Re: [PATCH v4 09/21] arm64: cpufeature: Add global feature override facility
From: Catalin Marinas <catalin.marinas@arm.com>
Date: 2021-01-22 19:35:57
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On Mon, Jan 18, 2021 at 09:45:21AM +0000, Marc Zyngier wrote:
quoted hunk ↗ jump to hunk
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index 9a555809b89c..465d2cb63bfc 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h@@ -75,6 +75,8 @@ struct arm64_ftr_reg { u64 sys_val; u64 user_val; const struct arm64_ftr_bits *ftr_bits; + u64 *override_val; + u64 *override_mask; }; extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0;diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index e99eddec0a46..aaa075c6f029 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c@@ -544,13 +544,17 @@ 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, v, m) { \ + .sys_id = id, \ + .reg = &(struct arm64_ftr_reg){ \ + .name = #id, \ + .ftr_bits = &((table)[0]), \ + .override_val = v, \ + .override_mask = m, \ }} +#define ARM64_FTR_REG(id, table) ARM64_FTR_REG_OVERRIDE(id, table, NULL, NULL) + static const struct __ftr_reg_entry { u32 sys_id; struct arm64_ftr_reg *reg;@@ -760,6 +764,7 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new) u64 strict_mask = ~0x0ULL; u64 user_mask = 0; u64 valid_mask = 0; + u64 override_val = 0, override_mask = 0; const struct arm64_ftr_bits *ftrp; struct arm64_ftr_reg *reg = get_arm64_ftr_reg(sys_reg);@@ -767,9 +772,38 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new) if (!reg) return; + if (reg->override_mask && reg->override_val) { + override_mask = *reg->override_mask; + override_val = *reg->override_val; + } + 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, override_val); + + if ((ftr_mask & 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;
Do we need such clearing here? I don't think that's ever called again for this feature/reg.
+ 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);I wonder whether we could call, after init_cpu_ftr_reg(), a new function similar to update_cpu_ftr_reg() that takes a mask and value and leave init_cpu_ftr_reg() unchanged. The only advantage would be if we can get rid of the reg->override* fields. Anyway, I need to read the rest of the series to see whether it's possible. Otherwise this patch looks fine. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel