On 01/23/2017 06:09 PM, Kevin Hao wrote: > On Mon, Jan 23, 2017 at 06:01:10PM -0800, Dave Hansen wrote: >> On 01/23/2017 05:50 PM, Kevin Hao wrote: >>> According to the ISA manual, XSAVES also set the XCOMP_BV[62:0]. My code only >>> try to be compatible with what the cpu does when excuting XSAVES. The following >>> is quoted from 325462-sdm-vol-1-2abcd-3abcd.pdf. >>> The XSAVES instructions sets bit 63 of the XCOMP_BV field of the XSAVE header while writing RFBM[62:0] to >>> XCOMP_BV[62:0]. The XSAVES instruction does not write any part of the XSAVE header other than the XSTATE_BV >>> and XCOMP_BV fields. >> What purpose does it serve to make copyin_to_xsaves() set that bit, > We try to fake up a memory area which is supposed to be composed by XSAVES > instruction. My code is just trying to do what the XSAVES do. No. copyin_to_xsaves() copies data into an *existing* XSAVES-formatted buffer. If you want to change what it does, fine, but that's not what it does or tries to do today. >> other than helping to hide bugs? > Why do you think it hide the bug? In contrast, I think my patch fixes what the > bug really is. The memory area we fake up is bug, we should fix it there. Yu-cheng found the bug. That bug will probably manifest in other code paths than copyin_to_xsaves(). If we did your patch, it would hide the bug in those other code paths. -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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