On Thu, Dec 10, 2015 at 04:21:50PM -0800, Tony Luck 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() > 3) Provide helpful macros to decode the return value. > > Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx> > --- > arch/x86/include/asm/uaccess_64.h | 5 +++ > arch/x86/kernel/x8664_ksyms_64.c | 2 + > arch/x86/lib/copy_user_64.S | 91 +++++++++++++++++++++++++++++++++++++++ > 3 files changed, 98 insertions(+) ... > + * mcsafe_memcpy - Uncached memory copy with machine check exception handling > + * Note that we only catch machine checks when reading the source addresses. > + * Writes to target are posted and don't generate machine checks. > + * This will force destination/source out of cache for more performance. ... and the non-temporal version is the optimal one even though we're defaulting to copy_user_enhanced_fast_string for memcpy on modern Intel CPUs...? Btw, it should be also inside an ifdef if we're going to ifdef CONFIG_MCE_KERNEL_RECOVERY everywhere else. -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>