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authorDavid Hildenbrand <david@redhat.com>2021-11-09 05:31:48 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2021-11-09 21:02:48 +0300
commitcc5f2704c93456e6f1c671c5cf7b582a55df5484 (patch)
treef407b00013ea6cf043f9c3bfea7b2e262bb5d833 /include/linux/crash_dump.h
parent2c9feeaedfe1f34c4e327cb6f9b8b90052edced1 (diff)
downloadlinux-cc5f2704c93456e6f1c671c5cf7b582a55df5484.tar.xz
proc/vmcore: convert oldmem_pfn_is_ram callback to more generic vmcore callbacks
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>
Diffstat (limited to 'include/linux/crash_dump.h')
-rw-r--r--include/linux/crash_dump.h26
1 files changed, 23 insertions, 3 deletions
diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h
index 2618577a4d6d..0c547d866f1e 100644
--- a/include/linux/crash_dump.h
+++ b/include/linux/crash_dump.h
@@ -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; }