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armv8: Handle EL2 Host mode

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On implementations that support VHE, the layout of the CPTR_EL2
register depends on whether HCR_EL2.E2H is set.  If the bit is
set, CPTR_EL2 uses the same layout as CPACR_EL1 and can in fact
be accessed through that register.  In that case, jump to the
EL1 code to enable access to the FP/SIMD registers.  This allows
U-Boot to run on systems that pass control to U-Boot in EL2 with
EL2 Host mode enabled such as machines using Apple's M1 SoC.

Signed-off-by: Mark Kettenis <kettenis@openbsd.org>
Acked-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Mark Kettenis 2021-02-10 20:14:55 +01:00 committed by Tom Rini
parent fd075f77ca
commit bfb798461a
1 changed files with 4 additions and 2 deletions
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6
arch/arm/cpu/armv8/start.S
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@ -132,11 +132,13 @@ pie_fixup_done:
msr cntfrq_el0, x0 /* Initialize CNTFRQ */
#endif
b 0f
2: set_vbar vbar_el2, x0
2: mrs x1, hcr_el2
tbnz x1, #34, 1f /* HCR_EL2.E2H */
set_vbar vbar_el2, x0
mov x0, #0x33ff
msr cptr_el2, x0 /* Enable FP/SIMD */
b 0f
1: set_vbar vbar_el1, x0
1: set_vbar vbar_el1, x0
mov x0, #3 << 20
msr cpacr_el1, x0 /* Enable FP/SIMD */
0: