Merge tag 'libnvdimm-for-4.19_dax-memory-failure' of gitolite.kernel.org:pub/scm/linux/kernel/git/nvdimm/nvdimm

Pull libnvdimm memory-failure update from Dave Jiang:
 "As it stands, memory_failure() gets thoroughly confused by dev_pagemap
  backed mappings. The recovery code has specific enabling for several
  possible page states and needs new enabling to handle poison in dax
  mappings.

  In order to support reliable reverse mapping of user space addresses:

   1/ Add new locking in the memory_failure() rmap path to prevent races
      that would typically be handled by the page lock.

   2/ Since dev_pagemap pages are hidden from the page allocator and the
      "compound page" accounting machinery, add a mechanism to determine
      the size of the mapping that encompasses a given poisoned pfn.

   3/ Given pmem errors can be repaired, change the speculatively
      accessed poison protection, mce_unmap_kpfn(), to be reversible and
      otherwise allow ongoing access from the kernel.

  A side effect of this enabling is that MADV_HWPOISON becomes usable
  for dax mappings, however the primary motivation is to allow the
  system to survive userspace consumption of hardware-poison via dax.
  Specifically the current behavior is:

     mce: Uncorrected hardware memory error in user-access at af34214200
     {1}[Hardware Error]: It has been corrected by h/w and requires no further action
     mce: [Hardware Error]: Machine check events logged
     {1}[Hardware Error]: event severity: corrected
     Memory failure: 0xaf34214: reserved kernel page still referenced by 1 users
     [..]
     Memory failure: 0xaf34214: recovery action for reserved kernel page: Failed
     mce: Memory error not recovered
     <reboot>

  ...and with these changes:

     Injecting memory failure for pfn 0x20cb00 at process virtual address 0x7f763dd00000
     Memory failure: 0x20cb00: Killing dax-pmd:5421 due to hardware memory corruption
     Memory failure: 0x20cb00: recovery action for dax page: Recovered

  Given all the cross dependencies I propose taking this through
  nvdimm.git with acks from Naoya, x86/core, x86/RAS, and of course dax
  folks"

* tag 'libnvdimm-for-4.19_dax-memory-failure' of gitolite.kernel.org:pub/scm/linux/kernel/git/nvdimm/nvdimm:
  libnvdimm, pmem: Restore page attributes when clearing errors
  x86/memory_failure: Introduce {set, clear}_mce_nospec()
  x86/mm/pat: Prepare {reserve, free}_memtype() for "decoy" addresses
  mm, memory_failure: Teach memory_failure() about dev_pagemap pages
  filesystem-dax: Introduce dax_lock_mapping_entry()
  mm, memory_failure: Collect mapping size in collect_procs()
  mm, madvise_inject_error: Let memory_failure() optionally take a page reference
  mm, dev_pagemap: Do not clear ->mapping on final put
  mm, madvise_inject_error: Disable MADV_SOFT_OFFLINE for ZONE_DEVICE pages
  filesystem-dax: Set page->index
  device-dax: Set page->index
  device-dax: Enable page_mapping()
  device-dax: Convert to vmf_insert_mixed and vm_fault_t

2 files changed, 3 insertions, 50 deletions

diff --git a/arch/x86/kernel/cpu/mcheck/mce-internal.h b/arch/x86/kernel/cpu/mcheck/mce-internal.h
index 374d1aa66952..ceb67cd5918f 100644
--- a/arch/x86/kernel/cpu/mcheck/mce-internal.h
+++ b/arch/x86/kernel/cpu/mcheck/mce-internal.h
@@ -113,21 +113,6 @@ static inline void mce_register_injector_chain(struct notifier_block *nb)	{ }
 static inline void mce_unregister_injector_chain(struct notifier_block *nb)	{ }
 #endif
 
-#ifndef CONFIG_X86_64
-/*
- * On 32-bit systems it would be difficult to safely unmap a poison page
- * from the kernel 1:1 map because there are no non-canonical addresses that
- * we can use to refer to the address without risking a speculative access.
- * However, this isn't much of an issue because:
- * 1) Few unmappable pages are in the 1:1 map. Most are in HIGHMEM which
- *    are only mapped into the kernel as needed
- * 2) Few people would run a 32-bit kernel on a machine that supports
- *    recoverable errors because they have too much memory to boot 32-bit.
- */
-static inline void mce_unmap_kpfn(unsigned long pfn) {}
-#define mce_unmap_kpfn mce_unmap_kpfn
-#endif
-
 struct mca_config {
 	bool dont_log_ce;
 	bool cmci_disabled;
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 4b767284b7f5..953b3ce92dcc 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -42,6 +42,7 @@
 #include <linux/irq_work.h>
 #include <linux/export.h>
 #include <linux/jump_label.h>
+#include <linux/set_memory.h>
 
 #include <asm/intel-family.h>
 #include <asm/processor.h>
@@ -50,7 +51,6 @@
 #include <asm/mce.h>
 #include <asm/msr.h>
 #include <asm/reboot.h>
-#include <asm/set_memory.h>
 
 #include "mce-internal.h"
 
@@ -108,10 +108,6 @@ static struct irq_work mce_irq_work;
 
 static void (*quirk_no_way_out)(int bank, struct mce *m, struct pt_regs *regs);
 
-#ifndef mce_unmap_kpfn
-static void mce_unmap_kpfn(unsigned long pfn);
-#endif
-
 /*
  * CPU/chipset specific EDAC code can register a notifier call here to print
  * MCE errors in a human-readable form.
@@ -602,7 +598,7 @@ static int srao_decode_notifier(struct notifier_block *nb, unsigned long val,
 	if (mce_usable_address(mce) && (mce->severity == MCE_AO_SEVERITY)) {
 		pfn = mce->addr >> PAGE_SHIFT;
 		if (!memory_failure(pfn, 0))
-			mce_unmap_kpfn(pfn);
+			set_mce_nospec(pfn);
 	}
 
 	return NOTIFY_OK;
@@ -1072,38 +1068,10 @@ static int do_memory_failure(struct mce *m)
 	if (ret)
 		pr_err("Memory error not recovered");
 	else
-		mce_unmap_kpfn(m->addr >> PAGE_SHIFT);
+		set_mce_nospec(m->addr >> PAGE_SHIFT);
 	return ret;
 }
 
-#ifndef mce_unmap_kpfn
-static void mce_unmap_kpfn(unsigned long pfn)
-{
-	unsigned long decoy_addr;
-
-	/*
-	 * Unmap this page from the kernel 1:1 mappings to make sure
-	 * we don't log more errors because of speculative access to
-	 * the page.
-	 * We would like to just call:
-	 *	set_memory_np((unsigned long)pfn_to_kaddr(pfn), 1);
-	 * but doing that would radically increase the odds of a
-	 * speculative access to the poison page because we'd have
-	 * the virtual address of the kernel 1:1 mapping sitting
-	 * around in registers.
-	 * Instead we get tricky.  We create a non-canonical address
-	 * that looks just like the one we want, but has bit 63 flipped.
-	 * This relies on set_memory_np() not checking whether we passed
-	 * a legal address.
-	 */
-
-	decoy_addr = (pfn << PAGE_SHIFT) + (PAGE_OFFSET ^ BIT(63));
-
-	if (set_memory_np(decoy_addr, 1))
-		pr_warn("Could not invalidate pfn=0x%lx from 1:1 map\n", pfn);
-}
-#endif
-
 
 /*
  * Cases where we avoid rendezvous handler timeout: