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Date: Wed, 2 Mar 2016 12:47:41 -0800 From: "Luck, Tony" <tony.luck@...el.com> To: Ingo Molnar <mingo@...nel.org> Cc: linux-kernel@...r.kernel.org, Linus Torvalds <torvalds@...ux-foundation.org>, Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>, Andrew Morton <akpm@...ux-foundation.org>, Tony Luck <tony.luck@...il.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, "H. Peter Anvin" <hpa@...or.com>, Andy Lutomirski <luto@...capital.net> Subject: Re: [PATCH v14] x86, mce: Add memcpy_mcsafe() On Thu, Feb 18, 2016 at 11:47:26AM -0800, Tony Luck wrote: > Make use of the EXTABLE_FAULT exception table entries to write > a kernel copy routine that doesn't crash the system if it > encounters a machine check. Prime use case for this is to copy > from large arrays of non-volatile memory used as storage. > > We have to use an unrolled copy loop for now because current > hardware implementations treat a machine check in "rep mov" > as fatal. When that is fixed we can simplify. Ping. Anything more needed for this? In his last message Linus seemed OK with a *kernel* copy function that avoided death by machine check. He said: What a "memcpy_fault()" (or whatever it would be called) means is that the kernel is doing its own copies, but knows that there is some fragility involved, and wants to have a recovery mechanism that isn't "oops, we got a machine check in the kernel, now we need to kill the machine". The only things left to argue are the name, and the return value. -Tony
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