RISC-V: Some Svpbmt fixes and cleanups

Some additionals comments and notes from autobuilders received after the
series got applied, warranted some changes.

* 'riscv-svpbmt' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/palmer/linux:
  riscv: remove usage of function-pointers from cpufeatures and t-head errata
  riscv: make patch-function pointer more generic in cpu_manufacturer_info struct
  riscv: Improve description for RISCV_ISA_SVPBMT Kconfig symbol
  riscv: drop cpufeature_apply_feature tracking variable
  riscv: fix dependency for t-head errata

Author: palmer-dabbelt

arch/riscv/Kconfig

@@ -364,8 +364,13 @@ config RISCV_ISA_SVPBMT
 	select RISCV_ALTERNATIVE
 	default y
 	help
-	   Adds support to dynamically detect the presence of the SVPBMT extension
-	   (Supervisor-mode: page-based memory types) and enable its usage.
+	   Adds support to dynamically detect the presence of the SVPBMT
+	   ISA-extension (Supervisor-mode: page-based memory types) and
+	   enable its usage.
+
+	   The memory type for a page contains a combination of attributes
+	   that indicate the cacheability, idempotency, and ordering
+	   properties for access to that page.
 
 	   The SVPBMT extension is only available on 64Bit cpus.
 

arch/riscv/Kconfig.erratas

@@ -35,6 +35,7 @@ config ERRATA_SIFIVE_CIP_1200
 
 config ERRATA_THEAD
 	bool "T-HEAD errata"
+	depends on !XIP_KERNEL
 	select RISCV_ALTERNATIVE
 	help
 	  All T-HEAD errata Kconfig depend on this Kconfig. Disabling

arch/riscv/errata/thead/errata.c

@@ -14,40 +14,26 @@
 #include <asm/patch.h>
 #include <asm/vendorid_list.h>
 
-struct errata_info {
-	char name[ERRATA_STRING_LENGTH_MAX];
-	bool (*check_func)(unsigned long arch_id, unsigned long impid);
-	unsigned int stage;
-};
-
-static bool errata_mt_check_func(unsigned long  arch_id, unsigned long impid)
+static bool errata_probe_pbmt(unsigned int stage,
+			      unsigned long arch_id, unsigned long impid)
 {
 	if (arch_id != 0 || impid != 0)
 		return false;
-	return true;
-}
 
-static const struct errata_info errata_list[ERRATA_THEAD_NUMBER] = {
-	{
-		.name = "memory-types",
-		.stage = RISCV_ALTERNATIVES_EARLY_BOOT,
-		.check_func = errata_mt_check_func
-	},
-};
+	if (stage == RISCV_ALTERNATIVES_EARLY_BOOT ||
+	    stage == RISCV_ALTERNATIVES_MODULE)
+		return true;
+
+	return false;
+}
 
-static u32 thead_errata_probe(unsigned int stage, unsigned long archid, unsigned long impid)
+static u32 thead_errata_probe(unsigned int stage,
+			      unsigned long archid, unsigned long impid)
 {
-	const struct errata_info *info;
 	u32 cpu_req_errata = 0;
-	int idx;
-
-	for (idx = 0; idx < ERRATA_THEAD_NUMBER; idx++) {
-		info = &errata_list[idx];
 
-		if ((stage == RISCV_ALTERNATIVES_MODULE ||
-		     info->stage == stage) && info->check_func(archid, impid))
-			cpu_req_errata |= (1U << idx);
-	}
+	if (errata_probe_pbmt(stage, archid, impid))
+		cpu_req_errata |= (1U << ERRATA_THEAD_PBMT);
 
 	return cpu_req_errata;
 }

arch/riscv/kernel/alternative.c

@@ -20,7 +20,7 @@ struct cpu_manufacturer_info_t {
 	unsigned long vendor_id;
 	unsigned long arch_id;
 	unsigned long imp_id;
-	void (*vendor_patch_func)(struct alt_entry *begin, struct alt_entry *end,
+	void (*patch_func)(struct alt_entry *begin, struct alt_entry *end,
 				  unsigned long archid, unsigned long impid,
 				  unsigned int stage);
 };
@@ -40,16 +40,16 @@ static void __init_or_module riscv_fill_cpu_mfr_info(struct cpu_manufacturer_inf
 	switch (cpu_mfr_info->vendor_id) {
 #ifdef CONFIG_ERRATA_SIFIVE
 	case SIFIVE_VENDOR_ID:
-		cpu_mfr_info->vendor_patch_func = sifive_errata_patch_func;
+		cpu_mfr_info->patch_func = sifive_errata_patch_func;
 		break;
 #endif
 #ifdef CONFIG_ERRATA_THEAD
 	case THEAD_VENDOR_ID:
-		cpu_mfr_info->vendor_patch_func = thead_errata_patch_func;
+		cpu_mfr_info->patch_func = thead_errata_patch_func;
 		break;
 #endif
 	default:
-		cpu_mfr_info->vendor_patch_func = NULL;
+		cpu_mfr_info->patch_func = NULL;
 	}
 }
 
@@ -68,13 +68,13 @@ static void __init_or_module _apply_alternatives(struct alt_entry *begin,
 
 	riscv_cpufeature_patch_func(begin, end, stage);
 
-	if (!cpu_mfr_info.vendor_patch_func)
+	if (!cpu_mfr_info.patch_func)
 		return;
 
-	cpu_mfr_info.vendor_patch_func(begin, end,
-				   cpu_mfr_info.arch_id,
-				   cpu_mfr_info.imp_id,
-				   stage);
+	cpu_mfr_info.patch_func(begin, end,
+				cpu_mfr_info.arch_id,
+				cpu_mfr_info.imp_id,
+				stage);
 }
 
 void __init apply_boot_alternatives(void)

arch/riscv/kernel/cpufeature.c

@@ -245,12 +245,7 @@ void __init riscv_fill_hwcap(void)
 }
 
 #ifdef CONFIG_RISCV_ALTERNATIVE
-struct cpufeature_info {
-	char name[ERRATA_STRING_LENGTH_MAX];
-	bool (*check_func)(unsigned int stage);
-};
-
-static bool __init_or_module cpufeature_svpbmt_check_func(unsigned int stage)
+static bool __init_or_module cpufeature_probe_svpbmt(unsigned int stage)
 {
 #ifdef CONFIG_RISCV_ISA_SVPBMT
 	switch (stage) {
@@ -264,26 +259,19 @@ static bool __init_or_module cpufeature_svpbmt_check_func(unsigned int stage)
 	return false;
 }
 
-static const struct cpufeature_info __initdata_or_module
-cpufeature_list[CPUFEATURE_NUMBER] = {
-	{
-		.name = "svpbmt",
-		.check_func = cpufeature_svpbmt_check_func
-	},
-};
-
+/*
+ * Probe presence of individual extensions.
+ *
+ * This code may also be executed before kernel relocation, so we cannot use
+ * addresses generated by the address-of operator as they won't be valid in
+ * this context.
+ */
 static u32 __init_or_module cpufeature_probe(unsigned int stage)
 {
-	const struct cpufeature_info *info;
 	u32 cpu_req_feature = 0;
-	int idx;
-
-	for (idx = 0; idx < CPUFEATURE_NUMBER; idx++) {
-		info = &cpufeature_list[idx];
 
-		if (info->check_func(stage))
-			cpu_req_feature |= (1U << idx);
-	}
+	if (cpufeature_probe_svpbmt(stage))
+		cpu_req_feature |= (1U << CPUFEATURE_SVPBMT);
 
 	return cpu_req_feature;
 }
@@ -293,7 +281,6 @@ void __init_or_module riscv_cpufeature_patch_func(struct alt_entry *begin,
 						  unsigned int stage)
 {
 	u32 cpu_req_feature = cpufeature_probe(stage);
-	u32 cpu_apply_feature = 0;
 	struct alt_entry *alt;
 	u32 tmp;
 
@@ -307,10 +294,8 @@ void __init_or_module riscv_cpufeature_patch_func(struct alt_entry *begin,
 		}
 
 		tmp = (1U << alt->errata_id);
-		if (cpu_req_feature & tmp) {
+		if (cpu_req_feature & tmp)
 			patch_text_nosync(alt->old_ptr, alt->alt_ptr, alt->alt_len);
-			cpu_apply_feature |= tmp;
-		}
 	}
 }
 #endif