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arm64: Support systems without FP/ASIMD

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The arm64 kernel assumes that FP/ASIMD units are always present
and accesses the FP/ASIMD specific registers unconditionally. This
could cause problems when they are absent. This patch adds the
support for kernel handling systems without FP/ASIMD by skipping the
register access within the kernel. For kvm, we trap the accesses
to FP/ASIMD and inject an undefined instruction exception to the VM.

The callers of the exported kernel_neon_begin_partial() should
make sure that the FP/ASIMD is supported.

Cc: Will Deacon <will.deacon@arm.com>
Cc: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
[catalin.marinas@arm.com: add comment on the ARM64_HAS_NO_FPSIMD conflict and the new location]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Suzuki K Poulose
2016-11-08 13:56:21 +00:00
committed by Catalin Marinas
parent a4023f6827
commit 82e0191a1a
7 changed files with 65 additions and 4 deletions
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9
arch/arm64/kvm/hyp/hyp-entry.S
View File

@@ -106,9 +106,16 @@ el1_trap:
* x0: ESR_EC
*/
/* Guest accessed VFP/SIMD registers, save host, restore Guest */
/*
* We trap the first access to the FP/SIMD to save the host context
* and restore the guest context lazily.
* If FP/SIMD is not implemented, handle the trap and inject an
* undefined instruction exception to the guest.
*/
alternative_if_not ARM64_HAS_NO_FPSIMD
cmp x0, #ESR_ELx_EC_FP_ASIMD
b.eq __fpsimd_guest_restore
alternative_else_nop_endif
mrs x1, tpidr_el2
mov x0, #ARM_EXCEPTION_TRAP

5
arch/arm64/kvm/hyp/switch.c
View File

@@ -21,6 +21,7 @@
#include <asm/kvm_asm.h>
#include <asm/kvm_emulate.h>
#include <asm/kvm_hyp.h>
#include <asm/fpsimd.h>
static bool __hyp_text __fpsimd_enabled_nvhe(void)
{
@@ -76,9 +77,11 @@ static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
* traps are only taken to EL2 if the operation would not otherwise
* trap to EL1. Therefore, always make sure that for 32-bit guests,
* we set FPEXC.EN to prevent traps to EL1, when setting the TFP bit.
* If FP/ASIMD is not implemented, FPEXC is UNDEFINED and any access to
* it will cause an exception.
*/
val = vcpu->arch.hcr_el2;
if (!(val & HCR_RW)) {
if (!(val & HCR_RW) && system_supports_fpsimd()) {
write_sysreg(1 << 30, fpexc32_el2);
isb();
}