powerpc/pseries: Verify CPU doesn't exist before adding
PATCH 1/1 powerpc/pseries: Verify CPU doesn't exist before adding
When DLPAR adding a CPU we should verify that the CPU does not already exist. Failure to do so can generate a kernel oops;
[ 9.465585] kernel BUG at arch/powerpc/platforms/pseries/dlpar.c:382! [ 9.465796] Oops: Exception in kernel mode, sig: 5 [#1]
This oops can be generated by causing a probe to be performed on a cpu by writing to the sysfs cpu probe file (/sys/devices/system/cpu/probe). This patch adds a check for the existence of cpu prior to probing the cpu so userspace doing the wrong thing won't trigger a BUG_ON().
--- arch/powerpc/platforms/pseries/dlpar.c | 43 +++++++++++++++++++++++++++++--- 1 file changed, 39 insertions(+), 4 deletions(-)
arch/powerpc/platforms/pseries/dlpar.c +39 -4
@@ -381,6 +381,32 @@ out: } +static bool dlpar_cpu_exists (struct device_node *parent,u32 drc_index) +{ +struct device_node *child =NULL ; +u32 my_drc_index; +bool found; +int rc; + +/* Assume cpu doesn't exist */ + found = false; + +for_each_child_of_node (parent, child) { + rc =of_property_read_u32 (child,"ibm,my-drc-index" , + &my_drc_index); +if (rc) +continue ; + +if (my_drc_index == drc_index) { +of_node_put (child); + found = true; +break ; + } + } + +return found; +} +static ssize_t dlpar_cpu_probe (const char *buf,size_t count) {struct device_node *dn, *parent;
@@ -391,14 +417,23 @@ static ssize_t dlpar_cpu_probe(const char *buf, size_t count)if (rc)return -EINVAL ; - rc =dlpar_acquire_drc (drc_index); -if (rc) -return -EINVAL ; - parent =of_find_node_by_path ("/cpus" );if (!parent)return -ENODEV ; +if (dlpar_cpu_exists (parent, drc_index)) { +of_node_put (parent); +printk (KERN_WARNING "CPU with drc index %x already exists\n" , + drc_index); +return -EINVAL ; + } + + rc =dlpar_acquire_drc (drc_index); +if (rc) { +of_node_put (parent); +return -EINVAL ; + } + dn =dlpar_configure_connector (cpu_to_be32 (drc_index), parent);of_node_put (parent);if (!dn) {
Quoted 10 lines · Nathan Fontenot
When DLPAR adding a CPU we should verify that the CPU does not already exist. Failure to do so can generate a kernel oops;
[ 9.465585] kernel BUG at arch/powerpc/platforms/pseries/dlpar.c:382! [ 9.465796] Oops: Exception in kernel mode, sig: 5 [#1]This oops can be generated by causing a probe to be performed on a cpu by writing to the sysfs cpu probe file (
/sys/devices/system/cpu/probe). This patch adds a check for the existence of cpu prior to probing the cpu so userspace doing the wrong thing won't trigger aBUG_ON().
Hi Nathan,
Can you please tell how to trigger the oops manually since I've tried to write a core number to the probe file, but with no luck. Always get -EINVAL.
Thanks!
Quoted 79 lines
Signed-off-by Nathan Fontenot <[email protected]>--- arch/powerpc/platforms/pseries/dlpar.c | 43 +++++++++++++++++++++++++++++--- 1 file changed, 39 insertions(+), 4 deletions(-)arch/powerpc/platforms/pseries/dlpar.c +39
-4@@ -381,6 +381,32 @@ out: } +static bool dlpar_cpu_exists (struct device_node *parent,u32 drc_index) +{ +struct device_node *child =NULL ; +u32 my_drc_index; +bool found; +int rc; + +/* Assume cpu doesn't exist */ + found = false; + +for_each_child_of_node (parent, child) { + rc =of_property_read_u32 (child,"ibm,my-drc-index" , + &my_drc_index); +if (rc) +continue ; + +if (my_drc_index == drc_index) { +of_node_put (child); + found = true; +break ; + } + } + +return found; +} +static ssize_t dlpar_cpu_probe (const char *buf,size_t count) {struct device_node *dn, *parent;@@ -391,14 +417,23 @@ static ssize_t dlpar_cpu_probe(const char *buf, size_t count)if (rc)return -EINVAL ; - rc =dlpar_acquire_drc (drc_index); -if (rc) -return -EINVAL ; - parent =of_find_node_by_path ("/cpus" );if (!parent)return -ENODEV ; +if (dlpar_cpu_exists (parent, drc_index)) { +of_node_put (parent); +printk (KERN_WARNING "CPU with drc index %x already exists\n" , + drc_index); +return -EINVAL ; + } + + rc =dlpar_acquire_drc (drc_index); +if (rc) { +of_node_put (parent); +return -EINVAL ; + } + dn =dlpar_configure_connector (cpu_to_be32 (drc_index), parent);of_node_put (parent);if (!dn) {
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Quoted 12 lines · Denis Kirjanov
Quoted 10 lines · Nathan Fontenot
When DLPAR adding a CPU we should verify that the CPU does not already exist. Failure to do so can generate a kernel oops;
[ 9.465585] kernel BUG at arch/powerpc/platforms/pseries/dlpar.c:382! [ 9.465796] Oops: Exception in kernel mode, sig: 5 [#1]This oops can be generated by causing a probe to be performed on a cpu by writing to the sysfs cpu probe file (
/sys/devices/system/cpu/probe). This patch adds a check for the existence of cpu prior to probing the cpu so userspace doing the wrong thing won't trigger aBUG_ON().
