On Tue, Nov 23, 2021 at 10:11:33AM +0000, Marc Zyngier wrote: > Mark Brown <broonie@xxxxxxxxxx> wrote: > > We don't need to change the ABI, the ABI just says we zero the registers > > that aren't shared with FPSIMD. Instead of doing that on taking a SVE > > access trap to reenable SVE after having disabled TIF_SVE we could do > That's not the point I'm trying to make. > Userspace expects to have lost SVE information over a syscall (even if > the VL is 128, it expects to have lost P0..P15 and FFR). How do you > plan to tell userspace that this behaviour has changed? My point is that this doesn't need to change. Userspace can't tell if we zeroed the non-shared state on syscall or on some later access trap.
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