Re: [PATCH v3 3/3] device-dax: Add memory via add_memory_driver_managed()
> Currently, when adding memory, we create entries in /sys/firmware/memmap/ > as "System RAM". This will lead to kexec-tools to add that memory to the > fixed-up initial memmap for a kexec kernel (loaded via kexec_load()). The > memory will be considered initial System RAM by the kexec'd kernel and > can no longer be reconfigured. This is not what happens during a real > reboot. > > Let's add our memory via add_memory_driver_managed() now, so we won't > create entries in /sys/firmware/memmap/ and indicate the memory as > "System RAM (kmem)" in /proc/iomem. This allows everybody (especially > kexec-tools) to identify that this memory is special and has to be treated > differently than ordinary (hotplugged) System RAM. > > Before configuring the namespace: > [root@localhost ~]# cat /proc/iomem > ... > 14000-33fff : Persistent Memory > 14000-33fff : namespace0.0 > 328000-32 : PCI Bus :00 > > After configuring the namespace: > [root@localhost ~]# cat /proc/iomem > ... > 14000-33fff : Persistent Memory > 14000-1481f : namespace0.0 > 14820-33fff : dax0.0 > 328000-32 : PCI Bus :00 > > After loading kmem before this change: > [root@localhost ~]# cat /proc/iomem > ... > 14000-33fff : Persistent Memory > 14000-1481f : namespace0.0 > 15000-33fff : dax0.0 > 15000-33fff : System RAM > 328000-32 : PCI Bus :00 > > After loading kmem after this change: > [root@localhost ~]# cat /proc/iomem > ... > 14000-33fff : Persistent Memory > 14000-1481f : namespace0.0 > 15000-33fff : dax0.0 > 15000-33fff : System RAM (kmem) > 328000-32 : PCI Bus :00 > > After a proper reboot: > [root@localhost ~]# cat /proc/iomem > ... > 14000-33fff : Persistent Memory > 14000-1481f : namespace0.0 > 14820-33fff : dax0.0 > 328000-32 : PCI Bus :00 > > Within the kexec kernel before this change: > [root@localhost ~]# cat /proc/iomem > ... > 14000-33fff : Persistent Memory > 14000-1481f : namespace0.0 > 15000-33fff : System RAM > 328000-32 : PCI Bus :00 > > Within the kexec kernel after this change: > [root@localhost ~]# cat /proc/iomem > ... > 14000-33fff : Persistent Memory > 14000-1481f : namespace0.0 > 14820-33fff : dax0.0 > 328000-32 : PCI Bus :00 > > /sys/firmware/memmap/ before this change: > -0009fc00 (System RAM) > 0009fc00-000a (Reserved) > 000f-0010 (Reserved) > 0010-bffdf000 (System RAM) > bffdf000-c000 (Reserved) > feffc000-ff00 (Reserved) > fffc-0001 (Reserved) > 0001-00014000 (System RAM) > 00015000-00034000 (System RAM) > > /sys/firmware/memmap/ after a proper reboot: > -0009fc00 (System RAM) > 0009fc00-000a (Reserved) > 000f-0010 (Reserved) > 0010-bffdf000 (System RAM) > bffdf000-c000 (Reserved) > feffc000-ff00 (Reserved) > fffc-0001 (Reserved) > 0001-00014000 (System RAM) > > /sys/firmware/memmap/ after this change: > -0009fc00 (System RAM) > 0009fc00-000a (Reserved) > 000f-0010 (Reserved) > 0010-bffdf000 (System RAM) > bffdf000-c000 (Reserved) > feffc000-ff00 (Reserved) > fffc-0001 (Reserved) > 0001-00014000 (System RAM) > > kexec-tools already seem to basically ignore any System RAM that's not > on top level when searching for areas to place kexec images - but also > for determining crash areas to dump via kdump. Changing the resource name > won't have an impact. > > Cc: Andrew Morton > Cc: Michal Hocko > Cc: Pankaj Gupta > Cc: Wei Yang > Cc: Baoquan He > Cc: Dave Hansen > Cc: Eric Biederman > Cc: Pavel Tatashin > Cc: Dan Williams > Signed-off-by: David Hildenbrand > --- > drivers/dax/kmem.c | 8 +++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c > index 3d0a7e702c94..5a645a24e359 100644
