On Mon, Feb 07, 2022 at 03:20:57PM +0000, Mark Brown wrote: > While we don't currently support SME in guests we do currently support it > for the host system so we need to take care of SME's impact, including > the floating point register state, when running guests. Simiarly to SVE > we need to manage the traps in CPACR_RL1, what is new is the handling of > streaming mode and ZA. > > Normally we defer any handling of the floating point register state until > the guest first uses it however if the system is in streaming mode FPSIMD > and SVE operations may generate SME traps which we would need to distinguish > from actual attempts by the guest to use SME. Rather than do this for the > time being if we are in streaming mode when entering the guest we force > the floating point state to be saved immediately and exit streaming mode, > meaning that the guest won't generate SME traps for supported operations. > > We could handle ZA in the access trap similarly to the FPSIMD/SVE state > without the disruption caused by streaming mode but for simplicity > handle it the same way as streaming mode for now. > > This will be revisited when we support SME for guests (hopefully before SME > hardware becomes available), for now it will only incur additional cost on > systems with SME and even there only if streaming mode or ZA are enabled. > > Signed-off-by: Mark Brown <broonie@xxxxxxxxxx> Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
