On Nov 21, 2023, at 21:14, Conor Dooley <conor.dooley@xxxxxxxxxxxxx> wrote: > On Tue, Nov 21, 2023 at 06:55:07PM +0800, Jerry Shih wrote: >> Sorry, I just use my `internal` qemu with vector-crypto and rva22 patches. >> >> The public qemu haven't supported rva22 profiles. Here is the qemu patch[1] for >> that. But here is the discussion why the qemu doesn't export these >> `named extensions`(e.g. Zicclsm). >> I try to add Zicclsm in DT in the v2 patch set. Maybe we will have more discussion >> about the rva22 profiles in kernel DT. > > Please do, that'll be fun! Please take some time to read what the > profiles spec actually defines Zicclsm fore before you send those patches > though. I think you might come to find you have misunderstood what it > means - certainly I did the first time I saw it! >From the rva22 profile: This requires misaligned support for all regular load and store instructions (including scalar and ``vector``) The spec includes the explicit `vector` keyword. So, I still think we could use Zicclsm checking for these vector-crypto implementations. My proposed patch is just a simple patch which only update the DT document and update the isa string parser for Zicclsm. If it's still not recommend to use Zicclsm checking, I will turn to use `RISCV_HWPROBE_MISALIGNED_*` instead. >> [1] >> LINK: https://lore.kernel.org/all/d1d6f2dc-55b2-4dce-a48a-4afbbf6df526@xxxxxxxxxxxxxxxx/#t >> >> I don't know whether it's a good practice to check unaligned access using >> `Zicclsm`. >> >> Here is another related cpu feature for unaligned access: >> RISCV_HWPROBE_MISALIGNED_* >> But it looks like it always be initialized with `RISCV_HWPROBE_MISALIGNED_SLOW`[2]. >> It implies that linux kernel always supports unaligned access. But we have the >> actual HW which doesn't support unaligned access for vector unit. > > https://docs.kernel.org/arch/riscv/uabi.html#misaligned-accesses > > Misaligned accesses are part of the user ABI & the hwprobe stuff for > that allows userspace to figure out whether they're fast (likely > implemented in hardware), slow (likely emulated in firmware) or emulated > in the kernel. The HWPROBE_MISALIGNED_* checking function is at: https://github.com/torvalds/linux/blob/c2d5304e6c648ebcf653bace7e51e0e6742e46c8/arch/riscv/kernel/cpufeature.c#L564-L647 The tests are all scalar. No `vector` test inside. So, I'm not sure the HWPROBE_MISALIGNED_* is related to vector unit or not. The goal is to check whether `vector` support unaligned access or not in this crypto patch. I haven't seen the emulated path for unaligned-vector-access in OpenSBI and kernel. Is the unaligned-vector-access included in user ABI? Thanks, Jerry
