From: Zhen Lei thunder.leizhen@huawei.com
[ Upstream commit 1cba6c4309f03de570202c46f03df3f73a0d4c82 ]
Patch series "kexec: enable kexec_crash_size to support two crash kernel regions".
When crashkernel=X fails to reserve region under 4G, it will fall back to reserve region above 4G and a region of the default size will also be reserved under 4G. Unfortunately, /sys/kernel/kexec_crash_size only supports one crash kernel region now, the user cannot sense the low memory reserved by reading /sys/kernel/kexec_crash_size. Also, low memory cannot be freed by writing this file.
For example: resource_size(crashk_res) = 512M resource_size(crashk_low_res) = 256M
The result of 'cat /sys/kernel/kexec_crash_size' is 512M, but it should be 768M. When we execute 'echo 0 > /sys/kernel/kexec_crash_size', the size of crashk_res becomes 0 and resource_size(crashk_low_res) is still 256 MB, which is incorrect.
Since crashk_res manages the memory with high address and crashk_low_res manages the memory with low address, crashk_low_res is shrunken only when all crashk_res is shrunken. And because when there is only one crash kernel region, crashk_res is always used. Therefore, if all crashk_res is shrunken and crashk_low_res still exists, swap them.
This patch (of 6):
If the value of parameter 'new_size' is in the semi-open and semi-closed interval (crashk_res.end - KEXEC_CRASH_MEM_ALIGN + 1, crashk_res.end], the calculation result of ram_res is:
ram_res->start = crashk_res.end + 1 ram_res->end = crashk_res.end
The operation of insert_resource() fails, and ram_res is not added to iomem_resource. As a result, the memory of the control block ram_res is leaked.
In fact, on all architectures, the start address and size of crashk_res are already aligned by KEXEC_CRASH_MEM_ALIGN. Therefore, we do not need to round up crashk_res.start again. Instead, we should round up 'new_size' in advance.
Link: https://lkml.kernel.org/r/20230527123439.772-1-thunder.leizhen@huawei.com Link: https://lkml.kernel.org/r/20230527123439.772-2-thunder.leizhen@huawei.com Fixes: 6480e5a09237 ("kdump: add missing RAM resource in crash_shrink_memory()") Fixes: 06a7f711246b ("kexec: premit reduction of the reserved memory size") Signed-off-by: Zhen Lei thunder.leizhen@huawei.com Acked-by: Baoquan He bhe@redhat.com Cc: Cong Wang amwang@redhat.com Cc: Eric W. Biederman ebiederm@xmission.com Cc: Michael Holzheu holzheu@linux.vnet.ibm.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/kexec_core.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c index 27cf24e285e0c..3d87dcbb9cbd6 100644 --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -1016,6 +1016,7 @@ int crash_shrink_memory(unsigned long new_size) start = crashk_res.start; end = crashk_res.end; old_size = (end == 0) ? 0 : end - start + 1; + new_size = roundup(new_size, KEXEC_CRASH_MEM_ALIGN); if (new_size >= old_size) { ret = (new_size == old_size) ? 0 : -EINVAL; goto unlock; @@ -1027,9 +1028,7 @@ int crash_shrink_memory(unsigned long new_size) goto unlock; }
- start = roundup(start, KEXEC_CRASH_MEM_ALIGN); - end = roundup(start + new_size, KEXEC_CRASH_MEM_ALIGN); - + end = start + new_size; crash_free_reserved_phys_range(end, crashk_res.end);
if ((start == end) && (crashk_res.parent != NULL))