[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20240412-dwarf-shower-5a7300fcd283@wendy>
Date: Fri, 12 Apr 2024 12:49:57 +0100
From: Conor Dooley <conor.dooley@...rochip.com>
To: Charlie Jenkins <charlie@...osinc.com>
CC: Conor Dooley <conor@...nel.org>, Rob Herring <robh@...nel.org>, Krzysztof
Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Paul Walmsley
<paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, Albert Ou
<aou@...s.berkeley.edu>, Guo Ren <guoren@...nel.org>, Conor Dooley
<conor+dt@...nel.org>, Chen-Yu Tsai <wens@...e.org>, Jernej Skrabec
<jernej.skrabec@...il.com>, Samuel Holland <samuel@...lland.org>, Evan Green
<evan@...osinc.com>, Clément Léger
<cleger@...osinc.com>, Jonathan Corbet <corbet@....net>, Shuah Khan
<shuah@...nel.org>, <linux-riscv@...ts.infradead.org>,
<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Palmer Dabbelt
<palmer@...osinc.com>, <linux-arm-kernel@...ts.infradead.org>,
<linux-sunxi@...ts.linux.dev>, <linux-doc@...r.kernel.org>,
<linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH 08/19] riscv: Introduce vendor variants of extension
helpers
On Thu, Apr 11, 2024 at 09:11:14PM -0700, Charlie Jenkins wrote:
> Create vendor variants of the existing extension helpers. If the
> existing functions were instead modified to support vendor extensions, a
> branch based on the ext value being greater than
> RISCV_ISA_VENDOR_EXT_BASE would have to be introduced. This additional
> branch would have an unnecessary performance impact.
>
> Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
I've not looked at the "main" patch in the series that adds all of the
probing and structures for representing this info yet beyond a cursory
glance, but it feels like we're duplicating a bunch of infrastructure
here before it is necessary. The IDs are all internal to Linux, so I'd
rather we kept everything in the same structure until we have more than
a handful of vendor extensions. With this patch (and the theadpmu stuff)
we will have three vendor extensions which feels like a drop in the
bucket compared to the standard ones.
> ---
> arch/riscv/include/asm/cpufeature.h | 54 +++++++++++++++++++++++++++++++++++++
> arch/riscv/kernel/cpufeature.c | 34 ++++++++++++++++++++---
> 2 files changed, 84 insertions(+), 4 deletions(-)
>
> diff --git a/arch/riscv/include/asm/cpufeature.h b/arch/riscv/include/asm/cpufeature.h
> index db2ab037843a..8f19e3681b4f 100644
> --- a/arch/riscv/include/asm/cpufeature.h
> +++ b/arch/riscv/include/asm/cpufeature.h
> @@ -89,6 +89,10 @@ bool __riscv_isa_extension_available(const unsigned long *isa_bitmap, unsigned i
> #define riscv_isa_extension_available(isa_bitmap, ext) \
> __riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_##ext)
>
> +bool __riscv_isa_vendor_extension_available(const unsigned long *vendor_isa_bitmap, unsigned int bit);
> +#define riscv_isa_vendor_extension_available(isa_bitmap, ext) \
> + __riscv_isa_vendor_extension_available(isa_bitmap, RISCV_ISA_VENDOR_EXT_##ext)
> +
> static __always_inline bool
> __riscv_has_extension_likely_alternatives(const unsigned long ext)
> {
> @@ -117,6 +121,8 @@ __riscv_has_extension_unlikely_alternatives(const unsigned long ext)
> return true;
> }
>
> +/* Standard extension helpers */
> +
> static __always_inline bool
> riscv_has_extension_likely(const unsigned long ext)
> {
> @@ -163,4 +169,52 @@ static __always_inline bool riscv_cpu_has_extension_unlikely(int cpu, const unsi
> return __riscv_isa_extension_available(hart_isa[cpu].isa, ext);
> }
>
> +/* Vendor extension helpers */
> +
> +static __always_inline bool
> +riscv_has_vendor_extension_likely(const unsigned long ext)
> +{
> + compiletime_assert(ext < RISCV_ISA_VENDOR_EXT_MAX,
> + "ext must be < RISCV_ISA_VENDOR_EXT_MAX");
> +
> + if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE))
> + return __riscv_has_extension_likely_alternatives(ext);
> + else
> + return __riscv_isa_vendor_extension_available(NULL, ext);
> +}
> +
> +static __always_inline bool
> +riscv_has_vendor_extension_unlikely(const unsigned long ext)
> +{
> + compiletime_assert(ext < RISCV_ISA_VENDOR_EXT_MAX,
> + "ext must be < RISCV_ISA_VENDOR_EXT_MAX");
> +
> + if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE))
> + return __riscv_has_extension_unlikely_alternatives(ext);
> + else
> + return __riscv_isa_vendor_extension_available(NULL, ext);
> +}
> +
> +static __always_inline bool riscv_cpu_has_vendor_extension_likely(int cpu, const unsigned long ext)
> +{
> + compiletime_assert(ext < RISCV_ISA_VENDOR_EXT_MAX,
> + "ext must be < RISCV_ISA_VENDOR_EXT_MAX");
> +
> + if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE))
> + return __riscv_has_extension_likely_alternatives(ext);
> + else
> + return __riscv_isa_vendor_extension_available(hart_isa_vendor[cpu].isa, ext);
> +}
> +
> +static __always_inline bool riscv_cpu_has_vendor_extension_unlikely(int cpu, const unsigned long ext)
> +{
> + compiletime_assert(ext < RISCV_ISA_VENDOR_EXT_MAX,
> + "ext must be < RISCV_ISA_VENDOR_EXT_MAX");
> +
> + if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE))
> + return __riscv_has_extension_unlikely_alternatives(ext);
> + else
> + return __riscv_isa_vendor_extension_available(hart_isa_vendor[cpu].isa, ext);
> +}
Same stuff about constant folding applies to these, I think these should
just mirror the existing functions (if needed at all).
Cheers,
Conor.
Download attachment "signature.asc" of type "application/pgp-signature" (229 bytes)
Powered by blists - more mailing lists