On Wed, Oct 17, 2012 at 10:12 AM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote:
> Anton Romanov reports the following:
>
> AS arch/arm/kvm/interrupts.o
> /tmp/ccw2DnTo.s: Assembler messages:
> /tmp/ccw2DnTo.s: Error: bad immediate value for 8-bit offset (256)
>
> which is due to the vttbr field being out of reach from an ldrd
> instruction for some random configuration.
>
> Two workaround are implemented in this patch:
> - move the fields accessed by the assembly code towards the beginning
> of the structure,
> - use an add instead of an immediate indexing to load vttbr.
>
> Reported-by: Anton Romanov <theli.ua@xxxxxxxxx>
> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> ---
> arch/arm/include/asm/kvm_host.h | 17 +++++++++++------
> arch/arm/kvm/interrupts.S | 3 ++-
> 2 files changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index 4e2cd67..149c92a 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -45,6 +45,17 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu);
> void kvm_reset_coprocs(struct kvm_vcpu *vcpu);
>
> struct kvm_arch {
> + /* VTTBR value associated with below pgd and vmid */
> + u64 vttbr;
> +
> + /* Timer */
> + struct arch_timer_kvm timer;
> +
> + /*
> + * Anything that is not used directly from assembly code goes
> + * here.
> + */
> +
> /* The VMID generation used for the virt. memory system */
> u64 vmid_gen;
> u32 vmid;
> @@ -52,14 +63,8 @@ struct kvm_arch {
> /* Stage-2 page table */
> pgd_t *pgd;
>
> - /* VTTBR value associated with above pgd and vmid */
> - u64 vttbr;
> -
> /* Interrupt controller */
> struct vgic_dist vgic;
> -
> - /* Timer */
> - struct arch_timer_kvm timer;
> };
>
> #define KVM_NR_MEM_OBJS 40
> diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S
> index 775b29d..e08a985 100644
> --- a/arch/arm/kvm/interrupts.S
> +++ b/arch/arm/kvm/interrupts.S
> @@ -126,7 +126,8 @@ ENTRY(__kvm_vcpu_run)
>
> @ Set up guest memory translation
> ldr r1, [r0, #VCPU_KVM]
> - ldrd r2, r3, [r1, #KVM_VTTBR]
> + add r1, r1, #KVM_VTTBR
> + ldrd r2, r3, [r1]
> mcrr p15, 6, r2, r3, c2 @ Write VTTBR
>
> @ At this point, r0 must contain the pointer to the VCPU
> --
> 1.7.12
>
looks good, thanks.
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