--- /dev/null
+From 956a4cd2c957acf638ff29951aabaa9d8e92bbc2 Mon Sep 17 00:00:00 2001
+From: Dan Williams <dan.j.williams@intel.com>
+Date: Fri, 7 Apr 2017 16:42:08 -0700
+Subject: device-dax: switch to srcu, fix rcu_read_lock() vs pte allocation
+
+From: Dan Williams <dan.j.williams@intel.com>
+
+commit 956a4cd2c957acf638ff29951aabaa9d8e92bbc2 upstream.
+
+The following warning triggers with a new unit test that stresses the
+device-dax interface.
+
+ ===============================
+ [ ERR: suspicious RCU usage. ]
+ 4.11.0-rc4+ #1049 Tainted: G O
+ -------------------------------
+ ./include/linux/rcupdate.h:521 Illegal context switch in RCU read-side critical section!
+
+ other info that might help us debug this:
+
+ rcu_scheduler_active = 2, debug_locks = 0
+ 2 locks held by fio/9070:
+ #0: (&mm->mmap_sem){++++++}, at: [<ffffffff8d0739d7>] __do_page_fault+0x167/0x4f0
+ #1: (rcu_read_lock){......}, at: [<ffffffffc03fbd02>] dax_dev_huge_fault+0x32/0x620 [dax]
+
+ Call Trace:
+ dump_stack+0x86/0xc3
+ lockdep_rcu_suspicious+0xd7/0x110
+ ___might_sleep+0xac/0x250
+ __might_sleep+0x4a/0x80
+ __alloc_pages_nodemask+0x23a/0x360
+ alloc_pages_current+0xa1/0x1f0
+ pte_alloc_one+0x17/0x80
+ __pte_alloc+0x1e/0x120
+ __get_locked_pte+0x1bf/0x1d0
+ insert_pfn.isra.70+0x3a/0x100
+ ? lookup_memtype+0xa6/0xd0
+ vm_insert_mixed+0x64/0x90
+ dax_dev_huge_fault+0x520/0x620 [dax]
+ ? dax_dev_huge_fault+0x32/0x620 [dax]
+ dax_dev_fault+0x10/0x20 [dax]
+ __do_fault+0x1e/0x140
+ __handle_mm_fault+0x9af/0x10d0
+ handle_mm_fault+0x16d/0x370
+ ? handle_mm_fault+0x47/0x370
+ __do_page_fault+0x28c/0x4f0
+ trace_do_page_fault+0x58/0x2a0
+ do_async_page_fault+0x1a/0xa0
+ async_page_fault+0x28/0x30
+
+Inserting a page table entry may trigger an allocation while we are
+holding a read lock to keep the device instance alive for the duration
+of the fault. Use srcu for this keep-alive protection.
+
+Fixes: dee410792419 ("/dev/dax, core: file operations and dax-mmap")
+Signed-off-by: Dan Williams <dan.j.williams@intel.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ drivers/dax/Kconfig | 1 +
+ drivers/dax/dax.c | 13 +++++++------
+ 2 files changed, 8 insertions(+), 6 deletions(-)
+
+--- a/drivers/dax/Kconfig
++++ b/drivers/dax/Kconfig
+@@ -2,6 +2,7 @@ menuconfig DEV_DAX
+ tristate "DAX: direct access to differentiated memory"
+ default m if NVDIMM_DAX
+ depends on TRANSPARENT_HUGEPAGE
++ select SRCU
+ help
+ Support raw access to differentiated (persistence, bandwidth,
+ latency...) memory via an mmap(2) capable character
+--- a/drivers/dax/dax.c
++++ b/drivers/dax/dax.c
+@@ -24,6 +24,7 @@
+ #include "dax.h"
+
+ static dev_t dax_devt;
++DEFINE_STATIC_SRCU(dax_srcu);
+ static struct class *dax_class;
+ static DEFINE_IDA(dax_minor_ida);
+ static int nr_dax = CONFIG_NR_DEV_DAX;
+@@ -59,7 +60,7 @@ struct dax_region {
+ * @region - parent region
+ * @dev - device backing the character device
+ * @cdev - core chardev data
+- * @alive - !alive + rcu grace period == no new mappings can be established
++ * @alive - !alive + srcu grace period == no new mappings can be established
+ * @id - child id in the region
+ * @num_resources - number of physical address extents in this device
