linux-kernel - [PATCH v2 2/3] arm64: kdump: do not map crashkernel region specifically

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Date:   Fri,  7 Apr 2023 09:15:06 +0800
From:   Baoquan He <bhe@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     catalin.marinas@....com, rppt@...nel.org,
        thunder.leizhen@...wei.com, will@...nel.org, ardb@...nel.org,
        horms@...nel.org, John.p.donnelly@...cle.com,
        kexec@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
        Baoquan He <bhe@...hat.com>
Subject: [PATCH v2 2/3] arm64: kdump: do not map crashkernel region specifically

After taking off the protection functions on crashkernel memory region,
there's no need to map crashkernel region with page granularity during
linear mapping.

With this change, the system can make use of block or section mapping
on linear region to largely improve perforcemence during system bootup
and running.

Signed-off-by: Baoquan He <bhe@...hat.com>
Acked-by: Catalin Marinas <catalin.marinas@....com>
Acked-by: Mike Rapoport (IBM) <rppt@...nel.org>
Reviewed-by: Zhen Lei <thunder.leizhen@...wei.com>
---
 arch/arm64/mm/mmu.c | 43 -------------------------------------------
 1 file changed, 43 deletions(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 6f9d8898a025..7556020a27b7 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -510,21 +510,6 @@ void __init mark_linear_text_alias_ro(void)
 			    PAGE_KERNEL_RO);
 }
 
-static bool crash_mem_map __initdata;
-
-static int __init enable_crash_mem_map(char *arg)
-{
-	/*
-	 * Proper parameter parsing is done by reserve_crashkernel(). We only
-	 * need to know if the linear map has to avoid block mappings so that
-	 * the crashkernel reservations can be unmapped later.
-	 */
-	crash_mem_map = true;
-
-	return 0;
-}
-early_param("crashkernel", enable_crash_mem_map);
-
 static void __init map_mem(pgd_t *pgdp)
 {
 	static const u64 direct_map_end = _PAGE_END(VA_BITS_MIN);
@@ -554,16 +539,6 @@ static void __init map_mem(pgd_t *pgdp)
 	 */
 	memblock_mark_nomap(kernel_start, kernel_end - kernel_start);
 
-#ifdef CONFIG_KEXEC_CORE
-	if (crash_mem_map) {
-		if (defer_reserve_crashkernel())
-			flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
-		else if (crashk_res.end)
-			memblock_mark_nomap(crashk_res.start,
-			    resource_size(&crashk_res));
-	}
-#endif
-
 	/* map all the memory banks */
 	for_each_mem_range(i, &start, &end) {
 		if (start >= end)
@@ -590,24 +565,6 @@ static void __init map_mem(pgd_t *pgdp)
 	__map_memblock(pgdp, kernel_start, kernel_end,
 		       PAGE_KERNEL, NO_CONT_MAPPINGS);
 	memblock_clear_nomap(kernel_start, kernel_end - kernel_start);
-
-	/*
-	 * Use page-level mappings here so that we can shrink the region
-	 * in page granularity and put back unused memory to buddy system
-	 * through /sys/kernel/kexec_crash_size interface.
-	 */
-#ifdef CONFIG_KEXEC_CORE
-	if (crash_mem_map && !defer_reserve_crashkernel()) {
-		if (crashk_res.end) {
-			__map_memblock(pgdp, crashk_res.start,
-				       crashk_res.end + 1,
-				       PAGE_KERNEL,
-				       NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS);
-			memblock_clear_nomap(crashk_res.start,
-					     resource_size(&crashk_res));
-		}
-	}
-#endif
 }
 
 void mark_rodata_ro(void)
-- 
2.34.1