E820 reserved ranges is useful in kdump kernel, it has been added in
kexec-tools code.
One reason is PCI mmconf (extended mode) requires reserved region otherwise
it falls back to legacy mode, and also outputs the following kernel log.
Example:
......
[ 19.798354] PCI: MMCONFIG for domain 0000 [bus 00-ff] at [mem 0x80000000-0x8fffffff] (base 0x80000000)
[ 19.800653] [Firmware Info]: PCI: MMCONFIG at [mem 0x80000000-0x8fffffff] not reserved in ACPI motherboard resources
[ 19.800995] PCI: not using MMCONFIG
......
The correct kernel log is like this:
......
[ 0.082649] PCI: MMCONFIG for domain 0000 [bus 00-ff] at [mem 0x80000000-0x8fffffff] (base 0x80000000)
[ 0.083610] PCI: MMCONFIG at [mem 0x80000000-0x8fffffff] reserved in E820
......
Furthermore, when AMD SME kdump support, it needs to map dmi table area
as decrypted. For normal boot, these ranges sit in e820 reserved ranges,
thus the early ioremap code naturally map them as decrypted. If it also
has same e820 reserve setup in kdump kernel then it will just work like
normal kernel.
Suggested-by: Dave Young <dyoung@xxxxxxxxxx>
Signed-off-by: Lianbo Jiang <lijiang@xxxxxxxxxx>
---
arch/x86/kernel/crash.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index ae724a6e0a5f..d3167125800e 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -384,6 +384,10 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
walk_iomem_res_desc(IORES_DESC_ACPI_NV_STORAGE, flags, 0, -1, &cmd,
memmap_entry_callback);
+ cmd.type = E820_TYPE_RESERVED;
+ walk_iomem_res_desc(IORES_DESC_NONE, 0, 0, -1, &cmd,
+ memmap_entry_callback);
+
/* Add crashk_low_res region */
if (crashk_low_res.end) {
ei.addr = crashk_low_res.start;
--
2.17.1
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