Quoted 4 lines
Hi Nathan,
Can you please tell how to trigger the oops manually since I've tried to write a core number to the probe file, but with no luck. Always get
-EINVAL.
Triggering the oops manually may be a bit trickier than just writing to the sysfs file.
First, make sure you are writing the drc index of a cpu that is already present. You can see a list of present cpus with 'lsslot -c cpu'.
You may be able to trigger the oops by just writing the drc index to the sysfs file but will likely get -EINVAL since the probe code tries to acquire the cpu from firmware and call configure-connector, both of which will likely fail before we try to online the cpu and see the BUG_ON.
For a kvm guest, you should be able to generate the oops by killing the rtas_errd daemon, do a cpu hotplug add from the host, then reboot the guest. If the rtas_errd daemon is set to autostart you should see the oops at boot, otherwise you can manually start rtas_errd and see the oops.
For a Power LPAR, the process would be much trickier. You would have to do some hacking to the drmgr command (which write the drc index to the probe file) to trick it into trying to add the same cpu twice when invoking cpu hotplug from the HMC.
Hope that helps.
-Nathan
Quoted 82 lines
Thanks!
Quoted 79 lines
Signed-off-by Nathan Fontenot <[email protected]>--- arch/powerpc/platforms/pseries/dlpar.c | 43 +++++++++++++++++++++++++++++--- 1 file changed, 39 insertions(+), 4 deletions(-)arch/powerpc/platforms/pseries/dlpar.c +39
-4@@ -381,6 +381,32 @@ out: } +static bool dlpar_cpu_exists (struct device_node *parent,u32 drc_index) +{ +struct device_node *child =NULL ; +u32 my_drc_index; +bool found; +int rc; + +/* Assume cpu doesn't exist */ + found = false; + +for_each_child_of_node (parent, child) { + rc =of_property_read_u32 (child,"ibm,my-drc-index" , + &my_drc_index); +if (rc) +continue ; + +if (my_drc_index == drc_index) { +of_node_put (child); + found = true; +break ; + } + } + +return found; +} +static ssize_t dlpar_cpu_probe (const char *buf,size_t count) {struct device_node *dn, *parent;@@ -391,14 +417,23 @@ static ssize_t dlpar_cpu_probe(const char *buf, size_t count)if (rc)return -EINVAL ; - rc =dlpar_acquire_drc (drc_index); -if (rc) -return -EINVAL ; - parent =of_find_node_by_path ("/cpus" );if (!parent)return -ENODEV ; +if (dlpar_cpu_exists (parent, drc_index)) { +of_node_put (parent); +printk (KERN_WARNING "CPU with drc index %x already exists\n" , + drc_index); +return -EINVAL ; + } + + rc =dlpar_acquire_drc (drc_index); +if (rc) { +of_node_put (parent); +return -EINVAL ; + } + dn =dlpar_configure_connector (cpu_to_be32 (drc_index), parent);of_node_put (parent);if (!dn) {
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Quoted 6 lines · Nathan Fontenot
When DLPAR adding a CPU we should verify that the CPU does not already exist. Failure to do so can generate a kernel oops;
[ 9.465585] kernel BUG at arch/powerpc/platforms/pseries/dlpar.c:382! [ 9.465796] Oops: Exception in kernel mode, sig: 5 [#1]
Quoted 6 lines
This oops can be generated by causing a probe to be performed on a cpu by writing to the sysfs cpu probe file (
/sys/devices/system/cpu/probe). This patch adds a check for the existence of cpu prior to probing the cpu so userspace doing the wrong thing won't trigger aBUG_ON().Signed-off-by Nathan Fontenot <[email protected]>
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/1f859adb9253c2010799625822
cheers