On Wed, 22 Dec 2010 10:51:55 +0800
Huang Ying <ying.huang@xxxxxxxxx> wrote:
> Make __get_user_pages return -EHWPOISON for HWPOISON page only if
> FOLL_HWPOISON is specified. With this patch, the interested callers
> can distinguish HWPOISON page from general FAULT page, while other
> callers will still get -EFAULT for pages, so the user space interface
> need not to be changed.
>
> get_user_pages_hwpoison is added as a variant of get_user_pages that
> can return -EHWPOISON for HWPOISON page.
>
> This feature is needed by KVM, where UCR MCE should be relayed to
> guest for HWPOISON page, while instruction emulation and MMIO will be
> tried for general FAULT page.
>
> The idea comes from Andrew Morton.
hm, I don't remember that. I suspect it came from someone else?
> Signed-off-by: Huang Ying <ying.huang@xxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> ---
> include/asm-generic/errno.h | 2 +
> include/linux/mm.h | 5 ++++
> mm/memory.c | 53 +++++++++++++++++++++++++++++++++++++++++---
> 3 files changed, 57 insertions(+), 3 deletions(-)
>
> --- a/include/asm-generic/errno.h
> +++ b/include/asm-generic/errno.h
> @@ -108,4 +108,6 @@
>
> #define ERFKILL 132 /* Operation not possible due to RF-kill */
>
> +#define EHWPOISON 133 /* Memory page has hardware error */
So this can be propagated to userspace?
If so, which syscalls might return EHWPOISON and are there any manpage
implications?
> #endif
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -860,6 +860,10 @@ int get_user_pages(struct task_struct *t
> struct page **pages, struct vm_area_struct **vmas);
> int get_user_pages_fast(unsigned long start, int nr_pages, int write,
> struct page **pages);
> +int get_user_pages_hwpoison(struct task_struct *tsk, struct mm_struct *mm,
> + unsigned long start, int nr_pages, int write,
> + int force, struct page **pages,
> + struct vm_area_struct **vmas);
> struct page *get_dump_page(unsigned long addr);
>
> extern int try_to_release_page(struct page * page, gfp_t gfp_mask);
> @@ -1415,6 +1419,7 @@ struct page *follow_page(struct vm_area_
> #define FOLL_GET 0x04 /* do get_page on page */
> #define FOLL_DUMP 0x08 /* give error on hole if it would be zero */
> #define FOLL_FORCE 0x10 /* get_user_pages read/write w/o permission */
> +#define FOLL_HWPOISON 0x20 /* check page is hwpoisoned */
>
> typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, unsigned long addr,
> void *data);
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1449,9 +1449,16 @@ int __get_user_pages(struct task_struct
> if (ret & VM_FAULT_ERROR) {
> if (ret & VM_FAULT_OOM)
> return i ? i : -ENOMEM;
> - if (ret &
> - (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE|
> - VM_FAULT_SIGBUS))
> + if (ret & (VM_FAULT_HWPOISON |
> + VM_FAULT_HWPOISON_LARGE)) {
> + if (i)
> + return i;
> + else if (gup_flags & FOLL_HWPOISON)
> + return -EHWPOISON;
> + else
> + return -EFAULT;
> + }
> + if (ret & VM_FAULT_SIGBUS)
hm, that function is getting a bit unweildy.
> /**
> + * get_user_pages_hwpoison() - pin user pages in memory, return hwpoison status
> + * @tsk: task_struct of target task
> + * @mm: mm_struct of target mm
> + * @start: starting user address
> + * @nr_pages: number of pages from start to pin
> + * @write: whether pages will be written to by the caller
> + * @force: whether to force write access even if user mapping is
> + * readonly. This will result in the page being COWed even
> + * in MAP_SHARED mappings. You do not want this.
> + * @pages: array that receives pointers to the pages pinned.
> + * Should be at least nr_pages long. Or NULL, if caller
> + * only intends to ensure the pages are faulted in.
> + * @vmas: array of pointers to vmas corresponding to each page.
> + * Or NULL if the caller does not require them.
> + *
> + * Returns number of pages pinned.
> + *
> + * If the page table or memory page is hwpoisoned, return -EHWPOISON.
> + *
> + * Otherwise, same as get_user_pages.
> + */
> +int get_user_pages_hwpoison(struct task_struct *tsk, struct mm_struct *mm,
> + unsigned long start, int nr_pages, int write,
> + int force, struct page **pages,
> + struct vm_area_struct **vmas)
> +{
> + int flags = FOLL_TOUCH | FOLL_HWPOISON;
> +
> + if (pages)
> + flags |= FOLL_GET;
> + if (write)
> + flags |= FOLL_WRITE;
> + if (force)
> + flags |= FOLL_FORCE;
> +
> + return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas);
> +}
> +EXPORT_SYMBOL(get_user_pages_hwpoison);
Seems that this patch will add unused bloat for CONFIG_PAGE_POISONING=n
kernels?
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