On Tue, Nov 07, 2017 at 01:22:33PM +0000, Alex Bennée wrote: > > Dave Martin <Dave.Martin@xxxxxxx> writes: > > > 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> > > After adding SVE support for RISU I was able to confirm consistent > signal delivery with a decent context over multiple runs and after > hacking echo "32" > /proc/sys/abi/sve_default_vector_length to change > the default length the tests would fail (as expected). > > Tested-by: Alex Bennée <alex.bennee@xxxxxxxxxx> Good to have confirmation of this, thanks [...] Cheers ---Dave
