linux-kernel - Re: [PATCH v3 0/4] riscv: Separate vendor extensions from standard extensions

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Message-ID: <20240722-0c2488245ce33131693c6d34@orel>
Date: Mon, 22 Jul 2024 14:32:49 -0500
From: Andrew Jones <ajones@...tanamicro.com>
To: Charlie Jenkins <charlie@...osinc.com>
Cc: Paul Walmsley <paul.walmsley@...ive.com>, 
	Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
	Conor Dooley <conor.dooley@...rochip.com>, Evan Green <evan@...osinc.com>, Andy Chiu <andy.chiu@...ive.com>, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	Yu Chien Peter Lin <peterlin@...estech.com>
Subject: Re: [PATCH v3 0/4] riscv: Separate vendor extensions from standard
 extensions

On Fri, Jul 19, 2024 at 09:15:17AM GMT, Charlie Jenkins wrote:
> All extensions, both standard and vendor, live in one struct
> "riscv_isa_ext". There is currently one vendor extension, xandespmu, but
> it is likely that more vendor extensions will be added to the kernel in
> the future. As more vendor extensions (and standard extensions) are
> added, riscv_isa_ext will become more bloated with a mix of vendor and
> standard extensions.

But the mix doesn't hurt and with everything in one place it makes it easy
to know where to look.

> 
> This also allows each vendor to be conditionally enabled through
> Kconfig.

We can do that anyway by adding an extension menu for each vendor. If we
don't want a vendor's extensions bloating the array then we just need
some #ifdefs, e.g.

@@ -405,7 +405,9 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
        __RISCV_ISA_EXT_DATA(svinval, RISCV_ISA_EXT_SVINVAL),
        __RISCV_ISA_EXT_DATA(svnapot, RISCV_ISA_EXT_SVNAPOT),
        __RISCV_ISA_EXT_DATA(svpbmt, RISCV_ISA_EXT_SVPBMT),
+#ifdef RISCV_ISA_VENDOR_EXT_ANDES
        __RISCV_ISA_EXT_DATA(xandespmu, RISCV_ISA_EXT_XANDESPMU),
+#endif
 };


So, I'm not convinced we want the additional complexity of vendor
extension arrays, but maybe I'm missing something.

Thanks,
drew