+ * @res - array of physical address ranges
+@@ -530,7 +531,7 @@ static int __dax_dev_pmd_fault(struct da
+ static int dax_dev_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
+ pmd_t *pmd, unsigned int flags)
+ {
+- int rc;
++ int rc, id;
+ struct file *filp = vma->vm_file;
+ struct dax_dev *dax_dev = filp->private_data;
+
+@@ -538,9 +539,9 @@ static int dax_dev_pmd_fault(struct vm_a
+ current->comm, (flags & FAULT_FLAG_WRITE)
+ ? "write" : "read", vma->vm_start, vma->vm_end);
+
+- rcu_read_lock();
++ id = srcu_read_lock(&dax_srcu);
+ rc = __dax_dev_pmd_fault(dax_dev, vma, addr, pmd, flags);
+- rcu_read_unlock();
++ srcu_read_unlock(&dax_srcu, id);
+
+ return rc;
+ }
+@@ -656,11 +657,11 @@ static void unregister_dax_dev(void *dev
+ * Note, rcu is not protecting the liveness of dax_dev, rcu is
+ * ensuring that any fault handlers that might have seen
+ * dax_dev->alive == true, have completed. Any fault handlers
+- * that start after synchronize_rcu() has started will abort
++ * that start after synchronize_srcu() has started will abort
+ * upon seeing dax_dev->alive == false.
+ */
+ dax_dev->alive = false;
+- synchronize_rcu();
++ synchronize_srcu(&dax_srcu);
+ unmap_mapping_range(dax_dev->inode->i_mapping, 0, 0, 1);
+ cdev_del(cdev);
+ device_unregister(dev);
--- /dev/null
+From 29f72ce3e4d18066ec75c79c857bee0618a3504b Mon Sep 17 00:00:00 2001
+From: Yazen Ghannam <yazen.ghannam@amd.com>
+Date: Thu, 30 Mar 2017 13:17:14 +0200
+Subject: x86/mce/AMD: Give a name to MCA bank 3 when accessed with legacy MSRs
+
+From: Yazen Ghannam <yazen.ghannam@amd.com>
+
+commit 29f72ce3e4d18066ec75c79c857bee0618a3504b upstream.
+
+MCA bank 3 is reserved on systems pre-Fam17h, so it didn't have a name.
+However, MCA bank 3 is defined on Fam17h systems and can be accessed
+using legacy MSRs. Without a name we get a stack trace on Fam17h systems
+when trying to register sysfs files for bank 3 on kernels that don't
+recognize Scalable MCA.
+
+Call MCA bank 3 "decode_unit" since this is what it represents on
+Fam17h. This will allow kernels without SMCA support to see this bank on
+Fam17h+ and prevent the stack trace. This will not affect older systems
+since this bank is reserved on them, i.e. it'll be ignored.
+
+Tested on AMD Fam15h and Fam17h systems.
+
+ WARNING: CPU: 26 PID: 1 at lib/kobject.c:210 kobject_add_internal
+ kobject: (ffff88085bb256c0): attempted to be registered with empty name!
+ ...
+ Call Trace:
+ kobject_add_internal
+ kobject_add
+ kobject_create_and_add
+ threshold_create_device
+ threshold_init_device
+
+Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
+Signed-off-by: Borislav Petkov <bp@suse.de>
+Link: http://lkml.kernel.org/r/1490102285-3659-1-git-send-email-Yazen.Ghannam@amd.com
+Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ arch/x86/kernel/cpu/mcheck/mce_amd.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+--- a/arch/x86/kernel/cpu/mcheck/mce_amd.c
++++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c
+@@ -60,7 +60,7 @@ static const char * const th_names[] = {
+ "load_store",
+ "insn_fetch",
+ "combined_unit",
+- "",
++ "decode_unit",
+ "northbridge",
+ "execution_unit",
+ };
projects / thirdparty / kernel / stable-queue.git / commitdiff
