linux-kernel - [PATCH v2 08/10] MIPS: Avoid unnecessary reservation of exception space

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Message-Id: <20231027221106.405666-9-jiaxun.yang@flygoat.com>
Date:   Fri, 27 Oct 2023 23:11:04 +0100
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     linux-mips@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, tsbogend@...ha.franken.de,
        gregory.clement@...tlin.com, vladimir.kondratiev@...el.com,
        Jiaxun Yang <jiaxun.yang@...goat.com>
Subject: [PATCH v2 08/10] MIPS: Avoid unnecessary reservation of exception space

Nowadays we allocate exception base from memblock for r2_r6,
so we don't need to reverse exception space at the start of
the memory for r2_r6 processors.

For older processors the reservation is moved to traps_init
where we have knowledge of exact size we need. We also add
a sanity check to detect possible overlap with kernel.

Signed-off-by: Jiaxun Yang <jiaxun.yang@...goat.com>
---
 arch/mips/include/asm/traps.h    |  1 -
 arch/mips/kernel/cpu-probe.c     |  5 -----
 arch/mips/kernel/cpu-r3k-probe.c |  2 --
 arch/mips/kernel/traps.c         | 12 +++++++-----
 4 files changed, 7 insertions(+), 13 deletions(-)

diff --git a/arch/mips/include/asm/traps.h b/arch/mips/include/asm/traps.h
index 15cde638b407..d3dddd1c083a 100644
--- a/arch/mips/include/asm/traps.h
+++ b/arch/mips/include/asm/traps.h
@@ -24,7 +24,6 @@ extern void (*board_ebase_setup)(void);
 extern void (*board_cache_error_setup)(void);
 
 extern int register_nmi_notifier(struct notifier_block *nb);
-extern void reserve_exception_space(phys_addr_t addr, unsigned long size);
 extern char except_vec_nmi[];
 
 #define VECTORSPACING 0x100	/* for EI/VI mode */
diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
index b406d8bfb15a..54e8b0fd4a2a 100644
--- a/arch/mips/kernel/cpu-probe.c
+++ b/arch/mips/kernel/cpu-probe.c
@@ -1570,7 +1570,6 @@ static inline void cpu_probe_broadcom(struct cpuinfo_mips *c, unsigned int cpu)
 		c->cputype = CPU_BMIPS3300;
 		__cpu_name[cpu] = "Broadcom BMIPS3300";
 		set_elf_platform(cpu, "bmips3300");
-		reserve_exception_space(0x400, VECTORSPACING * 64);
 		break;
 	case PRID_IMP_BMIPS43XX: {
 		int rev = c->processor_id & PRID_REV_MASK;
@@ -1581,7 +1580,6 @@ static inline void cpu_probe_broadcom(struct cpuinfo_mips *c, unsigned int cpu)
 			__cpu_name[cpu] = "Broadcom BMIPS4380";
 			set_elf_platform(cpu, "bmips4380");
 			c->options |= MIPS_CPU_RIXI;
-			reserve_exception_space(0x400, VECTORSPACING * 64);
 		} else {
 			c->cputype = CPU_BMIPS4350;
 			__cpu_name[cpu] = "Broadcom BMIPS4350";
@@ -1598,7 +1596,6 @@ static inline void cpu_probe_broadcom(struct cpuinfo_mips *c, unsigned int cpu)
 			__cpu_name[cpu] = "Broadcom BMIPS5000";
 		set_elf_platform(cpu, "bmips5000");
 		c->options |= MIPS_CPU_ULRI | MIPS_CPU_RIXI;
-		reserve_exception_space(0x1000, VECTORSPACING * 64);
 		break;
 	}
 }
@@ -1996,8 +1993,6 @@ void cpu_probe(void)
 	if (cpu == 0)
 		__ua_limit = ~((1ull << cpu_vmbits) - 1);
 #endif
-
-	reserve_exception_space(0, 0x1000);
 }
 
 void cpu_report(void)
diff --git a/arch/mips/kernel/cpu-r3k-probe.c b/arch/mips/kernel/cpu-r3k-probe.c
index be93469c0e0e..05410b743e57 100644
--- a/arch/mips/kernel/cpu-r3k-probe.c
+++ b/arch/mips/kernel/cpu-r3k-probe.c
@@ -137,8 +137,6 @@ void cpu_probe(void)
 		cpu_set_fpu_opts(c);
 	else
 		cpu_set_nofpu_opts(c);
-
-	reserve_exception_space(0, 0x400);
 }
 
 void cpu_report(void)
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 651c9ec6265a..b6e94654f621 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -2007,10 +2007,6 @@ unsigned long exception_handlers[32];
 static unsigned long vi_vecbase;
 unsigned long vi_handlers[64];
 
-void reserve_exception_space(phys_addr_t addr, unsigned long size)
-{
-	memblock_reserve(addr, size);
-}
 
 void __init *set_except_vector(int n, void *addr)
 {
@@ -2394,7 +2390,13 @@ void __init trap_init(void)
 	}
 
 	if (!cpu_has_mips_r2_r6) {
-		ebase = CAC_BASE;
+		ebase_pa = 0x0;
+		ebase = CKSEG0ADDR(ebase_pa);
+
+		if (__pa_symbol(_stext) < (ebase_pa + vec_size))
+			pr_err("Insufficient space for exception vectors\n");
+
+		memblock_reserve(ebase_pa, vec_size);
 	} else {
 		vec_size = max(vec_size, PAGE_SIZE);
 		ebase_pa = memblock_phys_alloc(vec_size, 1 << fls(vec_size));
-- 
2.34.1