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From:   Lianbo Jiang <lijiang@redhat.com>
To:     linux-kernel@vger.kernel.org
Cc:     linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org,
        x86@kernel.org, ardb@kernel.org, tglx@linutronix.de,
        mingo@redhat.com, bp@alien8.de, dvhart@infradead.org,
        andy@infradead.org, hpa@zytor.com, kexec@lists.infradead.org,
        bhe@redhat.com, dyoung@redhat.com
Subject: [PATCH] x86/efi: Do not release sub-1MB memory regions when the crashkernel option is specified
Date:   Wed,  7 Apr 2021 22:03:16 +0800
Message-Id: <20210407140316.30210-1-lijiang@redhat.com>
Precedence: bulk

Some sub-1MB memory regions may be reserved by EFI boot services, and the
memory regions will be released later in the efi_free_boot_services().

Currently, always reserve all sub-1MB memory regions when the crashkernel
option is specified, but unfortunately EFI boot services may have already
reserved some sub-1MB memory regions before the crash_reserve_low_1M() is
called, which makes that the crash_reserve_low_1M() only own the
remaining sub-1MB memory regions, not all sub-1MB memory regions, because,
subsequently EFI boot services will free its own sub-1MB memory regions.
Eventually, DMA will be able to allocate memory from the sub-1MB area and
cause the following error:

crash> kmem -s |grep invalid
kmem: dma-kmalloc-512: slab: ffffd52c40001900 invalid freepointer: ffff9403c0067300
kmem: dma-kmalloc-512: slab: ffffd52c40001900 invalid freepointer: ffff9403c0067300
crash> vtop ffff9403c0067300
VIRTUAL           PHYSICAL
ffff9403c0067300  67300   --->The physical address falls into this range [0x0000000000063000-0x000000000008efff]

kernel debugging log:
...
[    0.008927] memblock_reserve: [0x0000000000010000-0x0000000000013fff] efi_reserve_boot_services+0x85/0xd0
[    0.008930] memblock_reserve: [0x0000000000063000-0x000000000008efff] efi_reserve_boot_services+0x85/0xd0
...
[    0.009425] memblock_reserve: [0x0000000000000000-0x00000000000fffff] crash_reserve_low_1M+0x2c/0x49
...
[    0.010586] Zone ranges:
[    0.010587]   DMA      [mem 0x0000000000001000-0x0000000000ffffff]
[    0.010589]   DMA32    [mem 0x0000000001000000-0x00000000ffffffff]
[    0.010591]   Normal   [mem 0x0000000100000000-0x0000000c7fffffff]
[    0.010593]   Device   empty
...
[    8.814894] __memblock_free_late: [0x0000000000063000-0x000000000008efff] efi_free_boot_services+0x14b/0x23b
[    8.815793] __memblock_free_late: [0x0000000000010000-0x0000000000013fff] efi_free_boot_services+0x14b/0x23b

Do not release sub-1MB memory regions even though they are reserved by
EFI boot services, so that always reserve all sub-1MB memory regions when
the crashkernel option is specified.

Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
---
 arch/x86/platform/efi/quirks.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
index 67d93a243c35..637f932c4fd4 100644
--- a/arch/x86/platform/efi/quirks.c
+++ b/arch/x86/platform/efi/quirks.c
@@ -18,6 +18,7 @@
 #include <asm/cpu_device_id.h>
 #include <asm/realmode.h>
 #include <asm/reboot.h>
+#include <asm/cmdline.h>
 
 #define EFI_MIN_RESERVE 5120
 
@@ -303,6 +304,19 @@ void __init efi_arch_mem_reserve(phys_addr_t addr, u64 size)
  */
 static __init bool can_free_region(u64 start, u64 size)
 {
+	/*
+	 * Some sub-1MB memory regions may be reserved by EFI boot
+	 * services, and these memory regions will be released later
+	 * in the efi_free_boot_services().
+	 *
+	 * Do not release sub-1MB memory regions even though they are
+	 * reserved by EFI boot services, because, always reserve all
+	 * sub-1MB memory when the crashkernel option is specified.
+	 */
+	if (cmdline_find_option(boot_command_line, "crashkernel", NULL, 0) > 0
+		&& (start + size < (1<<20)))
+		return false;
+
 	if (start + size > __pa_symbol(_text) && start <= __pa_symbol(_end))
 		return false;
 
-- 
2.17.1