linux-kernel - Re: [PATCH 3/3] x86, ras: Add mcsafe_memcpy() function to recover from machine checks

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Message-ID: <20151112075313.GA5984@gmail.com>
Date:	Thu, 12 Nov 2015 08:53:13 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Tony Luck <tony.luck@...el.com>
Cc:	Borislav Petkov <bp@...en8.de>, linux-kernel@...r.kernel.org,
	linux-edac@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH 3/3] x86, ras: Add mcsafe_memcpy() function to recover
 from machine checks


* Tony Luck <tony.luck@...el.com> 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.
> 
> Notes:
> 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?

Thanks,

	Ingo
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