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Date: Wed, 13 Apr 2022 13:43:26 +0800
From: Guo Ren <guoren@...nel.org>
To: Heiko Stuebner <heiko@...ech.de>
Cc: Palmer Dabbelt <palmer@...belt.com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Albert Ou <aou@...s.berkeley.edu>,
linux-riscv <linux-riscv@...ts.infradead.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Wei Fu <wefu@...hat.com>, liush <liush@...winnertech.com>,
Atish Patra <atishp@...shpatra.org>,
Anup Patel <anup@...infault.org>,
Drew Fustini <drew@...gleboard.org>,
Christoph Hellwig <hch@....de>, Arnd Bergmann <arnd@...db.de>,
Chen-Yu Tsai <wens@...e.org>,
Maxime Ripard <maxime@...no.tech>,
Greg Favor <gfavor@...tanamicro.com>,
Andrea Mondelli <andrea.mondelli@...wei.com>,
Jonathan Behrens <behrensj@....edu>,
"Xinhaoqu (Freddie)" <xinhaoqu@...wei.com>,
Nick Kossifidis <mick@....forth.gr>,
Allen Baum <allen.baum@...erantotech.com>,
Josh Scheid <jscheid@...tanamicro.com>,
Richard Trauben <rtrauben@...il.com>,
Samuel Holland <samuel@...lland.org>,
Christoph Muellner <cmuellner@...ux.com>,
Philipp Tomsich <philipp.tomsich@...ll.eu>
Subject: Re: [PATCH v9 11/12] riscv: don't use global static vars to store
alternative data
Reviewed-by: Guo Ren <guoren@...nel.org>
On Wed, Apr 13, 2022 at 11:05 AM Heiko Stuebner <heiko@...ech.de> wrote:
>
> Right now the code uses a global struct to store vendor-ids
> and another global variable to store the vendor-patch-function.
>
> There exist specific cases where we'll need to patch the kernel
> at an even earlier stage, where trying to write to a static
> variable might actually result in hangs.
>
> Also collecting the vendor-information consists of 3 sbi-ecalls
> (or csr-reads) which is pretty negligible in the context of
> booting a kernel.
>
> So rework the code to not rely on static variables and instead
> collect the vendor-information when a round of alternatives is
> to be applied.
>
> Signed-off-by: Heiko Stuebner <heiko@...ech.de>
> ---
> arch/riscv/kernel/alternative.c | 51 ++++++++++++++++-----------------
> 1 file changed, 24 insertions(+), 27 deletions(-)
>
> diff --git a/arch/riscv/kernel/alternative.c b/arch/riscv/kernel/alternative.c
> index e6c9de9f9ba6..27f722ae452b 100644
> --- a/arch/riscv/kernel/alternative.c
> +++ b/arch/riscv/kernel/alternative.c
> @@ -16,41 +16,35 @@
> #include <asm/sbi.h>
> #include <asm/csr.h>
>
> -static struct cpu_manufacturer_info_t {
> +struct cpu_manufacturer_info_t {
> unsigned long vendor_id;
> unsigned long arch_id;
> unsigned long imp_id;
> -} cpu_mfr_info;
> + void (*vendor_patch_func)(struct alt_entry *begin, struct alt_entry *end,
> + unsigned long archid, unsigned long impid,
> + unsigned int stage);
> +};
>
> -static void (*vendor_patch_func)(struct alt_entry *begin, struct alt_entry *end,
> - unsigned long archid, unsigned long impid,
> - unsigned int stage) __initdata_or_module;
> -
> -static inline void __init riscv_fill_cpu_mfr_info(void)
> +static void __init_or_module riscv_fill_cpu_mfr_info(struct cpu_manufacturer_info_t *cpu_mfr_info)
> {
> #ifdef CONFIG_RISCV_M_MODE
> - cpu_mfr_info.vendor_id = csr_read(CSR_MVENDORID);
> - cpu_mfr_info.arch_id = csr_read(CSR_MARCHID);
> - cpu_mfr_info.imp_id = csr_read(CSR_MIMPID);
> + cpu_mfr_info->vendor_id = csr_read(CSR_MVENDORID);
> + cpu_mfr_info->arch_id = csr_read(CSR_MARCHID);
> + cpu_mfr_info->imp_id = csr_read(CSR_MIMPID);
> #else
> - cpu_mfr_info.vendor_id = sbi_get_mvendorid();
> - cpu_mfr_info.arch_id = sbi_get_marchid();
> - cpu_mfr_info.imp_id = sbi_get_mimpid();
> + cpu_mfr_info->vendor_id = sbi_get_mvendorid();
> + cpu_mfr_info->arch_id = sbi_get_marchid();
> + cpu_mfr_info->imp_id = sbi_get_mimpid();
> #endif
> -}
> -
> -static void __init init_alternative(void)
> -{
> - riscv_fill_cpu_mfr_info();
>
> - switch (cpu_mfr_info.vendor_id) {
> + switch (cpu_mfr_info->vendor_id) {
> #ifdef CONFIG_ERRATA_SIFIVE
> case SIFIVE_VENDOR_ID:
> - vendor_patch_func = sifive_errata_patch_func;
> + cpu_mfr_info->vendor_patch_func = sifive_errata_patch_func;
> break;
> #endif
> default:
> - vendor_patch_func = NULL;
> + cpu_mfr_info->vendor_patch_func = NULL;
> }
> }
>
> @@ -63,14 +57,19 @@ static void __init_or_module _apply_alternatives(struct alt_entry *begin,
> struct alt_entry *end,
> unsigned int stage)
> {
> + struct cpu_manufacturer_info_t cpu_mfr_info;
> +
> + riscv_fill_cpu_mfr_info(&cpu_mfr_info);
> +
> riscv_cpufeature_patch_func(begin, end, stage);
>
> - if (!vendor_patch_func)
> + if (!cpu_mfr_info.vendor_patch_func)
> return;
>
> - vendor_patch_func(begin, end,
> - cpu_mfr_info.arch_id, cpu_mfr_info.imp_id,
> - stage);
> + cpu_mfr_info.vendor_patch_func(begin, end,
> + cpu_mfr_info.arch_id,
> + cpu_mfr_info.imp_id,
> + stage);
> }
>
> void __init apply_boot_alternatives(void)
> @@ -78,8 +77,6 @@ void __init apply_boot_alternatives(void)
> /* If called on non-boot cpu things could go wrong */
> WARN_ON(smp_processor_id() != 0);
>
> - init_alternative();
> -
> _apply_alternatives((struct alt_entry *)__alt_start,
> (struct alt_entry *)__alt_end,
> RISCV_ALTERNATIVES_BOOT);
> --
> 2.35.1
>
--
Best Regards
Guo Ren
ML: https://lore.kernel.org/linux-csky/
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