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Date: Thu, 14 Nov 2019 11:10:19 -0500
From: Masayoshi Mizuma <msys.mizuma@...il.com>
To: Ard Biesheuvel <ard.biesheuvel@...aro.org>,
linux-arm-kernel@...ts.infradead.org, linux-efi@...r.kernel.org
Cc: Masayoshi Mizuma <msys.mizuma@...il.com>,
Masayoshi Mizuma <m.mizuma@...fujitsu.com>,
linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
d.hatayama@...itsu.com
Subject: [RFC PATCH v2] efi: arm64: Introduce /sys/firmware/efi/memreserve to tell the persistent pages
From: Masayoshi Mizuma <m.mizuma@...fujitsu.com>
kexec reboot stops in early boot sequence because efi_config_parse_tables()
refers garbage data. We can see the log with memblock=debug kernel option:
efi: ACPI 2.0=0x9821790014 PROP=0x8757f5c0 SMBIOS 3.0=0x9820740000 MEMRESERVE=0x9820bfdc58
memblock_reserve: [0x0000009820bfdc58-0x0000009820bfdc67] efi_config_parse_tables+0x228/0x278
memblock_reserve: [0x0000000082760000-0x00000000324d07ff] efi_config_parse_tables+0x228/0x278
memblock_reserve: [0xcc4f84ecc0511670-0x5f6e5214a7fd91f9] efi_config_parse_tables+0x244/0x278
memblock_reserve: [0xd2fd4144b9af693d-0xad0c1db1086f40a2] efi_config_parse_tables+0x244/0x278
memblock_reserve: [0x0c719bb159b1fadc-0x5aa6e62a1417ce12] efi_config_parse_tables+0x244/0x278
...
That happens because 0x82760000, struct linux_efi_memreserve, is destroyed.
0x82760000 is pointed from efi.mem_reseve, and efi.mem_reserve points the
head page of LPI pending table and LPI property table which are allocated by
gic_reserve_range().
The destroyer is kexec. kexec locates the initrd to the area:
]# kexec -d -l /boot/vmlinuz-5.4.0-rc7 /boot/initramfs-5.4.0-rc7.img --reuse-cmdline
...
initrd: base 82290000, size 388dd8ah (59301258)
...
>From dynamic debug log. initrd is located in segment[1]:
machine_kexec_prepare:70:
kexec kimage info:
type: 0
start: 85b30680
head: 0
nr_segments: 4
segment[0]: 0000000080480000 - 0000000082290000, 0x1e10000 bytes, 481 pages
segment[1]: 0000000082290000 - 0000000085b20000, 0x3890000 bytes, 905 pages
segment[2]: 0000000085b20000 - 0000000085b30000, 0x10000 bytes, 1 pages
segment[3]: 0000000085b30000 - 0000000085b40000, 0x10000 bytes, 1 pages
kexec searches the memory region to locate initrd through
"System RAM" in /proc/iomem. The pending tables are included in
"System RAM" because they are allocated by alloc_pages(), so kexec
destroys the LPI pending tables.
Introduce /sys/firmware/efi/memreserve to tell the pages pointed by
efi.mem_reserve so that kexec can avoid the area to locate initrd.
Signed-off-by: Masayoshi Mizuma <m.mizuma@...fujitsu.com>
---
drivers/firmware/efi/efi.c | 41 +++++++++++++++++++++++++++++++++++++-
1 file changed, 40 insertions(+), 1 deletion(-)
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 0b6b0c19a..07812d697 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -149,6 +149,45 @@ static ssize_t systab_show(struct kobject *kobj,
static struct kobj_attribute efi_attr_systab = __ATTR_RO_MODE(systab, 0400);
+static struct linux_efi_memreserve *efi_memreserve_root __ro_after_init;
+static ssize_t memreserve_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ struct linux_efi_memreserve *rsv;
+ phys_addr_t start, end;
+ unsigned long prsv;
+ char *str = buf;
+ int count, i;
+
+ if (!kobj || !buf)
+ return -EINVAL;
+
+ if ((efi_memreserve_root == (void *)ULONG_MAX) ||
+ (!efi_memreserve_root))
+ return -ENODEV;
+
+ for (prsv = efi_memreserve_root->next; prsv; prsv = rsv->next) {
+ rsv = memremap(prsv, sizeof(*rsv), MEMREMAP_WB);
+ if (!rsv) {
+ pr_err("Could not map efi_memreserve\n");
+ return -ENOMEM;
+ }
+ count = atomic_read(&rsv->count);
+ for (i = 0; i < count; i++) {
+ start = rsv->entry[i].base;
+ end = start + rsv->entry[i].size - 1;
+
+ str += sprintf(str, "%pa-%pa\n", &start, &end);
+ }
+ memunmap(rsv);
+ }
+
+ return str - buf;
+}
+
+static struct kobj_attribute efi_attr_memreserve =
+ __ATTR_RO_MODE(memreserve, 0444);
+
#define EFI_FIELD(var) efi.var
#define EFI_ATTR_SHOW(name) \
@@ -180,6 +219,7 @@ static struct attribute *efi_subsys_attrs[] = {
&efi_attr_runtime.attr,
&efi_attr_config_table.attr,
&efi_attr_fw_platform_size.attr,
+ &efi_attr_memreserve.attr,
NULL,
};
@@ -964,7 +1004,6 @@ int efi_status_to_err(efi_status_t status)
}
static DEFINE_SPINLOCK(efi_mem_reserve_persistent_lock);
-static struct linux_efi_memreserve *efi_memreserve_root __ro_after_init;
static int __init efi_memreserve_map_root(void)
{
--
2.21.0
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