Re: [PATCH v3 21/23] arm64: hw_breakpoint: Allow EL2 breakpoints if running in HYP

Catalin Marinas
2016-02-08T15:56:30Z

On Wed, Feb 03, 2016 at 06:00:14PM +0000, Marc Zyngier wrote:
> @@ -76,6 +59,36 @@ static inline void decode_ctrl_reg(u32 reg,
> #define ARM_KERNEL_STEP_ACTIVE 1
> #define ARM_KERNEL_STEP_SUSPEND 2
>
> +#define DBG_HMC_HYP (1 << 13)
> +#define DBG_SSC_HYP (3 << 14)
> +
> +static inline u32 encode_ctrl_reg(struct arch_hw_breakpoint_ctrl ctrl)
> +{
> + u32 val = (ctrl.len << 5) | (ctrl.type << 3) | ctrl.enabled;
> +
> + if (is_kernel_in_hyp_mode() && ctrl.privilege == AARCH64_BREAKPOINT_EL1)
> + val |= DBG_HMC_HYP | DBG_SSC_HYP;
> + else
> + val |= ctrl.privilege << 1;
> +
> + return val;
> +}
> +
> +static inline void decode_ctrl_reg(u32 reg,
> + struct arch_hw_breakpoint_ctrl *ctrl)
> +{
> + ctrl->enabled = reg & 0x1;
> + reg >>= 1;
> + if (is_kernel_in_hyp_mode())
> + ctrl->privilege = !!(reg & (DBG_HMC_HYP >> 1));

I don't particularly like this part as it's not clear just by looking at
the code that it, in fact, generates AARCH64_BREAKPOINT_EL1. I would
make this clearer:

if (is_kernel_in_hyp_mode() && (reg & (DBG_HMC_HYP >> 1)))
ctrl->privilege = AARCH64_BREAKPOINT_EL1;

Alternatively, you could define the PMC field value as:

#define AARCH64_BREAKPOINT_EL2 0

and change the privilege to EL1 after masking, something like:

ctrl->privilege = reg & 0x3;
if (ctrl->privilege == AARCH64_BREAKPOINT_EL2)
ctrl->privilege = AARCH64_BREAKPOINT_EL1;

BTW, do we need to check is_kernel_in_hyp_mode() when decoding? Is there
anything else that could have set this SSC/HMC/PMC fields other than
encode_ctrl_reg()?

--
Catalin