Re: [PATCH 3/3] x86, ras: Add mcsafe_memcpy() function to recover from machine checks
From: Ingo Molnar
Date: Thu Nov 12 2015 - 02:53:24 EST
* Tony Luck <tony.luck@xxxxxxxxx> wrote:
> Using __copy_user_nocache() as inspiration create a memory copy
> routine for use by kernel code with annotations to allow for
> recovery from machine checks.
> 1) Unlike the original we make no attempt to copy all the bytes
> up to the faulting address. The original achieves that by
> re-executing the failing part as a byte-by-byte copy,
> which will take another page fault. We don't want to have
> a second machine check!
> 2) Likewise the return value for the original indicates exactly
> how many bytes were not copied. Instead we provide the physical
> address of the fault (thanks to help from do_machine_check()
> +extern phys_addr_t mcsafe_memcpy(void *dst, const void __user *src,
> + unsigned size);
So what's the longer term purpose, where will mcsafe_memcpy() be used?
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