Dave Martin <Dave.Martin@xxxxxxx> writes: > To enable the kernel to use SVE, all SVE traps from EL1 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.) > > In advance of full SVE support being implemented for userspace, it > also necessary to ensure that SVE traps from EL0 are enabled. > > This patch makes the appropriate changes to the primary and > secondary CPU initialisation code. > > Signed-off-by: Dave Martin <Dave.Martin@xxxxxxx> > --- > arch/arm64/kernel/head.S | 13 ++++++++++++- > arch/arm64/mm/proc.S | 14 ++++++++++++-- > 2 files changed, 24 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > index 973df7d..0ae1713 100644 > --- a/arch/arm64/kernel/head.S > +++ b/arch/arm64/kernel/head.S > @@ -514,8 +514,19 @@ 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 It seems a shame to write to cptr_el2 twice rather than compute and write. > + isb Especially as the second one needs an isb :-/ But I don't see a much neater way of doing it so: Reviewed-by: Alex Bennée <alex.bennee@xxxxxxxxxx> > + 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 */ > diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S > index 877d42f..dd22ef2 100644 > --- a/arch/arm64/mm/proc.S > +++ b/arch/arm64/mm/proc.S > @@ -27,6 +27,7 @@ > #include <asm/pgtable-hwdef.h> > #include <asm/cpufeature.h> > #include <asm/alternative.h> > +#include <asm/sysreg.h> > > #ifdef CONFIG_ARM64_64K_PAGES > #define TCR_TG_FLAGS TCR_TG0_64K | TCR_TG1_64K > @@ -186,8 +187,17 @@ ENTRY(__cpu_setup) > tlbi vmalle1 // Invalidate local TLB > dsb nsh > > - mov x0, #3 << 20 > - msr cpacr_el1, x0 // Enable FP/ASIMD > + mov x0, #3 << 20 // FEN > + > + /* SVE */ > + mrs x5, id_aa64pfr0_el1 > + ubfx x5, x5, #ID_AA64PFR0_SVE_SHIFT, #4 > + cbz x5, 1f > + > + bic x0, x0, #CPACR_EL1_ZEN > + orr x0, x0, #CPACR_EL1_ZEN_EL1EN // SVE: trap for EL0, not EL1 > +1: msr cpacr_el1, x0 // Enable FP/ASIMD > + > mov x0, #1 << 12 // Reset mdscr_el1 and disable > msr mdscr_el1, x0 // access to the DCC from EL0 > isb // Unmask debug exceptions now, -- Alex Bennée
