[v9, 00/10] riscv: support kernel-mode Vector

[Palmer Dabbelt]

On Sun, 07 Jan 2024 19:52:09 PST (-0800), ebiggers at kernel.org wrote:
> On Mon, Jan 08, 2024 at 11:16:27AM +0800, Andy Chiu wrote:
>> On Sat, Jan 6, 2024 at 2:59 AM Eric Biggers <ebiggers at kernel.org> wrote:
>> >
>> > Hi Palmer,
>> >
>> > On Fri, Dec 29, 2023 at 02:36:17PM +0000, Andy Chiu wrote:
>> > > This series provides support running Vector in kernel mode.
>> >
>> > Is there any chance that you can take patches 1 and 2 of this series via the
>> > RISC-V tree for v6.8?  The vector crypto patchset depends on those two patches.
>> 
>> Patch 4 is very essential for non-preemptible kernel-mode Vector,
>> unless we want to bear restoring overhead at each kernel_vector_end().
>> It's ~200 cycles on a VLEN=128 hardware. It happens as long as Vector
>> is also used in user-mode, which will be very common. Please consider
>> including up to patch 4 if we must split.
>> 
>
> It's definitely an important optimization, but I wouldn't call it "very
> essential".  x86 didn't implement lazy restores until kernel v5.2.
>
> My hope is that we can just get enough merged soon to unblock the vector crypto
> patchset, which just needs kernel_vector_{begin,end} with softirq support.  The
> remaining core vector work can happen in parallel.

Andy says he's going to send a v10 tomorrow, I'll plan on merging that.

>
> - Eric
>
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