On Fri, Jun 08, 2018 at 04:51:19PM -0700, Dan Williams wrote:
> 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
>
> In contrast to typical memory, dev_pagemap pages may be dax mapped. With
> dax there is no possibility to map in another page dynamically since dax
> establishes 1:1 physical address to file offset associations. Also
> dev_pagemap pages associated with NVDIMM / persistent memory devices can
> internal remap/repair addresses with poison. While memory_failure()
> assumes that it can discard typical poisoned pages and keep them
> unmapped indefinitely, dev_pagemap pages may be returned to service
> after the error is cleared.
>
> Teach memory_failure() to detect and handle MEMORY_DEVICE_HOST
> dev_pagemap pages that have poison consumed by userspace. Mark the
> memory as UC instead of unmapping it completely to allow ongoing access
> via the device driver (nd_pmem). Later, nd_pmem will grow support for
> marking the page back to WB when the error is cleared.
>
> Cc: Jan Kara <jack@xxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: Jérôme Glisse <jglisse@xxxxxxxxxx>
> Cc: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
> Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
> Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> ---
<>
> +static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
> + struct dev_pagemap *pgmap)
> +{
> + const bool unmap_success = true;
> + unsigned long size;
> + struct page *page;
> + LIST_HEAD(tokill);
> + int rc = -EBUSY;
> + loff_t start;
> +
> + /*
> + * Prevent the inode from being freed while we are interrogating
> + * the address_space, typically this would be handled by
> + * lock_page(), but dax pages do not use the page lock.
> + */
> + page = dax_lock_page(pfn);
> + if (!page)
> + goto out;
> +
> + if (hwpoison_filter(page)) {
> + rc = 0;
> + goto unlock;
> + }
> +
> + switch (pgmap->type) {
> + case MEMORY_DEVICE_PRIVATE:
> + case MEMORY_DEVICE_PUBLIC:
> + /*
> + * TODO: Handle HMM pages which may need coordination
> + * with device-side memory.
> + */
> + goto unlock;
> + default:
> + break;
> + }
> +
> + /*
> + * If the page is not mapped in userspace then report it as
> + * unhandled.
> + */
> + size = dax_mapping_size(page);
> + if (!size) {
> + pr_err("Memory failure: %#lx: failed to unmap page\n", pfn);
> + goto unlock;
> + }
> +
> + SetPageHWPoison(page);
> +
> + /*
> + * Unlike System-RAM there is no possibility to swap in a
> + * different physical page at a given virtual address, so all
> + * userspace consumption of ZONE_DEVICE memory necessitates
> + * SIGBUS (i.e. MF_MUST_KILL)
> + */
> + flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;
> + collect_procs(page, &tokill, flags & MF_ACTION_REQUIRED);
You know "flags & MF_ACTION_REQUIRED" will always be true, so you can just
pass in MF_ACTION_REQUIRED or even just "true".
> +
> + start = (page->index << PAGE_SHIFT) & ~(size - 1);
> + unmap_mapping_range(page->mapping, start, start + size, 0);
> +
> + kill_procs(&tokill, flags & MF_MUST_KILL, !unmap_success, ilog2(size),
You know "flags & MF_MUST_KILL" will always be true, so you can just pass in
MF_MUST_KILL or even just "true".
Also, you can get rid of the constant "unmap_success" if you want and just
pass in false as the 3rd argument.
