47a91b7232
There is a panic in armv8a server(QDF2400) under memory pressure tests (start 20 guests and run memhog in the host). ---------------------------------begin-------------------------------- [35380.800950] BUG: Bad page state in process qemu-kvm pfn:dd0b6 [35380.805825] page:ffff7fe003742d80 count:-4871 mapcount:-2126053375 mapping: (null) index:0x0 [35380.815024] flags: 0x1fffc00000000000() [35380.818845] raw: 1fffc00000000000 0000000000000000 0000000000000000 ffffecf981470000 [35380.826569] raw: dead000000000100 dead000000000200 ffff8017c001c000 0000000000000000 [35380.805825] page:ffff7fe003742d80 count:-4871 mapcount:-2126053375 mapping: (null) index:0x0 [35380.815024] flags: 0x1fffc00000000000() [35380.818845] raw: 1fffc00000000000 0000000000000000 0000000000000000 ffffecf981470000 [35380.826569] raw: dead000000000100 dead000000000200 ffff8017c001c000 0000000000000000 [35380.834294] page dumped because: nonzero _refcount [...] --------------------------------end-------------------------------------- The root cause might be what was fixed at [1]. But from the KVM points of view, it would be better if the issue was caught earlier. If the size is not PAGE_SIZE aligned, unmap_stage2_range might unmap the wrong(more or less) page range. Hence it caused the "BUG: Bad page state" Let's WARN in that case, so that the issue is obvious. [1] https://lkml.org/lkml/2018/5/3/1042 Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com> Signed-off-by: jia.he@hxt-semitech.com [maz: tidied up commit message] Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.