| Message ID | 20200504190227.18269-4-david@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm/memory_hotplug: Interface to add driver-managed system ram | expand |
> 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 > ... > 140000000-33fffffff : Persistent Memory > 140000000-33fffffff : namespace0.0 > 3280000000-32ffffffff : PCI Bus 0000:00 > > After configuring the namespace: > [root@localhost ~]# cat /proc/iomem > ... > 140000000-33fffffff : Persistent Memory > 140000000-1481fffff : namespace0.0 > 148200000-33fffffff : dax0.0 > 3280000000-32ffffffff : PCI Bus 0000:00 > > After loading kmem before this change: > [root@localhost ~]# cat /proc/iomem > ... > 140000000-33fffffff : Persistent Memory > 140000000-1481fffff : namespace0.0 > 150000000-33fffffff : dax0.0 > 150000000-33fffffff : System RAM > 3280000000-32ffffffff : PCI Bus 0000:00 > > After loading kmem after this change: > [root@localhost ~]# cat /proc/iomem > ... > 140000000-33fffffff : Persistent Memory > 140000000-1481fffff : namespace0.0 > 150000000-33fffffff : dax0.0 > 150000000-33fffffff : System RAM (kmem) > 3280000000-32ffffffff : PCI Bus 0000:00 > > After a proper reboot: > [root@localhost ~]# cat /proc/iomem > ... > 140000000-33fffffff : Persistent Memory > 140000000-1481fffff : namespace0.0 > 148200000-33fffffff : dax0.0 > 3280000000-32ffffffff : PCI Bus 0000:00 > > Within the kexec kernel before this change: > [root@localhost ~]# cat /proc/iomem > ... > 140000000-33fffffff : Persistent Memory > 140000000-1481fffff : namespace0.0 > 150000000-33fffffff : System RAM > 3280000000-32ffffffff : PCI Bus 0000:00 > > Within the kexec kernel after this change: > [root@localhost ~]# cat /proc/iomem > ... > 140000000-33fffffff : Persistent Memory > 140000000-1481fffff : namespace0.0 > 148200000-33fffffff : dax0.0 > 3280000000-32ffffffff : PCI Bus 0000:00 > > /sys/firmware/memmap/ before this change: > 0000000000000000-000000000009fc00 (System RAM) > 000000000009fc00-00000000000a0000 (Reserved) > 00000000000f0000-0000000000100000 (Reserved) > 0000000000100000-00000000bffdf000 (System RAM) > 00000000bffdf000-00000000c0000000 (Reserved) > 00000000feffc000-00000000ff000000 (Reserved) > 00000000fffc0000-0000000100000000 (Reserved) > 0000000100000000-0000000140000000 (System RAM) > 0000000150000000-0000000340000000 (System RAM) > > /sys/firmware/memmap/ after a proper reboot: > 0000000000000000-000000000009fc00 (System RAM) > 000000000009fc00-00000000000a0000 (Reserved) > 00000000000f0000-0000000000100000 (Reserved) > 0000000000100000-00000000bffdf000 (System RAM) > 00000000bffdf000-00000000c0000000 (Reserved) > 00000000feffc000-00000000ff000000 (Reserved) > 00000000fffc0000-0000000100000000 (Reserved) > 0000000100000000-0000000140000000 (System RAM) > > /sys/firmware/memmap/ after this change: > 0000000000000000-000000000009fc00 (System RAM) > 000000000009fc00-00000000000a0000 (Reserved) > 00000000000f0000-0000000000100000 (Reserved) > 0000000000100000-00000000bffdf000 (System RAM) > 00000000bffdf000-00000000c0000000 (Reserved) > 00000000feffc000-00000000ff000000 (Reserved) > 00000000fffc0000-0000000100000000 (Reserved) > 0000000100000000-0000000140000000 (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 <akpm@linux-foundation.org> > Cc: Michal Hocko <mhocko@suse.com> > Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com> > Cc: Wei Yang <richard.weiyang@gmail.com> > Cc: Baoquan He <bhe@redhat.com> > Cc: Dave Hansen <dave.hansen@linux.intel.com> > Cc: Eric Biederman <ebiederm@xmission.com> > Cc: Pavel Tatashin <pasha.tatashin@soleen.com> > Cc: Dan Williams <dan.j.williams@intel.com> > Signed-off-by: David Hildenbrand <david@redhat.com> > --- > 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 = add_memory(numa_node, new_res->start, resource_size(new_res)); > + /* > + * Ensure that future kexec'd kernels will not treat this as RAM > + * automatically. > + */ > + rc = add_memory_driver_managed(numa_node, new_res->start, > + resource_size(new_res), > + "System RAM (kmem)"); > if (rc) { > release_resource(new_res); > kfree(new_res); > -- Acked-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com> > 2.25.3 >
