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 <[email protected]>
---
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
On Wed, 13 Apr 2022 at 05:05, Heiko Stuebner <[email protected]> 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 <[email protected]>
Reviewed-by: Philipp Tomsich <[email protected]>
Reviewed-by: Guo Ren <[email protected]>
On Wed, Apr 13, 2022 at 11:05 AM Heiko Stuebner <[email protected]> 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 <[email protected]>
> ---
> 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/