On 01.05.20 18:57, James Morse wrote: > On x86, the kexec payload contains a copy of the current memory map. > If memory is added or removed, this copy of the memory map becomes > stale. Getting this wrong may prevent the next kernel from booting. > The first kernel may die if it tries to re-assemble the next kernel > in memory that has been removed. > > Discard the loaded kexec image when the memory map changes, user-space > should reload it. > > Kdump is unaffected, as it is placed within the crashkernel reserved > memory area and only uses this memory. The stale memory map may affect > generation of the vmcore, but the kdump kernel should be in a position > to validate it. > > Signed-off-by: James Morse <james.morse@xxxxxxx> > --- > This patch obsoletes: > * kexec/memory_hotplug: Prevent removal and accidental use > https://lore.kernel.org/linux-arm-kernel/20200326180730.4754-1-james.morse@xxxxxxx/ > > kernel/kexec_core.c | 40 ++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 40 insertions(+) > > diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c > index c19c0dad1ebe..e1901e5bd4b5 100644 > --- a/kernel/kexec_core.c > +++ b/kernel/kexec_core.c > @@ -12,6 +12,7 @@ > #include <linux/slab.h> > #include <linux/fs.h> > #include <linux/kexec.h> > +#include <linux/memory.h> > #include <linux/mutex.h> > #include <linux/list.h> > #include <linux/highmem.h> > @@ -22,10 +23,12 @@ > #include <linux/elf.h> > #include <linux/elfcore.h> > #include <linux/utsname.h> > +#include <linux/notifier.h> > #include <linux/numa.h> > #include <linux/suspend.h> > #include <linux/device.h> > #include <linux/freezer.h> > +#include <linux/pfn.h> > #include <linux/pm.h> > #include <linux/cpu.h> > #include <linux/uaccess.h> > @@ -1219,3 +1222,40 @@ void __weak arch_kexec_protect_crashkres(void) > > void __weak arch_kexec_unprotect_crashkres(void) > {} > + > +/* > + * If the memory layout changes, any loaded kexec image should be evicted > + * as it may contain a copy of the (now stale) memory map. This also means > + * we don't need to check the memory is still present when re-assembling the > + * new kernel at machine_kexec() time. > + */ Onlining/offlining is not a change of the memory map. -- Thanks, David / dhildenb
