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[PATCHv11,12/19] x86/mm: Make e820__end_ram_pfn() cover E820_TYPE_ACPI ranges

Message ID 20240528095522.509667-13-kirill.shutemov@linux.intel.com
State Superseded
Headers show
Series x86/tdx: Add kexec support | expand

Commit Message

Kirill A. Shutemov May 28, 2024, 9:55 a.m. UTC 
e820__end_of_ram_pfn() is used to calculate max_pfn which, among other
things, guides where direct mapping ends. Any memory above max_pfn is
not going to be present in the direct mapping.

e820__end_of_ram_pfn() finds the end of the RAM based on the highest
E820_TYPE_RAM range. But it doesn't includes E820_TYPE_ACPI ranges into
calculation.

Despite the name, E820_TYPE_ACPI covers not only ACPI data, but also EFI
tables and might be required by kernel to function properly.

Usually the problem is hidden because there is some E820_TYPE_RAM memory
above E820_TYPE_ACPI. But crashkernel only presents pre-allocated crash
memory as E820_TYPE_RAM on boot. If the preallocated range is small, it
can fit under the last E820_TYPE_ACPI range.

Modify e820__end_of_ram_pfn() and e820__end_of_low_ram_pfn() to cover
E820_TYPE_ACPI memory.

The problem was discovered during debugging kexec for TDX guest. TDX
guest uses E820_TYPE_ACPI to store the unaccepted memory bitmap and pass
it between the kernels on kexec.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Tested-by: Tao Liu <ltao@redhat.com>
---
 arch/x86/kernel/e820.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)
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Patch

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 68b09f718f10..4893d30ce438 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -828,7 +828,7 @@  u64 __init e820__memblock_alloc_reserved(u64 size, u64 align)
 /*
  * Find the highest page frame number we have available
  */
-static unsigned long __init e820_end_pfn(unsigned long limit_pfn, enum e820_type type)
+static unsigned long __init e820__end_ram_pfn(unsigned long limit_pfn)
 {
 	int i;
 	unsigned long last_pfn = 0;
@@ -839,7 +839,8 @@  static unsigned long __init e820_end_pfn(unsigned long limit_pfn, enum e820_type
 		unsigned long start_pfn;
 		unsigned long end_pfn;
 
-		if (entry->type != type)
+		if (entry->type != E820_TYPE_RAM &&
+		    entry->type != E820_TYPE_ACPI)
 			continue;
 
 		start_pfn = entry->addr >> PAGE_SHIFT;
@@ -865,12 +866,12 @@  static unsigned long __init e820_end_pfn(unsigned long limit_pfn, enum e820_type
 
 unsigned long __init e820__end_of_ram_pfn(void)
 {
-	return e820_end_pfn(MAX_ARCH_PFN, E820_TYPE_RAM);
+	return e820__end_ram_pfn(MAX_ARCH_PFN);
 }
 
 unsigned long __init e820__end_of_low_ram_pfn(void)
 {
-	return e820_end_pfn(1UL << (32 - PAGE_SHIFT), E820_TYPE_RAM);
+	return e820__end_ram_pfn(1UL << (32 - PAGE_SHIFT));
 }
 
 static void __init early_panic(char *msg)