From: Marc Zyngier <maz@kernel.org>
To: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu
Cc: kernel-team@android.com,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, Ard Biesheuvel <ardb@kernel.org>
Subject: [PATCH 11/17] arm64: cpufeature: Add an early command-line cpufeature override facility
Date: Mon, 28 Dec 2020 10:49:52 +0000 [thread overview]
Message-ID: <20201228104958.1848833-12-maz@kernel.org> (raw)
In-Reply-To: <20201228104958.1848833-1-maz@kernel.org>
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 | 112 +++++++++++++++++++++++++++++
3 files changed, 114 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..98fc664c2504
--- /dev/null
+++ b/arch/arm64/kernel/idreg-override.c
@@ -0,0 +1,112 @@
+// 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;
+
+ 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++) {
+ *regs[i]->val = 0;
+ *regs[i]->mask = 0;
+ }
+
+ parse_cmdline();
+
+ for (i = 0; i < ARRAY_SIZE(regs); i++) {
+ __flush_dcache_area(regs[i]->val, sizeof(*regs[i]->val));
+ __flush_dcache_area(regs[i]->mask, sizeof(*regs[i]->mask));
+ }
+}
--
2.29.2
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next prev parent reply other threads:[~2020-12-28 11:20 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-28 10:49 [PATCH 00/17] arm64: Early CPU feature override, and an application to VHE Marc Zyngier
2020-12-28 10:49 ` [PATCH 01/17] arm64: Fix labels in el2_setup macros Marc Zyngier
2020-12-28 10:49 ` [PATCH 02/17] arm64: Fix outdated TCR setup comment Marc Zyngier
2020-12-28 10:49 ` [PATCH 03/17] arm64: Turn the MMU-on sequence into a macro Marc Zyngier
2020-12-28 10:49 ` [PATCH 04/17] arm64: Provide an 'upgrade to VHE' stub hypercall Marc Zyngier
2021-01-04 23:39 ` Jing Zhang
2021-01-05 8:24 ` Marc Zyngier
2020-12-28 10:49 ` [PATCH 05/17] arm64: Initialise as nVHE before switching to VHE Marc Zyngier
2020-12-28 10:49 ` [PATCH 06/17] arm64: Move VHE-specific SPE setup to mutate_to_vhe() Marc Zyngier
2020-12-28 10:49 ` [PATCH 07/17] arm64: Simplify init_el2_state to be non-VHE only Marc Zyngier
2020-12-28 10:49 ` [PATCH 08/17] arm64: Move SCTLR_EL1 initialisation to EL-agnostic code Marc Zyngier
2020-12-28 10:49 ` [PATCH 09/17] arm64: cpufeature: Add global feature override facility Marc Zyngier
2020-12-28 10:49 ` [PATCH 10/17] arm64: Extract early FDT mapping from kaslr_early_init() Marc Zyngier
2020-12-28 10:49 ` Marc Zyngier [this message]
2020-12-28 10:49 ` [PATCH 12/17] arm64: Allow ID_AA64MMFR1_EL1.VH to be overridden from the command line Marc Zyngier
2020-12-28 10:49 ` [PATCH 13/17] arm64: Honor VHE being disabled from the command-line Marc Zyngier
2020-12-28 10:49 ` [PATCH 14/17] arm64: Add an aliasing facility for the idreg override Marc Zyngier
2020-12-28 10:49 ` [PATCH 15/17] arm64: Make kvm-arm.mode={nvhe, protected} an alias of id_aa64mmfr1.vh=0 Marc Zyngier
2020-12-28 10:49 ` [PATCH 16/17] KVM: arm64: Document HVC_VHE_RESTART stub hypercall Marc Zyngier
2020-12-28 10:49 ` [PATCH 17/17] arm64: Move "nokaslr" over to the early cpufeature infrastructure Marc Zyngier
2020-12-29 19:27 ` [PATCH 00/17] arm64: Early CPU feature override, and an application to VHE Marc Zyngier
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