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arm64: KVM: Obey RES0/1 reserved bits when setting CPTR_EL2

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Some bits in CPTR are defined as RES1 in the architecture.  Setting
these bits to zero may unintentionally enable future architecture
extensions, allowing guests to use them without supervision by the host.

This would be bad: for forwards compatibility, this patch makes
sure the affected bits are always written with 1, not 0.

This patch only addresses CPTR_EL2.  Initialisation of other system
registers may still need review.

Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
This commit is contained in:
Dave Martin
2016-01-19 16:20:18 +00:00
committed by Marc Zyngier
parent 8fc153cda9
commit a7e0ac295d
2 changed files with 7 additions and 2 deletions
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8
arch/arm64/kvm/hyp/switch.c
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@@ -36,7 +36,11 @@ static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
write_sysreg(val, hcr_el2);
/* Trap on AArch32 cp15 c15 accesses (EL1 or EL0) */
write_sysreg(1 << 15, hstr_el2);
write_sysreg(CPTR_EL2_TTA | CPTR_EL2_TFP, cptr_el2);
val = CPTR_EL2_DEFAULT;
val |= CPTR_EL2_TTA | CPTR_EL2_TFP;
write_sysreg(val, cptr_el2);
write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
}
@@ -45,7 +49,7 @@ static void __hyp_text __deactivate_traps(struct kvm_vcpu *vcpu)
write_sysreg(HCR_RW, hcr_el2);
write_sysreg(0, hstr_el2);
write_sysreg(read_sysreg(mdcr_el2) & MDCR_EL2_HPMN_MASK, mdcr_el2);
write_sysreg(0, cptr_el2);
write_sysreg(CPTR_EL2_DEFAULT, cptr_el2);
}
static void __hyp_text __activate_vm(struct kvm_vcpu *vcpu)