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Date: Tue, 6 Aug 2019 16:27:30 -0700 (PDT)
From: Paul Walmsley <paul.walmsley@...ive.com>
To: Atish Patra <atish.patra@....com>
cc: linux-kernel@...r.kernel.org, Albert Ou <aou@...s.berkeley.edu>,
Allison Randal <allison@...utok.net>,
Anup Patel <anup.patel@....com>,
Daniel Lezcano <daniel.lezcano@...aro.org>,
devicetree@...r.kernel.org, Enrico Weigelt <info@...ux.net>,
Gary Guo <gary@...yguo.net>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Johan Hovold <johan@...nel.org>,
linux-riscv@...ts.infradead.org,
Mark Rutland <mark.rutland@....com>,
Palmer Dabbelt <palmer@...ive.com>,
Rob Herring <robh+dt@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Yangtao Li <tiny.windzz@...il.com>
Subject: Re: [PATCH v3 3/5] RISC-V: Fix unsupported isa string info.
On Wed, 31 Jul 2019, Atish Patra wrote:
> Currently, kernel prints a info warning if any of the extensions
> from "mafdcsu" is missing in device tree. This is not entirely
> correct as Linux can boot with "f or d" extensions if kernel is
> configured accordingly. Moreover, it will continue to print the
> info string for future extensions such as hypervisor as well which
> is misleading. /proc/cpuinfo also doesn't print any other extensions
> except "mafdcsu".
>
> Make sure that info log is only printed only if kernel is configured
> to have any mandatory extensions but device tree doesn't describe it.
> All the extensions present in device tree and follow the order
> described in the RISC-V specification (except 'S') are printed via
> /proc/cpuinfo always.
>
> Signed-off-by: Atish Patra <atish.patra@....com>
I tested this patch after dropping the CONFIG_ISA_RISCV_C test (see
below). Running "cat /proc/cpuinfo" generated the following kernel
warnings:
[ 73.412626] unsupported ISA extensions "su" in device tree for cpu [0]
[ 73.418417] unsupported ISA extensions "su" in device tree for cpu [1]
[ 73.424912] unsupported ISA extensions "su" in device tree for cpu [2]
[ 73.431425] unsupported ISA extensions "su" in device tree for cpu [3]
Seems like the "su" should be dropped from mandatory_ext. What do you
think?
> ---
> arch/riscv/kernel/cpu.c | 47 ++++++++++++++++++++++++++++++++---------
> 1 file changed, 37 insertions(+), 10 deletions(-)
>
> diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
> index 7da3c6a93abd..9b1d4550fbe6 100644
> --- a/arch/riscv/kernel/cpu.c
> +++ b/arch/riscv/kernel/cpu.c
> @@ -7,6 +7,7 @@
> #include <linux/seq_file.h>
> #include <linux/of.h>
> #include <asm/smp.h>
> +#include <asm/hwcap.h>
>
> /*
> * Returns the hart ID of the given device tree node, or -ENODEV if the node
> @@ -46,11 +47,14 @@ int riscv_of_processor_hartid(struct device_node *node)
>
> #ifdef CONFIG_PROC_FS
>
> -static void print_isa(struct seq_file *f, const char *orig_isa)
> +static void print_isa(struct seq_file *f, const char *orig_isa,
> + unsigned long cpuid)
> {
> - static const char *ext = "mafdcsu";
> + static const char *mandatory_ext = "mafdcsu";
> const char *isa = orig_isa;
> const char *e;
> + char unsupported_isa[26] = {0};
> + int index = 0;
>
> /*
> * Linux doesn't support rv32e or rv128i, and we only support booting
> @@ -70,27 +74,50 @@ static void print_isa(struct seq_file *f, const char *orig_isa)
> isa += 5;
>
> /*
> - * Check the rest of the ISA string for valid extensions, printing those
> - * we find. RISC-V ISA strings define an order, so we only print the
> + * RISC-V ISA strings define an order, so we only print all the
> * extension bits when they're in order. Hide the supervisor (S)
> * extension from userspace as it's not accessible from there.
> + * Throw a warning only if any mandatory extensions are not available
> + * and kernel is configured to have that mandatory extensions.
> */
> - for (e = ext; *e != '\0'; ++e) {
> - if (isa[0] == e[0]) {
> + for (e = mandatory_ext; *e != '\0'; ++e) {
> + if (isa[0] != e[0]) {
> +#if defined(CONFIG_ISA_RISCV_C)
There's no Kconfig option by this name, and we're requiring compressed
instruction support as part of the RISC-V Linux baseline. Could you share
the rationale behind this? Looks to me like this should be dropped.
> + if (isa[0] == 'c')
> + continue;
> +#endif
> +#if defined(CONFIG_FP)
> + if ((isa[0] == 'f') || (isa[0] == 'd'))
> + continue;
> +#endif
> + unsupported_isa[index] = e[0];
> + index++;
> + }
> + /* Only write if part of isa string */
> + if (isa[0] != '\0') {
> if (isa[0] != 's')
> seq_write(f, isa, 1);
> -
> isa++;
> }
> }
> + if (isa[0] != '\0') {
> + /* Add remainging isa strings */
> + for (e = isa; *e != '\0'; ++e) {
> +#if !defined(CONFIG_VIRTUALIZATION)
> + if (e[0] != 'h')
> +#endif
> + seq_write(f, e, 1);
> + }
> + }
> seq_puts(f, "\n");
>
> /*
> * If we were given an unsupported ISA in the device tree then print
> * a bit of info describing what went wrong.
> */
> - if (isa[0] != '\0')
> - pr_info("unsupported ISA \"%s\" in device tree\n", orig_isa);
> + if (unsupported_isa[0])
> + pr_info("unsupported ISA extensions \"%s\" in device tree for cpu [%ld]\n",
> + unsupported_isa, cpuid);
> }
>
> static void print_mmu(struct seq_file *f, const char *mmu_type)
> @@ -134,7 +161,7 @@ static int c_show(struct seq_file *m, void *v)
> seq_printf(m, "processor\t: %lu\n", cpu_id);
> seq_printf(m, "hart\t\t: %lu\n", cpuid_to_hartid_map(cpu_id));
> if (!of_property_read_string(node, "riscv,isa", &isa))
> - print_isa(m, isa);
> + print_isa(m, isa, cpu_id);
> if (!of_property_read_string(node, "mmu-type", &mmu))
> print_mmu(m, mmu);
> if (!of_property_read_string(node, "compatible", &compat)
> --
> 2.21.0
>
>
- Paul
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