On 8/10/21 11:55 AM, Mike Rapoport wrote:
On Mon, Aug 09, 2021 at 12:06:41PM -0700, Guenter Roeck wrote:
On Tue, Aug 03, 2021 at 09:42:18AM +0300, Mike Rapoport wrote:
From: Mike Rapoport <rppt@xxxxxxxxxxxxx>
There are a lot of uses of memblock_find_in_range() along with
memblock_reserve() from the times memblock allocation APIs did not exist.
memblock_find_in_range() is the very core of memblock allocations, so any
future changes to its internal behaviour would mandate updates of all the
users outside memblock.
Replace the calls to memblock_find_in_range() with an equivalent calls to
memblock_phys_alloc() and memblock_phys_alloc_range() and make
memblock_find_in_range() private method of memblock.
This simplifies the callers, ensures that (unlikely) errors in
memblock_reserve() are handled and improves maintainability of
memblock_find_in_range().
Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
I see a number of crashes in next-20210806 when booting x86 images from efi.
[ 0.000000] efi: EFI v2.70 by EDK II
[ 0.000000] efi: SMBIOS=0x1fbcc000 ACPI=0x1fbfa000 ACPI 2.0=0x1fbfa014 MEMATTR=0x1f25f018
[ 0.000000] SMBIOS 2.8 present.
[ 0.000000] DMI: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
[ 0.000000] last_pfn = 0x1ff50 max_arch_pfn = 0x400000000
[ 0.000000] x86/PAT: Configuration [0-7]: WB WC UC- UC WB WP UC- WT
[ 0.000000] Kernel panic - not syncing: alloc_low_pages: can not alloc memory
[ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.14.0-rc4-next-20210806 #1
[ 0.000000] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
[ 0.000000] Call Trace:
[ 0.000000] ? dump_stack_lvl+0x57/0x7d
[ 0.000000] ? panic+0xfc/0x2c6
[ 0.000000] ? alloc_low_pages+0x117/0x156
[ 0.000000] ? phys_pmd_init+0x234/0x342
[ 0.000000] ? phys_pud_init+0x171/0x337
[ 0.000000] ? __kernel_physical_mapping_init+0xec/0x276
[ 0.000000] ? init_memory_mapping+0x1ea/0x2aa
[ 0.000000] ? init_range_memory_mapping+0xdf/0x12e
[ 0.000000] ? init_mem_mapping+0x1e9/0x26f
[ 0.000000] ? setup_arch+0x5ff/0xb6d
[ 0.000000] ? start_kernel+0x71/0x6b4
[ 0.000000] ? secondary_startup_64_no_verify+0xc2/0xcb
Bisect points to this patch. Reverting it fixes the problem. Key seems to
be the amount of memory configured in qemu; the problem is not seen if
there is 1G or more of memory, but it is seen with all test boots with
512M or 256M of memory. It is also seen with almost all 32-bit efi boots.
The problem is not seen when booting without efi.
It looks like this change uncovered a problem in
x86::memory_map_top_down().
The allocation in alloc_low_pages() is limited by min_pfn_mapped and
max_pfn_mapped. The min_pfn_mapped is updated at every iteration of the
loop in memory_map_top_down, but there is another loop in
init_range_memory_mapping() that maps several regions below the current
min_pfn_mapped without updating this variable.
The memory layout in qemu with 256M of RAM and EFI enabled, causes
exhaustion of the memory limited by min_pfn_mapped and max_pfn_mapped
before min_pfn_mapped is updated.
Before this commit there was unconditional "reservation" of 2M in the end
of the memory that moved the initial min_pfn_mapped below the memory
reserved by EFI. The addition of check for xen_domain() removed this
reservation for !XEN and made alloc_low_pages() use the range already busy
with EFI data.
The patch below moves the update of min_pfn_mapped near the update of
max_pfn_mapped so that every time a new range is mapped both limits will be
updated accordingly.
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 1152a29ce109..be279f6e5a0a 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -1,3 +1,4 @@
+#define DEBUG
#include <linux/gfp.h>
#include <linux/initrd.h>
#include <linux/ioport.h>
@@ -485,6 +486,7 @@ static void add_pfn_range_mapped(unsigned long start_pfn, unsigned long end_pfn)
nr_pfn_mapped = clean_sort_range(pfn_mapped, E820_MAX_ENTRIES);
max_pfn_mapped = max(max_pfn_mapped, end_pfn);
+ min_pfn_mapped = min(min_pfn_mapped, start_pfn);
if (start_pfn < (1UL<<(32-PAGE_SHIFT)))
max_low_pfn_mapped = max(max_low_pfn_mapped,
@@ -643,7 +645,6 @@ static void __init memory_map_top_down(unsigned long map_start,
mapped_ram_size += init_range_memory_mapping(start,
last_start);
last_start = start;
- min_pfn_mapped = last_start >> PAGE_SHIFT;
if (mapped_ram_size >= step_size)
step_size = get_new_step_size(step_size);
}
The offending patch was removed from next-20210810, but I applied the above change
to next-20210809 and it does indeed fix the problem. If it is added as separate patch,
please feel free to add
Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Thanks,
Guenter
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