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proc/vmcore: convert oldmem_pfn_is_ram callback to more generic vmcore callbacks

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Let's support multiple registered callbacks, making sure that
registering vmcore callbacks cannot fail.  Make the callback return a
bool instead of an int, handling how to deal with errors internally.
Drop unused HAVE_OLDMEM_PFN_IS_RAM.

We soon want to make use of this infrastructure from other drivers:
virtio-mem, registering one callback for each virtio-mem device, to
prevent reading unplugged virtio-mem memory.

Handle it via a generic vmcore_cb structure, prepared for future
extensions: for example, once we support virtio-mem on s390x where the
vmcore is completely constructed in the second kernel, we want to detect
and add plugged virtio-mem memory ranges to the vmcore in order for them
to get dumped properly.

Handle corner cases that are unexpected and shouldn't happen in sane
setups: registering a callback after the vmcore has already been opened
(warn only) and unregistering a callback after the vmcore has already been
opened (warn and essentially read only zeroes from that point on).

Link: https://lkml.kernel.org/r/20211005121430.30136-6-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Hildenbrand
2021-11-08 18:31:48 -08:00
committed by Linus Torvalds
parent 2c9feeaedf
commit cc5f2704c9
4 changed files with 110 additions and 37 deletions
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26
include/linux/crash_dump.h
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@@ -91,9 +91,29 @@ static inline void vmcore_unusable(void)
elfcorehdr_addr = ELFCORE_ADDR_ERR;
}
#define HAVE_OLDMEM_PFN_IS_RAM 1
extern int register_oldmem_pfn_is_ram(int (*fn)(unsigned long pfn));
extern void unregister_oldmem_pfn_is_ram(void);
/**
* struct vmcore_cb - driver callbacks for /proc/vmcore handling
* @pfn_is_ram: check whether a PFN really is RAM and should be accessed when
* reading the vmcore. Will return "true" if it is RAM or if the
* callback cannot tell. If any callback returns "false", it's not
* RAM and the page must not be accessed; zeroes should be
* indicated in the vmcore instead. For example, a ballooned page
* contains no data and reading from such a page will cause high
* load in the hypervisor.
* @next: List head to manage registered callbacks internally; initialized by
* register_vmcore_cb().
*
* vmcore callbacks allow drivers managing physical memory ranges to
* coordinate with vmcore handling code, for example, to prevent accessing
* physical memory ranges that should not be accessed when reading the vmcore,
* although included in the vmcore header as memory ranges to dump.
*/
struct vmcore_cb {
bool (*pfn_is_ram)(struct vmcore_cb *cb, unsigned long pfn);
struct list_head next;
};
extern void register_vmcore_cb(struct vmcore_cb *cb);
extern void unregister_vmcore_cb(struct vmcore_cb *cb);
#else /* !CONFIG_CRASH_DUMP */
static inline bool is_kdump_kernel(void) { return 0; }