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Subject: Re: [PATCH 1/2] mm, Make __get_user_pages return -EHWPOISON for
 HWPOISON page optionally
From: Huang Ying <ying.huang@intel.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>,
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        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        Andi Kleen <andi@firstfloor.org>, "Luck, Tony" <tony.luck@intel.com>,
        Dean Nelson <dnelson@redhat.com>
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Date: Mon, 17 Jan 2011 08:47:39 +0800
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Hi, Andrew,

On Sun, 2011-01-16 at 23:35 +0800, Avi Kivity wrote:
> On 01/14/2011 03:37 AM, Huang Ying wrote:
> > On Thu, 2011-01-13 at 18:43 +0800, Avi Kivity wrote:
> > >  On 01/13/2011 10:42 AM, Huang Ying 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.
> > >  >
> > >  >  Signed-off-by: Huang Ying<ying.huang@intel.com>
> > >  >  Cc: Andrew Morton<akpm@linux-foundation.org>
> > >  >
> > >  >  +#ifdef CONFIG_MEMORY_FAILURE
> > >  >  +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);
> > >  >  +#else
> > >
> > >  Since we'd also like to add get_user_pages_noio(), perhaps adding a
> > >  flags field to get_user_pages() is better.
> >
> > Or export __get_user_pages()?
> 
> That's better, yes.

Do you think it is a good idea to export __get_user_pages() instead of
adding get_user_pages_noio() and get_user_pages_hwpoison()?

Best Regards,
Huang Ying