[PATCH 1/3] KVM: ARM: fix the size of TTBCR_{T0SZ,T1SZ} masks

[Christoffer Dall]

On Thu, Sep 26, 2013 at 04:49:26PM +0100, Jonathan Austin wrote:
> The T{0,1}SZ fields of TTBCR are 3 bits wide when using the long descriptor
> format. Likewise, the T0SZ field of the HTCR is 3-bits. KVM currently
> defines TTBCR_T{0,1}SZ as 3, not 7.
> 
> The T0SZ mask is used to calculate the value for the HTCR, both to pick out
> TTBCR.T0SZ and mask off the equivalent field in the HTCR during
> read-modify-write. The incorrect mask size causes the (UNKNOWN) reset value
> of HTCR.T0SZ to leak in to the calculated HTCR value. Linux will hang when
> initializing KVM if HTCR's reset value has bit 2 set (sometimes the case on
> A7/TC2)
> 
> Fixing T0SZ allows A7 cores to boot and T1SZ is also fixed for completeness.
> 
> Signed-off-by: Jonathan Austin <jonathan.austin at arm.com>
> Acked-by: Marc Zyngier <marc.zyngier at arm.com>
> ---
>  arch/arm/include/asm/kvm_arm.h |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/include/asm/kvm_arm.h b/arch/arm/include/asm/kvm_arm.h
> index 64e9696..d556f03 100644
> --- a/arch/arm/include/asm/kvm_arm.h
> +++ b/arch/arm/include/asm/kvm_arm.h
> @@ -95,12 +95,12 @@
>  #define TTBCR_IRGN1	(3 << 24)
>  #define TTBCR_EPD1	(1 << 23)
>  #define TTBCR_A1	(1 << 22)
> -#define TTBCR_T1SZ	(3 << 16)
> +#define TTBCR_T1SZ	(7 << 16)
>  #define TTBCR_SH0	(3 << 12)
>  #define TTBCR_ORGN0	(3 << 10)
>  #define TTBCR_IRGN0	(3 << 8)
>  #define TTBCR_EPD0	(1 << 7)
> -#define TTBCR_T0SZ	3
> +#define TTBCR_T0SZ	(7 << 0)
>  #define HTCR_MASK	(TTBCR_T0SZ | TTBCR_IRGN0 | TTBCR_ORGN0 | TTBCR_SH0)
>  
>  /* Hyp System Trap Register */
> -- 
> 1.7.9.5
> 
Good catch!

ack.

-Christoffer