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 = add_memory(numa_node, new_res->start, resource_size(new_res)); + /* + * Ensure that future kexec'd kernels will not treat this as RAM + * automatically. + */ + rc = add_memory_driver_managed(numa_node, new_res->start, + resource_size(new_res), + "System RAM (kmem)"); if (rc) { release_resource(new_res); kfree(new_res);
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 ... 140000000-33fffffff : Persistent Memory 140000000-33fffffff : namespace0.0 3280000000-32ffffffff : PCI Bus 0000:00 After configuring the namespace: [root@localhost ~]# cat /proc/iomem ... 140000000-33fffffff : Persistent Memory 140000000-1481fffff : namespace0.0 148200000-33fffffff : dax0.0 3280000000-32ffffffff : PCI Bus 0000:00 After loading kmem before this change: [root@localhost ~]# cat /proc/iomem ... 140000000-33fffffff : Persistent Memory 140000000-1481fffff : namespace0.0 150000000-33fffffff : dax0.0 150000000-33fffffff : System RAM 3280000000-32ffffffff : PCI Bus 0000:00 After loading kmem after this change: [root@localhost ~]# cat /proc/iomem ... 140000000-33fffffff : Persistent Memory 140000000-1481fffff : namespace0.0 150000000-33fffffff : dax0.0 150000000-33fffffff : System RAM (kmem) 3280000000-32ffffffff : PCI Bus 0000:00 After a proper reboot: [root@localhost ~]# cat /proc/iomem ... 140000000-33fffffff : Persistent Memory 140000000-1481fffff : namespace0.0 148200000-33fffffff : dax0.0 3280000000-32ffffffff : PCI Bus 0000:00 Within the kexec kernel before this change: [root@localhost ~]# cat /proc/iomem ... 140000000-33fffffff : Persistent Memory 140000000-1481fffff : namespace0.0 150000000-33fffffff : System RAM 3280000000-32ffffffff : PCI Bus 0000:00 Within the kexec kernel after this change: [root@localhost ~]# cat /proc/iomem ... 140000000-33fffffff : Persistent Memory 140000000-1481fffff : namespace0.0 148200000-33fffffff : dax0.0 3280000000-32ffffffff : PCI Bus 0000:00 /sys/firmware/memmap/ before this change: 0000000000000000-000000000009fc00 (System RAM) 000000000009fc00-00000000000a0000 (Reserved) 00000000000f0000-0000000000100000 (Reserved) 0000000000100000-00000000bffdf000 (System RAM) 00000000bffdf000-00000000c0000000 (Reserved) 00000000feffc000-00000000ff000000 (Reserved) 00000000fffc0000-0000000100000000 (Reserved) 0000000100000000-0000000140000000 (System RAM) 0000000150000000-0000000340000000 (System RAM) /sys/firmware/memmap/ after a proper reboot: 0000000000000000-000000000009fc00 (System RAM) 000000000009fc00-00000000000a0000 (Reserved) 00000000000f0000-0000000000100000 (Reserved) 0000000000100000-00000000bffdf000 (System RAM) 00000000bffdf000-00000000c0000000 (Reserved) 00000000feffc000-00000000ff000000 (Reserved) 00000000fffc0000-0000000100000000 (Reserved) 0000000100000000-0000000140000000 (System RAM) /sys/firmware/memmap/ after this change: 0000000000000000-000000000009fc00 (System RAM) 000000000009fc00-00000000000a0000 (Reserved) 00000000000f0000-0000000000100000 (Reserved) 0000000000100000-00000000bffdf000 (System RAM) 00000000bffdf000-00000000c0000000 (Reserved) 00000000feffc000-00000000ff000000 (Reserved) 00000000fffc0000-0000000100000000 (Reserved) 0000000100000000-0000000140000000 (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 <akpm@linux-foundation.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com> Cc: Wei Yang <richard.weiyang@gmail.com> Cc: Baoquan He <bhe@redhat.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Eric Biederman <ebiederm@xmission.com> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> Cc: Dan Williams <dan.j.williams@intel.com> Signed-off-by: David Hildenbrand <david@redhat.com> --- drivers/dax/kmem.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)