In order to be able to override CPU features at boot time, let's add a command line parser that matches options of the form "cpureg.feature=value", and store the corresponding value into the override val/mask pair. No features are currently defined, so no expected change in functionality. Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx> Acked-by: David Brazdil <dbrazdil@xxxxxxxxxx> --- arch/arm64/kernel/Makefile | 2 +- arch/arm64/kernel/head.S | 1 + arch/arm64/kernel/idreg-override.c | 130 +++++++++++++++++++++++++++++ 3 files changed, 132 insertions(+), 1 deletion(-) create mode 100644 arch/arm64/kernel/idreg-override.c diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index 86364ab6f13f..2262f0392857 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -17,7 +17,7 @@ obj-y := debug-monitors.o entry.o irq.o fpsimd.o \ return_address.o cpuinfo.o cpu_errata.o \ cpufeature.o alternative.o cacheinfo.o \ smp.o smp_spin_table.o topology.o smccc-call.o \ - syscall.o proton-pack.o + syscall.o proton-pack.o idreg-override.o targets += efi-entry.o diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index d74e5f84042e..3243e3ae9bd8 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -435,6 +435,7 @@ SYM_FUNC_START_LOCAL(__primary_switched) mov x0, x21 // pass FDT address in x0 bl early_fdt_map // Try mapping the FDT early + bl init_feature_override bl switch_to_vhe #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS) bl kasan_early_init diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c new file mode 100644 index 000000000000..2d184d6674fd --- /dev/null +++ b/arch/arm64/kernel/idreg-override.c @@ -0,0 +1,130 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Early cpufeature override framework + * + * Copyright (C) 2020 Google LLC + * Author: Marc Zyngier <maz@xxxxxxxxxx> + */ + +#include <linux/kernel.h> +#include <linux/libfdt.h> + +#include <asm/cacheflush.h> +#include <asm/setup.h> + +struct ftr_set_desc { + const char *name; + struct arm64_ftr_override *override; + struct { + const char *name; + u8 shift; + } fields[]; +}; + +static const struct ftr_set_desc * const regs[] __initdata = { +}; + +static char *cmdline_contains_option(const char *cmdline, const char *option) +{ + char *str = strstr(cmdline, option); + + if ((str == cmdline || (str > cmdline && *(str - 1) == ' '))) + return str; + + return NULL; +} + +static int __init find_field(const char *cmdline, + const struct ftr_set_desc *reg, int f, u64 *v) +{ + char buf[256], *str; + size_t len; + + snprintf(buf, ARRAY_SIZE(buf), "%s.%s=", reg->name, reg->fields[f].name); + + str = cmdline_contains_option(cmdline, buf); + if (!str) + return -1; + + str += strlen(buf); + len = strcspn(str, " "); + len = min(len, ARRAY_SIZE(buf) - 1); + strncpy(buf, str, len); + buf[len] = 0; + + return kstrtou64(buf, 0, v); +} + +static void __init match_options(const char *cmdline) +{ + int i; + + for (i = 0; i < ARRAY_SIZE(regs); i++) { + int f; + + if (!regs[i]->override) + continue; + + for (f = 0; regs[i]->fields[f].name; f++) { + u64 v; + + if (find_field(cmdline, regs[i], f, &v)) + continue; + + regs[i]->override->val |= (v & 0xf) << regs[i]->fields[f].shift; + regs[i]->override->mask |= 0xfUL << regs[i]->fields[f].shift; + } + } +} + +static __init void parse_cmdline(void) +{ + if (!IS_ENABLED(CONFIG_CMDLINE_FORCE)) { + const u8 *prop; + void *fdt; + int node; + + fdt = get_early_fdt_ptr(); + if (!fdt) + goto out; + + node = fdt_path_offset(fdt, "/chosen"); + if (node < 0) + goto out; + + prop = fdt_getprop(fdt, node, "bootargs", NULL); + if (!prop) + goto out; + + match_options(prop); + + if (!IS_ENABLED(CONFIG_CMDLINE_EXTEND)) + return; + } + +out: + match_options(CONFIG_CMDLINE); +} + +/* Keep checkers quiet */ +void init_feature_override(void); + +asmlinkage void __init init_feature_override(void) +{ + int i; + + for (i = 0; i < ARRAY_SIZE(regs); i++) { + if (regs[i]->override) { + regs[i]->override->val = 0; + regs[i]->override->mask = 0; + } + } + + parse_cmdline(); + + for (i = 0; i < ARRAY_SIZE(regs); i++) { + if (regs[i]->override) + __flush_dcache_area(regs[i]->override, + sizeof(*regs[i]->override)); + } +} -- 2.29.2 _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm