On Tue, Oct 31, 2017 at 03:51:07PM +0000, Dave P Martin wrote: > This patch implements support for saving and restoring the SVE > registers around signals. > > A fixed-size header struct sve_context is always included in the > signal frame encoding the thread's vector length at the time of > signal delivery, optionally followed by a variable-layout structure > encoding the SVE registers. > > Because of the need to preserve backwards compatibility, the FPSIMD > view of the SVE registers is always dumped as a struct > fpsimd_context in the usual way, in addition to any sve_context. > > The SVE vector registers are dumped in full, including bits 127:0 > of each register which alias the corresponding FPSIMD vector > registers in the hardware. To avoid any ambiguity about which > alias to restore during sigreturn, the kernel always restores bits > 127:0 of each SVE vector register from the fpsimd_context in the > signal frame (which must be present): userspace needs to take this > into account if it wants to modify the SVE vector register contents > on return from a signal. > > FPSR and FPCR, which are used by both FPSIMD and SVE, are not > included in sve_context because they are always present in > fpsimd_context anyway. > > For signal delivery, a new helper > fpsimd_signal_preserve_current_state() is added to update _both_ > the FPSIMD and SVE views in the task struct, to make it easier to > populate this information into the signal frame. Because of the > redundancy between the two views of the state, only one is updated > otherwise. > > Signed-off-by: Dave Martin <Dave.Martin@xxxxxxx> > Cc: Alex Bennée <alex.bennee@xxxxxxxxxx> > Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> > Cc: Will Deacon <will.deacon@xxxxxxx> Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
