| Message ID | 20210104135011.2063104-12-maz@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: Early CPU feature override, and an application to VHE | expand |
On Mon, Jan 4, 2021 at 8:20 AM Marc Zyngier <maz@kernel.org> wrote: > > 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 > functionnality. Typo: functionnality -> functionality > > Signed-off-by: Marc Zyngier <maz@kernel.org> > --- > arch/arm64/kernel/Makefile | 2 +- > arch/arm64/kernel/head.S | 1 + > arch/arm64/kernel/idreg-override.c | 119 +++++++++++++++++++++++++++++ > 3 files changed, 121 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..b3c4dd04f74b 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_shadow_regs > 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..392f93b67103 > --- /dev/null > +++ b/arch/arm64/kernel/idreg-override.c > @@ -0,0 +1,119 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Early cpufeature override framework > + * > + * Copyright (C) 2020 Google LLC > + * Author: Marc Zyngier <maz@kernel.org> > + */ > + > +#include <linux/kernel.h> > +#include <linux/libfdt.h> > + > +#include <asm/cacheflush.h> > +#include <asm/setup.h> > + > +struct reg_desc { > + const char * const name; > + u64 * const val; > + u64 * const mask; > + struct { > + const char * const name; > + u8 shift; > + } fields[]; > +}; > + > +static const struct reg_desc * const regs[] __initdata = { > +}; > + > +static int __init find_field(const char *cmdline, const struct reg_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 = strstr(cmdline, buf); > + if (!(str == cmdline || (str > cmdline && *(str - 1) == ' '))) > + 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]->val || !regs[i]->mask) > + continue; > + > + for (f = 0; regs[i]->fields[f].name; f++) { > + u64 v; > + > + if (find_field(cmdline, regs[i], f, &v)) > + continue; > + > + *regs[i]->val |= (v & 0xf) << regs[i]->fields[f].shift; > + *regs[i]->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); > +} > + > +void __init init_shadow_regs(void) > +{ > + int i; > + > + for (i = 0; i < ARRAY_SIZE(regs); i++) { > + if (regs[i]->val) > + *regs[i]->val = 0; > + if (regs[i]->mask) > + *regs[i]->mask = 0; > + } > + > + parse_cmdline(); > + > + for (i = 0; i < ARRAY_SIZE(regs); i++) { > + if (regs[i]->val) > + __flush_dcache_area(regs[i]->val, sizeof(*regs[i]->val)); > + if (regs[i]->mask) > + __flush_dcache_area(regs[i]->mask, sizeof(*regs[i]->mask)); > + } Could you shed some light on the usage of __flush_dcache_area here? Thanks. > +} > -- > 2.29.2 > > _______________________________________________ > kvmarm mailing list > kvmarm@lists.cs.columbia.edu > https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
On 2021-01-06 02:16, Jing Zhang wrote: > On Mon, Jan 4, 2021 at 8:20 AM Marc Zyngier <maz@kernel.org> wrote: [...] >> +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); >> +} >> + >> +void __init init_shadow_regs(void) >> +{ >> + int i; >> + >> + for (i = 0; i < ARRAY_SIZE(regs); i++) { >> + if (regs[i]->val) >> + *regs[i]->val = 0; >> + if (regs[i]->mask) >> + *regs[i]->mask = 0; >> + } >> + >> + parse_cmdline(); >> + >> + for (i = 0; i < ARRAY_SIZE(regs); i++) { >> + if (regs[i]->val) >> + __flush_dcache_area(regs[i]->val, >> sizeof(*regs[i]->val)); >> + if (regs[i]->mask) >> + __flush_dcache_area(regs[i]->mask, >> sizeof(*regs[i]->mask)); >> + } > Could you shed some light on the usage of __flush_dcache_area here? > Thanks. Some of this data gets used by secondary CPUs when they have their MMU off. If we don't clean to the PoC, they will miss the updates and things will randomly fail. M.
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..b3c4dd04f74b 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_shadow_regs 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..392f93b67103 --- /dev/null +++ b/arch/arm64/kernel/idreg-override.c @@ -0,0 +1,119 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Early cpufeature override framework + * + * Copyright (C) 2020 Google LLC + * Author: Marc Zyngier <maz@kernel.org> + */ + +#include <linux/kernel.h> +#include <linux/libfdt.h> + +#include <asm/cacheflush.h> +#include <asm/setup.h> + +struct reg_desc { + const char * const name; + u64 * const val; + u64 * const mask; + struct { + const char * const name; + u8 shift; + } fields[]; +}; + +static const struct reg_desc * const regs[] __initdata = { +}; + +static int __init find_field(const char *cmdline, const struct reg_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 = strstr(cmdline, buf); + if (!(str == cmdline || (str > cmdline && *(str - 1) == ' '))) + 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]->val || !regs[i]->mask) + continue; + + for (f = 0; regs[i]->fields[f].name; f++) { + u64 v; + + if (find_field(cmdline, regs[i], f, &v)) + continue; + + *regs[i]->val |= (v & 0xf) << regs[i]->fields[f].shift; + *regs[i]->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); +} + +void __init init_shadow_regs(void) +{ + int i; + + for (i = 0; i < ARRAY_SIZE(regs); i++) { + if (regs[i]->val) + *regs[i]->val = 0; + if (regs[i]->mask) + *regs[i]->mask = 0; + } + + parse_cmdline(); + + for (i = 0; i < ARRAY_SIZE(regs); i++) { + if (regs[i]->val) + __flush_dcache_area(regs[i]->val, sizeof(*regs[i]->val)); + if (regs[i]->mask) + __flush_dcache_area(regs[i]->mask, sizeof(*regs[i]->mask)); + } +}
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 functionnality. Signed-off-by: Marc Zyngier <maz@kernel.org> --- arch/arm64/kernel/Makefile | 2 +- arch/arm64/kernel/head.S | 1 + arch/arm64/kernel/idreg-override.c | 119 +++++++++++++++++++++++++++++ 3 files changed, 121 insertions(+), 1 deletion(-) create mode 100644 arch/arm64/kernel/idreg-override.c