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Date: Fri, 3 Mar 2023 11:55:57 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: WANG Xuerui <kernel@...0n.name>
Cc: Huacai Chen <chenhuacai@...ngson.cn>,
Arnd Bergmann <arnd@...db.de>, loongarch@...ts.linux.dev,
linux-arch@...r.kernel.org, Xuefeng Li <lixuefeng@...ngson.cn>,
Guo Ren <guoren@...nel.org>,
Jiaxun Yang <jiaxun.yang@...goat.com>,
linux-kernel@...r.kernel.org, loongson-kernel@...ts.loongnix.cn
Subject: Re: [PATCH] LoongArch: Fix the CRC32 feature probing
Hi, Xuerui,
On Fri, Mar 3, 2023 at 11:15 AM WANG Xuerui <kernel@...0n.name> wrote:
>
> On 2023/3/3 08:25, Huacai Chen wrote:
> > Not all LoongArch processors support CRC32 instructions, and this feature
> > is indicated by CPUCFG1.CRC32 (Bit25). This bit is wrongly defined in loongarch.h
>
> The ISA manual suggests it's IOCSR_BRD (likely "IOCSR Branding"). You
> have to somehow reconcile the two, either by fixing the manuals, or
> mention here explicitly that the manual is wrong. (Actually thinking
> about it harder now, you may be in fact re-purposing the IOCSR_BRD field
> for CRC32 capability, because all LoongArch cores in existence are
> designed by Loongson, and you may very well know that all cores
> supporting CRC32 have this bit set, and those not having CRC32 haven't.
> If that's the case, please explicitly document this reasoning too.)
The ISA manual has been modified and will be released soon.
>
> > and CRC32 is set unconditionally now, so fix it.
> >
> > BTW, expose the CRC32 feature in /proc/cpuinfo.
> >
> > Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
> > ---
> > arch/loongarch/include/asm/cpu-features.h | 1 +
> > arch/loongarch/include/asm/cpu.h | 40 ++++++++++++-----------
> > arch/loongarch/include/asm/loongarch.h | 2 +-
> > arch/loongarch/kernel/cpu-probe.c | 7 +++-
> > arch/loongarch/kernel/proc.c | 1 +
> > 5 files changed, 30 insertions(+), 21 deletions(-)
> >
> > diff --git a/arch/loongarch/include/asm/cpu-features.h b/arch/loongarch/include/asm/cpu-features.h
> > index b07974218393..f6177f133477 100644
> > --- a/arch/loongarch/include/asm/cpu-features.h
> > +++ b/arch/loongarch/include/asm/cpu-features.h
> > @@ -42,6 +42,7 @@
> > #define cpu_has_fpu cpu_opt(LOONGARCH_CPU_FPU)
> > #define cpu_has_lsx cpu_opt(LOONGARCH_CPU_LSX)
> > #define cpu_has_lasx cpu_opt(LOONGARCH_CPU_LASX)
> > +#define cpu_has_crc32 cpu_opt(LOONGARCH_CPU_CRC32)
> > #define cpu_has_complex cpu_opt(LOONGARCH_CPU_COMPLEX)
> > #define cpu_has_crypto cpu_opt(LOONGARCH_CPU_CRYPTO)
> > #define cpu_has_lvz cpu_opt(LOONGARCH_CPU_LVZ)
> > diff --git a/arch/loongarch/include/asm/cpu.h b/arch/loongarch/include/asm/cpu.h
> > index c3da91759472..ca9e2be571ec 100644
> > --- a/arch/loongarch/include/asm/cpu.h
> > +++ b/arch/loongarch/include/asm/cpu.h
> > @@ -78,25 +78,26 @@ enum cpu_type_enum {
> > #define CPU_FEATURE_FPU 3 /* CPU has FPU */
> > #define CPU_FEATURE_LSX 4 /* CPU has LSX (128-bit SIMD) */
> > #define CPU_FEATURE_LASX 5 /* CPU has LASX (256-bit SIMD) */
> > -#define CPU_FEATURE_COMPLEX 6 /* CPU has Complex instructions */
> > -#define CPU_FEATURE_CRYPTO 7 /* CPU has Crypto instructions */
> > -#define CPU_FEATURE_LVZ 8 /* CPU has Virtualization extension */
> > -#define CPU_FEATURE_LBT_X86 9 /* CPU has X86 Binary Translation */
> > -#define CPU_FEATURE_LBT_ARM 10 /* CPU has ARM Binary Translation */
> > -#define CPU_FEATURE_LBT_MIPS 11 /* CPU has MIPS Binary Translation */
> > -#define CPU_FEATURE_TLB 12 /* CPU has TLB */
> > -#define CPU_FEATURE_CSR 13 /* CPU has CSR */
> > -#define CPU_FEATURE_WATCH 14 /* CPU has watchpoint registers */
> > -#define CPU_FEATURE_VINT 15 /* CPU has vectored interrupts */
> > -#define CPU_FEATURE_CSRIPI 16 /* CPU has CSR-IPI */
> > -#define CPU_FEATURE_EXTIOI 17 /* CPU has EXT-IOI */
> > -#define CPU_FEATURE_PREFETCH 18 /* CPU has prefetch instructions */
> > -#define CPU_FEATURE_PMP 19 /* CPU has perfermance counter */
> > -#define CPU_FEATURE_SCALEFREQ 20 /* CPU supports cpufreq scaling */
> > -#define CPU_FEATURE_FLATMODE 21 /* CPU has flat mode */
> > -#define CPU_FEATURE_EIODECODE 22 /* CPU has EXTIOI interrupt pin decode mode */
> > -#define CPU_FEATURE_GUESTID 23 /* CPU has GuestID feature */
> > -#define CPU_FEATURE_HYPERVISOR 24 /* CPU has hypervisor (running in VM) */
> > +#define CPU_FEATURE_CRC32 6 /* CPU has Complex instructions */
>
> "CPU has CRC32 instructions".
>
> Also, the diff damage is real, is there any reason this must come here
> and not last? To me "aesthetics" is not enough to justify such a diff
> damage.
To keep CPU_FEATURE and elf_hwcap in the same order.
Huacai
>
> > +#define CPU_FEATURE_COMPLEX 7 /* CPU has Complex instructions */
> > +#define CPU_FEATURE_CRYPTO 8 /* CPU has Crypto instructions */
> > +#define CPU_FEATURE_LVZ 9 /* CPU has Virtualization extension */
> > +#define CPU_FEATURE_LBT_X86 10 /* CPU has X86 Binary Translation */
> > +#define CPU_FEATURE_LBT_ARM 11 /* CPU has ARM Binary Translation */
> > +#define CPU_FEATURE_LBT_MIPS 12 /* CPU has MIPS Binary Translation */
> > +#define CPU_FEATURE_TLB 13 /* CPU has TLB */
> > +#define CPU_FEATURE_CSR 14 /* CPU has CSR */
> > +#define CPU_FEATURE_WATCH 15 /* CPU has watchpoint registers */
> > +#define CPU_FEATURE_VINT 16 /* CPU has vectored interrupts */
> > +#define CPU_FEATURE_CSRIPI 17 /* CPU has CSR-IPI */
> > +#define CPU_FEATURE_EXTIOI 18 /* CPU has EXT-IOI */
> > +#define CPU_FEATURE_PREFETCH 19 /* CPU has prefetch instructions */
> > +#define CPU_FEATURE_PMP 20 /* CPU has perfermance counter */
> > +#define CPU_FEATURE_SCALEFREQ 21 /* CPU supports cpufreq scaling */
> > +#define CPU_FEATURE_FLATMODE 22 /* CPU has flat mode */
> > +#define CPU_FEATURE_EIODECODE 23 /* CPU has EXTIOI interrupt pin decode mode */
> > +#define CPU_FEATURE_GUESTID 24 /* CPU has GuestID feature */
