Messages in this thread | | | Subject | Re: [PATCH v4 10/10] x86/xsaves: Re-enable XSAVES | From | Dave Hansen <> | Date | Wed, 4 May 2016 15:41:49 -0700 |
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It's my fault, but you also need to go update
fpu__xfeature_set_state() and __raw_xsave_addr()
The theoretical problem is that you might ask for a __raw_xsave_addr() of a component which has been compacted out of an XSAVES buffer and thus has no address. We could work around this by doing a memmove() and moving the components "up" after the one we are trying to set in order to make space.
But, since we *always* call XSAVES with an instruction mask of -1 and end up with a requested feature bitmap (RFBM) equal to XCR0, I think we can do a shortcut because we'll practically *always* have an xcomp_bv==RFBM==XCR0, which means that all (present) components will always have an address.
So, the alternative to doing the memmove() is to add some WARN_ON_FPU() checks to enforce xcomp_bv==RFBM==XCR0 in places where we call XSAVES/XRSTORS and __raw_xsave_addr(), maybe more.
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