[PATCH v3 3/3] device-dax: Add memory via add_memory_driver_managed()
Currently, when adding memory, we create entries in /sys/firmware/memmap/ as "System RAM". This will lead to kexec-tools to add that memory to the fixed-up initial memmap for a kexec kernel (loaded via kexec_load()). The memory will be considered initial System RAM by the kexec'd kernel and can no longer be reconfigured. This is not what happens during a real reboot. Let's add our memory via add_memory_driver_managed() now, so we won't create entries in /sys/firmware/memmap/ and indicate the memory as "System RAM (kmem)" in /proc/iomem. This allows everybody (especially kexec-tools) to identify that this memory is special and has to be treated differently than ordinary (hotplugged) System RAM. Before configuring the namespace: [root@localhost ~]# cat /proc/iomem ... 14000-33fff : Persistent Memory 14000-33fff : namespace0.0 328000-32 : PCI Bus :00 After configuring the namespace: [root@localhost ~]# cat /proc/iomem ... 14000-33fff : Persistent Memory 14000-1481f : namespace0.0 14820-33fff : dax0.0 328000-32 : PCI Bus :00 After loading kmem before this change: [root@localhost ~]# cat /proc/iomem ... 14000-33fff : Persistent Memory 14000-1481f : namespace0.0 15000-33fff : dax0.0 15000-33fff : System RAM 328000-32 : PCI Bus :00 After loading kmem after this change: [root@localhost ~]# cat /proc/iomem ... 14000-33fff : Persistent Memory 14000-1481f : namespace0.0 15000-33fff : dax0.0 15000-33fff : System RAM (kmem) 328000-32 : PCI Bus :00 After a proper reboot: [root@localhost ~]# cat /proc/iomem ... 14000-33fff : Persistent Memory 14000-1481f : namespace0.0 14820-33fff : dax0.0 328000-32 : PCI Bus :00 Within the kexec kernel before this change: [root@localhost ~]# cat /proc/iomem ... 14000-33fff : Persistent Memory 14000-1481f : namespace0.0 15000-33fff : System RAM 328000-32 : PCI Bus :00 Within the kexec kernel after this change: [root@localhost ~]# cat /proc/iomem ... 14000-33fff : Persistent Memory 14000-1481f : namespace0.0 14820-33fff : dax0.0 328000-32 : PCI Bus :00 /sys/firmware/memmap/ before this change: -0009fc00 (System RAM) 0009fc00-000a (Reserved) 000f-0010 (Reserved) 0010-bffdf000 (System RAM) bffdf000-c000 (Reserved) feffc000-ff00 (Reserved) fffc-0001 (Reserved) 0001-00014000 (System RAM) 00015000-00034000 (System RAM) /sys/firmware/memmap/ after a proper reboot: -0009fc00 (System RAM) 0009fc00-000a (Reserved) 000f-0010 (Reserved) 0010-bffdf000 (System RAM) bffdf000-c000 (Reserved) feffc000-ff00 (Reserved) fffc-0001 (Reserved) 0001-00014000 (System RAM) /sys/firmware/memmap/ after this change: -0009fc00 (System RAM) 0009fc00-000a (Reserved) 000f-0010 (Reserved) 0010-bffdf000 (System RAM) bffdf000-c000 (Reserved) feffc000-ff00 (Reserved) fffc-0001 (Reserved) 0001-00014000 (System RAM) kexec-tools already seem to basically ignore any System RAM that's not on top level when searching for areas to place kexec images - but also for determining crash areas to dump via kdump. Changing the resource name won't have an impact. Cc: Andrew Morton Cc: Michal Hocko Cc: Pankaj Gupta Cc: Wei Yang Cc: Baoquan He Cc: Dave Hansen Cc: Eric Biederman Cc: Pavel Tatashin Cc: Dan Williams Signed-off-by: David Hildenbrand --- drivers/dax/kmem.c | 8 +++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c index 3d0a7e702c94..5a645a24e359 100644 --- a/drivers/dax/kmem.c +++ b/drivers/dax/kmem.c @@ -65,7 +65,13 @@ int dev_dax_kmem_probe(struct device *dev) new_res->flags = IORESOURCE_SYSTEM_RAM; new_res->name = dev_name(dev); - rc =