> > +#define CPU_FEATURE_HYPERVISOR 25 /* CPU has hypervisor (running in VM) */
> >
> > #define LOONGARCH_CPU_CPUCFG BIT_ULL(CPU_FEATURE_CPUCFG)
> > #define LOONGARCH_CPU_LAM BIT_ULL(CPU_FEATURE_LAM)
> > @@ -104,6 +105,7 @@ enum cpu_type_enum {
> > #define LOONGARCH_CPU_FPU BIT_ULL(CPU_FEATURE_FPU)
> > #define LOONGARCH_CPU_LSX BIT_ULL(CPU_FEATURE_LSX)
> > #define LOONGARCH_CPU_LASX BIT_ULL(CPU_FEATURE_LASX)
> > +#define LOONGARCH_CPU_CRC32 BIT_ULL(CPU_FEATURE_CRC32)
> > #define LOONGARCH_CPU_COMPLEX BIT_ULL(CPU_FEATURE_COMPLEX)
> > #define LOONGARCH_CPU_CRYPTO BIT_ULL(CPU_FEATURE_CRYPTO)
> > #define LOONGARCH_CPU_LVZ BIT_ULL(CPU_FEATURE_LVZ)
> > diff --git a/arch/loongarch/include/asm/loongarch.h b/arch/loongarch/include/asm/loongarch.h
> > index 65b7dcdea16d..8c2969965c3c 100644
> > --- a/arch/loongarch/include/asm/loongarch.h
> > +++ b/arch/loongarch/include/asm/loongarch.h
> > @@ -117,7 +117,7 @@ static inline u32 read_cpucfg(u32 reg)
> > #define CPUCFG1_EP BIT(22)
> > #define CPUCFG1_RPLV BIT(23)
> > #define CPUCFG1_HUGEPG BIT(24)
> > -#define CPUCFG1_IOCSRBRD BIT(25)
> > +#define CPUCFG1_CRC32 BIT(25)
> > #define CPUCFG1_MSGINT BIT(26)
> >
> > #define LOONGARCH_CPUCFG2 0x2
> > diff --git a/arch/loongarch/kernel/cpu-probe.c b/arch/loongarch/kernel/cpu-probe.c
> > index 3a3fce2d7846..482643167119 100644
> > --- a/arch/loongarch/kernel/cpu-probe.c
> > +++ b/arch/loongarch/kernel/cpu-probe.c
> > @@ -94,13 +94,18 @@ static void cpu_probe_common(struct cpuinfo_loongarch *c)
> > c->options = LOONGARCH_CPU_CPUCFG | LOONGARCH_CPU_CSR |
> > LOONGARCH_CPU_TLB | LOONGARCH_CPU_VINT | LOONGARCH_CPU_WATCH;
> >
> > - elf_hwcap = HWCAP_LOONGARCH_CPUCFG | HWCAP_LOONGARCH_CRC32;
> > + elf_hwcap = HWCAP_LOONGARCH_CPUCFG;
> >
> > config = read_cpucfg(LOONGARCH_CPUCFG1);
> > if (config & CPUCFG1_UAL) {
> > c->options |= LOONGARCH_CPU_UAL;
> > elf_hwcap |= HWCAP_LOONGARCH_UAL;
> > }
> > + if (config & CPUCFG1_CRC32) {
> > + c->options |= LOONGARCH_CPU_CRC32;
> > + elf_hwcap |= HWCAP_LOONGARCH_CRC32;
> > + }
> > +
> >
> > config = read_cpucfg(LOONGARCH_CPUCFG2);
> > if (config & CPUCFG2_LAM) {
> > diff --git a/arch/loongarch/kernel/proc.c b/arch/loongarch/kernel/proc.c
> > index 5c67cc4fd56d..0d82907b5404 100644
> > --- a/arch/loongarch/kernel/proc.c
> > +++ b/arch/loongarch/kernel/proc.c
> > @@ -76,6 +76,7 @@ static int show_cpuinfo(struct seq_file *m, void *v)
> > if (cpu_has_fpu) seq_printf(m, " fpu");
> > if (cpu_has_lsx) seq_printf(m, " lsx");
> > if (cpu_has_lasx) seq_printf(m, " lasx");
> > + if (cpu_has_crc32) seq_printf(m, " crc32");
> > if (cpu_has_complex) seq_printf(m, " complex");
> > if (cpu_has_crypto) seq_printf(m, " crypto");
> > if (cpu_has_lvz) seq_printf(m, " lvz");
>
> --
> WANG "xen0n" Xuerui
>
> Linux/LoongArch mailing list: https://lore.kernel.org/loongarch/
>
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