mce: fix set_mce_nospec to always unmap the whole page

[ Upstream commit 5898b43af954b83c4a4ee4ab85c4dbafa395822a ]

The set_memory_uc() approach doesn't work well in all cases.
As Dan pointed out when "The VMM unmapped the bad page from
guest physical space and passed the machine check to the guest."
"The guest gets virtual #MC on an access to that page. When
the guest tries to do set_memory_uc() and instructs cpa_flush()
to do clean caches that results in taking another fault / exception
perhaps because the VMM unmapped the page from the guest."

Since the driver has special knowledge to handle NP or UC,
mark the poisoned page with NP and let driver handle it when
it comes down to repair.

Please refer to discussions here for more details.
https://lore.kernel.org/all/CAPcyv4hrXPb1tASBZUg-GgdVs0OOFKXMXLiHmktg_kFi7YBMyQ@mail.gmail.com/

Now since poisoned page is marked as not-present, in order to
avoid writing to a not-present page and trigger kernel Oops,
also fix pmem_do_write().

Fixes: 284ce4011ba6 ("x86/memory_failure: Introduce {set, clear}_mce_nospec()")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Jane Chu <jane.chu@oracle.com>
Acked-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/165272615484.103830.2563950688772226611.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 2d719e0d2e404bda8f8c650d075dcacb706a0416..9ed616e7e1cfacbadd73af17862e3d75fb9beaf5 100644 (file)
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -613,7 +613,7 @@ static int uc_decode_notifier(struct notifier_block *nb, unsigned long val,
 
        pfn = mce->addr >> PAGE_SHIFT;
        if (!memory_failure(pfn, 0)) {
-               set_mce_nospec(pfn, whole_page(mce));
+               set_mce_nospec(pfn);
                mce->kflags |= MCE_HANDLED_UC;
        }
 
@@ -1350,7 +1350,7 @@ static void kill_me_maybe(struct callback_head *cb)
 
        ret = memory_failure(p->mce_addr >> PAGE_SHIFT, flags);
        if (!ret) {
-               set_mce_nospec(p->mce_addr >> PAGE_SHIFT, p->mce_whole_page);
+               set_mce_nospec(p->mce_addr >> PAGE_SHIFT);
                sync_core();
                return;
        }
@@ -1374,7 +1374,7 @@ static void kill_me_never(struct callback_head *cb)
        p->mce_count = 0;
        pr_err("Kernel accessed poison in user space at %llx\n", p->mce_addr);
        if (!memory_failure(p->mce_addr >> PAGE_SHIFT, 0))
-               set_mce_nospec(p->mce_addr >> PAGE_SHIFT, p->mce_whole_page);
+               set_mce_nospec(p->mce_addr >> PAGE_SHIFT);
 }
 
 static void queue_task_work(struct mce *m, char *msg, void (*func)(struct callback_head *))

diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index b143972885eb344aec0a1ad4e80efd015f8bacce..1f1018104488948a0de244e0461eab484afdb5f2 100644 (file)
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -1925,14 +1925,9 @@ int set_memory_wb(unsigned long addr, int numpages)
 }
 EXPORT_SYMBOL(set_memory_wb);
 
-/*
- * Prevent speculative access to the page by either unmapping
- * it (if we do not require access to any part of the page) or
- * marking it uncacheable (if we want to try to retrieve data
- * from non-poisoned lines in the page).
- */
+/* Prevent speculative access to a page by marking it not-present */
 #ifdef CONFIG_X86_64
-int set_mce_nospec(unsigned long pfn, bool unmap)
+int set_mce_nospec(unsigned long pfn)
 {
        unsigned long decoy_addr;
        int rc;
@@ -1954,19 +1949,23 @@ int set_mce_nospec(unsigned long pfn, bool unmap)
         */
        decoy_addr = (pfn << PAGE_SHIFT) + (PAGE_OFFSET ^ BIT(63));
 
-       if (unmap)
-               rc = set_memory_np(decoy_addr, 1);
-       else
-               rc = set_memory_uc(decoy_addr, 1);
+       rc = set_memory_np(decoy_addr, 1);
        if (rc)
                pr_warn("Could not invalidate pfn=0x%lx from 1:1 map\n", pfn);
        return rc;
 }
 
+static int set_memory_present(unsigned long *addr, int numpages)
+{
+       return change_page_attr_set(addr, numpages, __pgprot(_PAGE_PRESENT), 0);
+}
+
 /* Restore full speculative operation to the pfn. */
 int clear_mce_nospec(unsigned long pfn)
 {
-       return set_memory_wb((unsigned long) pfn_to_kaddr(pfn), 1);
+       unsigned long addr = (unsigned long) pfn_to_kaddr(pfn);
+
+       return set_memory_present(&addr, 1);
 }
 EXPORT_SYMBOL_GPL(clear_mce_nospec);
 #endif /* CONFIG_X86_64 */

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 58d95242a836b07e45d71c8aea8a141bf68511a4..4aa17132a5572d0f862e5bbbad359d5d4c2263cf 100644 (file)
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -158,36 +158,20 @@ static blk_status_t pmem_do_write(struct pmem_device *pmem,
                        struct page *page, unsigned int page_off,
                        sector_t sector, unsigned int len)
 {
-       blk_status_t rc = BLK_STS_OK;
-       bool bad_pmem = false;
        phys_addr_t pmem_off = sector * 512 + pmem->data_offset;
        void *pmem_addr = pmem->virt_addr + pmem_off;
 
-       if (unlikely(is_bad_pmem(&pmem->bb, sector, len)))
-               bad_pmem = true;
+       if (unlikely(is_bad_pmem(&pmem->bb, sector, len))) {
+               blk_status_t rc = pmem_clear_poison(pmem, pmem_off, len);
+
+               if (rc != BLK_STS_OK)
+                       return rc;
+       }
 
-       /*
-        * Note that we write the data both before and after
-        * clearing poison.  The write before clear poison
-        * handles situations where the latest written data is
-        * preserved and the clear poison operation simply marks
-        * the address range as valid without changing the data.
-        * In this case application software can assume that an
-        * interrupted write will either return the new good
-        * data or an error.
-        *
-        * However, if pmem_clear_poison() leaves the data in an
-        * indeterminate state we need to perform the write
-        * after clear poison.
-        */
        flush_dcache_page(page);
        write_pmem(pmem_addr, page, page_off, len);
-       if (unlikely(bad_pmem)) {
-               rc = pmem_clear_poison(pmem, pmem_off, len);
-               write_pmem(pmem_addr, page, page_off, len);
-       }
 
-       return rc;
+       return BLK_STS_OK;
 }
 
 static void pmem_submit_bio(struct bio *bio)

diff --git a/include/linux/set_memory.h b/include/linux/set_memory.h
index 683a6c3f7179bb55b689d59b5e5382abfc6aeaa8..369769ce7399d7e31b4252ebbaf13f97647b960a 100644 (file)
--- a/include/linux/set_memory.h
+++ b/include/linux/set_memory.h
@@ -43,10 +43,10 @@ static inline bool can_set_direct_map(void)
 #endif /* CONFIG_ARCH_HAS_SET_DIRECT_MAP */
 
 #ifdef CONFIG_X86_64
-int set_mce_nospec(unsigned long pfn, bool unmap);
+int set_mce_nospec(unsigned long pfn);
 int clear_mce_nospec(unsigned long pfn);
 #else
-static inline int set_mce_nospec(unsigned long pfn, bool unmap)
+static inline int set_mce_nospec(unsigned long pfn)
 {
        return 0;
 }