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From: Marc Zyngier <maz@kernel.org>
To: linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org
Cc: Prasad Sodagudi <psodagud@codeaurora.org>,
	Srinivas Ramana <sramana@codeaurora.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Ajay Patil <pajay@qti.qualcomm.com>,
	kernel-team@android.com, Will Deacon <will@kernel.org>,
	Ard Biesheuvel <ardb@kernel.org>
Subject: [PATCH v5 09/21] arm64: cpufeature: Add global feature override facility
Date: Mon, 25 Jan 2021 10:50:07 +0000	[thread overview]
Message-ID: <20210125105019.2946057-10-maz@kernel.org> (raw)
In-Reply-To: <20210125105019.2946057-1-maz@kernel.org>

Add a facility to globally override a feature, no matter what
the HW says. Yes, this sounds dangerous, but we do respect the
"safe" value for a given feature. This doesn't mean the user
doesn't need to know what they are doing.

Nothing uses this yet, so we are pretty safe. For now.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Acked-by: David Brazdil <dbrazdil@google.com>
---
 arch/arm64/include/asm/cpufeature.h |  6 +++++
 arch/arm64/kernel/cpufeature.c      | 42 ++++++++++++++++++++++++-----
 2 files changed, 42 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 9a555809b89c..fe469389068e 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -63,6 +63,11 @@ struct arm64_ftr_bits {
 	s64		safe_val; /* safe value for FTR_EXACT features */
 };
 
+struct arm64_ftr_override {
+	u64		val;
+	u64		mask;
+};
+
 /*
  * @arm64_ftr_reg - Feature register
  * @strict_mask		Bits which should match across all CPUs for sanity.
@@ -74,6 +79,7 @@ struct arm64_ftr_reg {
 	u64				user_mask;
 	u64				sys_val;
 	u64				user_val;
+	struct arm64_ftr_override 	*override;
 	const struct arm64_ftr_bits	*ftr_bits;
 };
 
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index e99eddec0a46..cb58c7c991ef 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -352,9 +352,12 @@ static const struct arm64_ftr_bits ftr_ctr[] = {
 	ARM64_FTR_END,
 };
 
+static struct arm64_ftr_override no_override = { };
+
 struct arm64_ftr_reg arm64_ftr_reg_ctrel0 = {
 	.name		= "SYS_CTR_EL0",
-	.ftr_bits	= ftr_ctr
+	.ftr_bits	= ftr_ctr,
+	.override	= &no_override,
 };
 
 static const struct arm64_ftr_bits ftr_id_mmfr0[] = {
@@ -544,13 +547,16 @@ static const struct arm64_ftr_bits ftr_raz[] = {
 	ARM64_FTR_END,
 };
 
-#define ARM64_FTR_REG(id, table) {		\
-	.sys_id = id,				\
-	.reg = 	&(struct arm64_ftr_reg){	\
-		.name = #id,			\
-		.ftr_bits = &((table)[0]),	\
+#define ARM64_FTR_REG_OVERRIDE(id, table, ovr) {		\
+		.sys_id = id,					\
+		.reg = 	&(struct arm64_ftr_reg){		\
+			.name = #id,				\
+			.override = (ovr),			\
+			.ftr_bits = &((table)[0]),		\
 	}}
 
+#define ARM64_FTR_REG(id, table) ARM64_FTR_REG_OVERRIDE(id, table, &no_override)
+
 static const struct __ftr_reg_entry {
 	u32			sys_id;
 	struct arm64_ftr_reg 	*reg;
@@ -770,6 +776,30 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new)
 	for (ftrp = reg->ftr_bits; ftrp->width; ftrp++) {
 		u64 ftr_mask = arm64_ftr_mask(ftrp);
 		s64 ftr_new = arm64_ftr_value(ftrp, new);
+		s64 ftr_ovr = arm64_ftr_value(ftrp, reg->override->val);
+
+		if ((ftr_mask & reg->override->mask) == ftr_mask) {
+			s64 tmp = arm64_ftr_safe_value(ftrp, ftr_ovr, ftr_new);
+			char *str = NULL;
+
+			if (ftr_ovr != tmp) {
+				/* Unsafe, remove the override */
+				reg->override->mask &= ~ftr_mask;
+				reg->override->val &= ~ftr_mask;
+				tmp = ftr_ovr;
+				str = "ignoring override";
+			} else if (ftr_new != tmp) {
+				/* Override was valid */
+				ftr_new = tmp;
+				str = "forced";
+			}
+
+			if (str)
+				pr_warn("%s[%d:%d]: %s to %llx\n",
+					reg->name,
+					ftrp->shift + ftrp->width - 1,
+					ftrp->shift, str, tmp);
+		}
 
 		val = arm64_ftr_set_value(ftrp, val, ftr_new);
 
-- 
2.29.2

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  parent reply	other threads:[~2021-01-25 10:50 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-25 10:49 [PATCH v5 00/21] arm64: Early CPU feature override, and applications to VHE, BTI and PAuth Marc Zyngier
2021-01-25 10:49 ` [PATCH v5 01/21] arm64: Fix labels in el2_setup macros Marc Zyngier
2021-01-25 10:50 ` [PATCH v5 02/21] arm64: Fix outdated TCR setup comment Marc Zyngier
2021-01-25 10:50 ` [PATCH v5 03/21] arm64: Turn the MMU-on sequence into a macro Marc Zyngier
2021-01-25 10:50 ` [PATCH v5 04/21] arm64: Provide an 'upgrade to VHE' stub hypercall Marc Zyngier
2021-01-25 12:13   ` Catalin Marinas
2021-01-25 10:50 ` [PATCH v5 05/21] arm64: Initialise as nVHE before switching to VHE Marc Zyngier
2021-01-25 12:13   ` Catalin Marinas
2021-01-25 10:50 ` [PATCH v5 06/21] arm64: Move VHE-specific SPE setup to mutate_to_vhe() Marc Zyngier
2021-01-25 12:14   ` Catalin Marinas
2021-01-25 10:50 ` [PATCH v5 07/21] arm64: Simplify init_el2_state to be non-VHE only Marc Zyngier
2021-01-25 12:14   ` Catalin Marinas
2021-01-25 10:50 ` [PATCH v5 08/21] arm64: Move SCTLR_EL1 initialisation to EL-agnostic code Marc Zyngier
2021-01-25 10:50 ` Marc Zyngier [this message]
2021-01-25 12:15   ` [PATCH v5 09/21] arm64: cpufeature: Add global feature override facility Catalin Marinas
2021-01-25 10:50 ` [PATCH v5 10/21] arm64: cpufeature: Use IDreg override in __read_sysreg_by_encoding() Marc Zyngier
2021-01-25 12:19   ` Catalin Marinas
2021-01-25 10:50 ` [PATCH v5 11/21] arm64: Extract early FDT mapping from kaslr_early_init() Marc Zyngier
2021-01-25 10:50 ` [PATCH v5 12/21] arm64: cpufeature: Add an early command-line cpufeature override facility Marc Zyngier
2021-01-25 18:37   ` Catalin Marinas
2021-01-25 10:50 ` [PATCH v5 13/21] arm64: Allow ID_AA64MMFR1_EL1.VH to be overridden from the command line Marc Zyngier
2021-01-25 13:15   ` Suzuki K Poulose
2021-01-25 13:55     ` Marc Zyngier
2021-01-25 18:37   ` Catalin Marinas
2021-01-25 10:50 ` [PATCH v5 14/21] arm64: Honor VHE being disabled from the command-line Marc Zyngier
2021-01-25 18:38   ` Catalin Marinas
2021-01-25 10:50 ` [PATCH v5 15/21] arm64: Add an aliasing facility for the idreg override Marc Zyngier
2021-01-25 10:50 ` [PATCH v5 16/21] arm64: Make kvm-arm.mode={nvhe, protected} an alias of id_aa64mmfr1.vh=0 Marc Zyngier
2021-01-25 10:50 ` [PATCH v5 17/21] KVM: arm64: Document HVC_VHE_RESTART stub hypercall Marc Zyngier
2021-01-25 10:50 ` [PATCH v5 18/21] arm64: Move "nokaslr" over to the early cpufeature infrastructure Marc Zyngier
2021-01-25 12:54   ` Ard Biesheuvel
2021-01-25 13:54     ` Marc Zyngier
2021-01-25 14:19       ` Ard Biesheuvel
2021-01-25 14:28         ` Marc Zyngier
2021-01-25 15:00           ` Ard Biesheuvel
2021-01-25 10:50 ` [PATCH v5 19/21] arm64: cpufeatures: Allow disabling of BTI from the command-line Marc Zyngier
2021-01-25 10:50 ` [PATCH v5 20/21] arm64: Defer enabling pointer authentication on boot core Marc Zyngier
2021-01-25 10:50 ` [PATCH v5 21/21] arm64: cpufeatures: Allow disabling of Pointer Auth from the command-line Marc Zyngier

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