, Jarkko Sakkinen wrote: > > > On Wed, Mar 26, 2025 at 04:57:47PM +0200, Jarkko Sakkinen wrote: > > > > On Wed, Mar 26, 2025 at 11:34:01AM -0300, Jason Gunthorpe wrote: > > > > > On Wed, Mar 26, 2025 at 02:11:12PM +0200, Jarkko Sakkinen wrote: > > > > > > > > > > > Generally speaking I don't see enough value in complicating > > > > > > callback interface. It's better to handle complications in > > > > > > the leaves (i.e. dictatorship of majority ;-) ). > > > > > > > > > > That is very much not the way most driver subsystems view the > > > > > world. We want to pull logical things into the core code and remove > > > > > them from drivers to make the drivers simpler and more robust. > > > > > > > > > > The amount of really dumb driver boiler plate that this series > > > > > obviously removes is exactly the sort of stuff we should be fixing by > > > > > improving the core code. > > > > > > > > > > The callback interface was never really sanely designed, it was just > > > > > built around the idea of pulling the timout processing into the core > > > > > code for TIS hardware. It should be revised to properly match these > > > > > new HW types that don't have this kind of timeout mechanism. > > > > > > > > Both TIS and CRB, which are TCG standards and they span to many > > > > different types of drivers and busses. I don't have the figures but > > > > probably they cover vast majority of the hardware. > > > > > > > > We are talking about 39 lines of reduced complexity at the cost > > > > of complicating branching at the top level. I doubt that there > > > > is either any throughput or latency issues. > > > > > > > > What is measurable benefit? The rationale is way way too abstract > > > > for me to cope, sorry. > > > > > > E.g., here's how you can get rid of extra cruft in tpm_ftpm_tee w/o > > > any new callbacks. > > Yeah, I agree that your patch should go in any case, with send_recv() or > not. It's a good cleanup. > > > > > Measurable benefit: no need to allocate memory buffer. > > That's right, I read the whole thread before responding, but that's exactly > what I wanted to highlight. Implementing send_recv() we could completely > remove the buffer for the cache here in tpm_ftpm_tee, simplifying it quite a > bit. > > In tpm_svsm instead we allocate it while probing anyway to avoid having to > allocate it every time, but we could potentially do the same (I don't know > if it makes sense honestly). We do this because for SVSM any buffer is fine, > as it can access all guest kernel memory, whereas IIUC for ftpm it has to be > taken from shared memory. > > > > > Let's take that as a starting point ;-) > > Yeah! > > > > > On that basis I can consider this (i.e. something to measure). > > Okay, I explain this better in the commit description for the next version!
Awesome :-) Thanks for the patience with this. I rather precautionaly throw sticks on the road than go through fixes post upstreaming, which is factors more nasty and time-consuming... > > Thanks, > Stefano > BR, Jarkko
