Unverified Commit 1745cfaf authored by Heiko Stuebner's avatar Heiko Stuebner Committed by Palmer Dabbelt
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riscv: don't use global static vars to store alternative data 



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: default avatarHeiko Stuebner <heiko@sntech.de>
Reviewed-by: default avatarGuo Ren <guoren@kernel.org>
Reviewed-by: default avatarPhilipp Tomsich <philipp.tomsich@vrull.eu>
Link: https://lore.kernel.org/r/20220511192921.2223629-12-heiko@sntech.de


Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent e1026505

arch/riscv/kernel/alternative.c

+24 −27
Original line number Diff line number Diff line
@@ -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;



static void (*vendor_patch_func)(struct alt_entry *begin, struct alt_entry *end,

	void (*vendor_patch_func)(struct alt_entry *begin, struct alt_entry *end,

				  unsigned long archid, unsigned long impid,

				 unsigned int stage) __initdata_or_module;

				  unsigned int stage);

};



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;

	}

}
@@ -63,13 +57,18 @@ 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,

	cpu_mfr_info.vendor_patch_func(begin, end,

				   cpu_mfr_info.arch_id,

				   cpu_mfr_info.imp_id,

				   stage);

}
@@ -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);