On 01/02/23 07:25, Michael Ellerman wrote:
Sourabh Jain <sourabhj...@linux.ibm.com> writes:
On 30/01/23 07:17, Michael Ellerman wrote:
In kexec_extra_fdt_size_ppc64() there's logic to estimate how much
extra space will be needed in the device tree for some memory related
properties.
That logic uses the size of RAM divided by drmem_lmb_size() to do the
estimation. However drmem_lmb_size() can be zero if the machine has no
hotpluggable memory configured, which is the case when booting with qemu
and no maxmem=x parameter is passed (the default).
The division by zero is reported by UBSAN, and can also lead to an
overflow and a warning from kvmalloc, and kdump kernel loading fails:
WARNING: CPU: 0 PID: 133 at mm/util.c:596 kvmalloc_node+0x15c/0x160
Modules linked in:
CPU: 0 PID: 133 Comm: kexec Not tainted 6.2.0-rc5-03455-g07358bd97810 #223
Hardware name: IBM pSeries (emulated by qemu) POWER9 (raw) 0x4e1200
0xf000005 of:SLOF,git-dd0dca pSeries
NIP: c00000000041ff4c LR: c00000000041fe58 CTR: 0000000000000000
REGS: c0000000096ef750 TRAP: 0700 Not tainted
(6.2.0-rc5-03455-g07358bd97810)
MSR: 800000000282b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 24248242
XER: 2004011e
CFAR: c00000000041fed0 IRQMASK: 0
...
NIP kvmalloc_node+0x15c/0x160
LR kvmalloc_node+0x68/0x160
Call Trace:
kvmalloc_node+0x68/0x160 (unreliable)
of_kexec_alloc_and_setup_fdt+0xb8/0x7d0
elf64_load+0x25c/0x4a0
kexec_image_load_default+0x58/0x80
sys_kexec_file_load+0x5c0/0x920
system_call_exception+0x128/0x330
system_call_vectored_common+0x15c/0x2ec
To fix it, skip the calculation if drmem_lmb_size() is zero.
Fixes: 2377c92e37fe ("powerpc/kexec_file: fix FDT size estimation for kdump
kernel")
Cc: sta...@vger.kernel.org # v5.12+
Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
---
arch/powerpc/kexec/file_load_64.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/kexec/file_load_64.c
b/arch/powerpc/kexec/file_load_64.c
index af8854f9eae3..3caee570e79b 100644
--- a/arch/powerpc/kexec/file_load_64.c
+++ b/arch/powerpc/kexec/file_load_64.c
@@ -989,10 +989,12 @@ unsigned int kexec_extra_fdt_size_ppc64(struct kimage
*image)
* linux,drconf-usable-memory properties. Get an approximate on the
* number of usable memory entries and use for FDT size estimation.
*/
- usm_entries = ((memblock_end_of_DRAM() / drmem_lmb_size()) +
- (2 * (resource_size(&crashk_res) / drmem_lmb_size())));
-
- extra_size = (unsigned int)(usm_entries * sizeof(u64));
+ if (drmem_lmb_size()) {
+ usm_entries = ((memblock_end_of_DRAM() / drmem_lmb_size()) +
+ (2 * (resource_size(&crashk_res) /
drmem_lmb_size())));
+ extra_size = (unsigned int)(usm_entries * sizeof(u64));
+ } else
+ extra_size = 0;
/*
* Get the number of CPU nodes in the current DT. This allows to
I failed to replicate this issue.
Qemu command used:
$ qemu-system-ppc64 -enable-kvm -smp 4,cores=2 -drive
file=my-image.qcow2 -nographic -m 2G
lsmem (inside guest):
RANGE SIZE STATE REMOVABLE BLOCK
0x0000000000000000-0x000000007fffffff 2G online yes 0-127
Memory block size: 16M
Total online memory: 2G
Total offline memory: 0B
Not sure what I am missing, but changes looks good to me.
Hmm, interesting.
Do you have /proc/device-tree/ibm,dynamic-reconfiguration-memory in the VM?
No I don't.
But if I add maxmem=x to qemu command line then ibm,dynamic-reconfiguration
DT node comes up.
What version of qemu are you using? I think I tested with 6.2 and 7.1.
QEMU emulator version 7.2.50 (v7.2.0-904-g13356edb87)
I tried with QEMU emulator version 7.1.0 (v7.1.0), but not able to
replicate it.
- Sourabh
