Dave Martin <Dave.Martin@xxxxxxx> writes: > To enable the kernel to use SVE, SVE traps from EL1 to EL2 must be > disabled. To take maximum advantage of the hardware, the full > available vector length also needs to be enabled for EL1 by > programming ZCR_EL2.LEN. (The kernel will program ZCR_EL1.LEN as > required, but this cannot override the limit set by ZCR_EL2.) > > This patch makes the appropriate changes to the EL2 early setup > code. > > Signed-off-by: Dave Martin <Dave.Martin@xxxxxxx> > Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx> > Cc: Alex Bennée <alex.bennee@xxxxxxxxxx> > > --- > > **Dropped at v3** Reviewed-by: Alex Bennée <alex.bennee@xxxxxxxxxx> > (Due to significant changes to the logic.) Have it back: Reviewed-by: Alex Bennée <alex.bennee@xxxxxxxxxx> > --- > arch/arm64/kernel/head.S | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > index cfa90a4..67e86a0 100644 > --- a/arch/arm64/kernel/head.S > +++ b/arch/arm64/kernel/head.S > @@ -524,8 +524,19 @@ CPU_LE( movk x0, #0x30d0, lsl #16 ) // Clear EE and E0E on LE systems > mov x0, #0x33ff > msr cptr_el2, x0 // Disable copro. traps to EL2 > > + /* SVE register access */ > + mrs x1, id_aa64pfr0_el1 > + ubfx x1, x1, #ID_AA64PFR0_SVE_SHIFT, #4 > + cbz x1, 7f > + > + bic x0, x0, #CPTR_EL2_TZ // Also disable SVE traps > + msr cptr_el2, x0 // Disable copro. traps to EL2 > + isb > + mov x1, #ZCR_ELx_LEN_MASK // SVE: Enable full vector > + msr_s SYS_ZCR_EL2, x1 // length for EL1. > + > /* Hypervisor stub */ > - adr_l x0, __hyp_stub_vectors > +7: adr_l x0, __hyp_stub_vectors > msr vbar_el2, x0 > > /* spsr */ -- Alex Bennée
