On 07/19/17 16:33, H. Peter Anvin wrote: >> >> I agree that it is odd but that's how the compiler generates code. I >> will re-explore PIC options with mcmodel=small or medium, as mentioned >> on other threads. > > Why should the way compiler generates code affect the way we do things > in assembly? > > That being said, the compiler now has support for generating this kind > of code explicitly via the __seg_gs pointer modifier. That should let > us drop the __percpu_prefix and just use variables directly. I suspect > we want to declare percpu variables as "volatile __seg_gs" to account > for the possibility of CPU switches. > > Older compilers won't be able to work with this, of course, but I think > that it is acceptable for those older compilers to not be able to > support PIE. >
Grump. It turns out that the compiler doesn't do the right thing for symbols marked with the __seg_[fg]s markers. __thread does the right thing, but __thread a) has %fs: hard-coded, still, and b) I believe can still cache %seg:0 arbitrarily long. -hpa _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel