[PATCH 2/2] x86/setup: merge several reservations of start of the memory

Mike Rapoport
2021-01-15T08:33:33Z

From: Mike Rapoport <rppt@linux.ibm.com>

Currently the first several pages are reserved both to avoid leaking their
contents on systems with L1TF and to avoid corrupting BIOS memory.

Merge the two memory reservations.

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
---
arch/x86/kernel/setup.c | 29 +++++++++++------------------
1 file changed, 11 insertions(+), 18 deletions(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 32cd2e790a0a..3f2fd67240f8 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -715,20 +715,6 @@ static int __init parse_reservelow(char *p)

early_param("reservelow", parse_reservelow);

-static void __init trim_low_memory_range(void)
-{
- /*
- * A special case is the first 4Kb of memory;
- * This is a BIOS owned area, not kernel ram, but generally
- * not listed as such in the E820 table.
- *
- * This typically reserves additional memory (64KiB by default)
- * since some BIOSes are known to corrupt low memory. See the
- * Kconfig help text for X86_RESERVE_LOW.
- */
- memblock_reserve(0, ALIGN(reserve_low, PAGE_SIZE));
-}
-
static void __init early_reserve_memory(void)
{
/*
@@ -741,10 +727,18 @@ static void __init early_reserve_memory(void)
(unsigned long)__end_of_kernel_reserve - (unsigned long)_text);

/*
- * Make sure page 0 is always reserved because on systems with
- * L1TF its contents can be leaked to user processes.
+ * The first 4Kb of memory is a BIOS owned area, but generally it is
+ * not listed as such in the E820 table.
+ *
+ * Reserve the first memory page and typically some additional
+ * memory (64KiB by default) since some BIOSes are known to corrupt
+ * low memory. See the Kconfig help text for X86_RESERVE_LOW.
+ *
+ * In addition, we must make sure page 0 is always reserved because
+ * on systems with L1TF its contents can be leaked to user
+ * processes.
*/
- memblock_reserve(0, PAGE_SIZE);
+ memblock_reserve(0, ALIGN(reserve_low, PAGE_SIZE));

early_reserve_initrd();

@@ -757,7 +751,6 @@ static void __init early_reserve_memory(void)
reserve_bios_regions();

trim_platform_memory_ranges();
- trim_low_memory_range();
}

/*
--
2.28.0