linux-kernel - Re: [PATCH bpf-next v2 2/2] bpf,riscv: Implement bpf_addr_space

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Message-ID: <20240325-creamed-unlovely-4c80082e9b8c@spud>
Date: Mon, 25 Mar 2024 19:40:05 +0000
From: Conor Dooley <conor@...nel.org>
To: Puranjay Mohan <puranjay12@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>,
	Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
	Björn Töpel <bjorn@...nel.org>,
	Luke Nelson <luke.r.nels@...il.com>, Xi Wang <xi.wang@...il.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>, bpf@...r.kernel.org,
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Pu Lehui <pulehui@...weicloud.com>
Subject: Re: [PATCH bpf-next v2 2/2] bpf,riscv: Implement bpf_addr_space_cast
 instruction

On Mon, Mar 25, 2024 at 08:23:18PM +0100, Puranjay Mohan wrote:
> On Mon, Mar 25, 2024 at 8:19 PM Conor Dooley <conor@...nel.org> wrote:
> >
> > On Mon, Mar 25, 2024 at 08:13:10PM +0100, Puranjay Mohan wrote:
> > > On Mon, Mar 25, 2024 at 8:10 PM Conor Dooley <conor@...nel.org> wrote:
> > > >
> > > > On Mon, Mar 25, 2024 at 03:54:34PM +0000, Puranjay Mohan wrote:
> > > > > LLVM generates bpf_addr_space_cast instruction while translating
> > > > > pointers between native (zero) address space and
> > > > > __attribute__((address_space(N))). The addr_space=0 is reserved as
> > > > > bpf_arena address space.
> > > > >
> > > > > rY = addr_space_cast(rX, 0, 1) is processed by the verifier and
> > > > > converted to normal 32-bit move: wX = wY
> > > > >
> > > > > rY = addr_space_cast(rX, 1, 0) has to be converted by JIT.
> > > > >
> > > > > Signed-off-by: Puranjay Mohan <puranjay12@...il.com>
> > > >
> > > > Doesn't compile for allmodconfig:
> > > >   ../arch/riscv/net/bpf_jit_comp64.c:1086:7: error: call to undeclared function 'insn_is_cast_user'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
> > > >
> > > > Cheers,
> > > > Conor.
> > >
> > > Yes,
> > > I mentioned in the cover letter that a patch is required.
> > > It just got merged in bpf-next/master:
> > > https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?id=770546ae9f4c1ae1ebcaf0874f0dd9631d77ec97
> > >
> > > So, rebasing on the latest bpf-next/master should fix the issue.
> >
> > Ah, I see now that there was a mention in the cover letter that I did
> > not see first time around.
> >
> > Bjorn, do you think there's anything we can do about these kinda
> > misleading CI failures for bpf stuff? Some stuff that touches bpf
> > definitely is worth us building, but should we try and build it on top
> > of the bpf tree instead?
> 
> Is there a separate CI for RISCV related stuff? is it public?

It's based outta patchwork, just like the netdev/bpf stuff:
https://patchwork.kernel.org/project/linux-riscv/list/

> I would be interested in adding RISC-V support in
> https://github.com/kernel-patches/bpf
> Is someone already working on this?

If anyone is, it is probably something Bjorn knows about!

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