Re: [PATCH v2 7/9] arm64: KVM: add trap handlers for AArch32 debug registers

Christoffer Dall
2014-05-25T15:35:51Z

On Tue, May 20, 2014 at 05:55:43PM +0100, Marc Zyngier wrote:
> Add handlers for all the AArch32 debug registers that are accessible
> from EL0 or EL1. The code follow the same strategy as the AArch64
> counterpart with regards to tracking the dirty state of the debug
> registers.
>
> Reviewed-by: Anup Patel <anup.patel@linaro.org>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
> arch/arm64/include/asm/kvm_asm.h | 9 +++
> arch/arm64/kvm/sys_regs.c | 137 ++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 145 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
> index 12f9dd7..993a7db 100644
> --- a/arch/arm64/include/asm/kvm_asm.h
> +++ b/arch/arm64/include/asm/kvm_asm.h
> @@ -93,6 +93,15 @@
> #define c10_AMAIR0 (AMAIR_EL1 * 2) /* Aux Memory Attr Indirection Reg */
> #define c10_AMAIR1 (c10_AMAIR0 + 1)/* Aux Memory Attr Indirection Reg */
> #define c14_CNTKCTL (CNTKCTL_EL1 * 2) /* Timer Control Register (PL1) */
> +
> +#define cp14_DBGDSCRext (MDSCR_EL1 * 2)
> +#define cp14_DBGBCR0 (DBGBCR0_EL1 * 2)
> +#define cp14_DBGBVR0 (DBGBVR0_EL1 * 2)
> +#define cp14_DBGBXVR0 (cp14_DBGBVR0 + 1)
> +#define cp14_DBGWCR0 (DBGWCR0_EL1 * 2)
> +#define cp14_DBGWVR0 (DBGWVR0_EL1 * 2)
> +#define cp14_DBGDCCINT (MDCCINT_EL1 * 2)
> +
> #define NR_COPRO_REGS (NR_SYS_REGS * 2)
>
> #define ARM_EXCEPTION_IRQ 0
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 98d60d1..5960d5b 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -474,12 +474,148 @@ static const struct sys_reg_desc sys_reg_descs[] = {
> NULL, reset_val, FPEXC32_EL2, 0x70 },
> };
>
> +static bool trap_dbgidr(struct kvm_vcpu *vcpu,
> + const struct sys_reg_params *p,
> + const struct sys_reg_desc *r)
> +{
> + if (p->is_write) {
> + return ignore_write(vcpu, p);
> + } else {
> + u64 dfr = read_cpuid(ID_AA64DFR0_EL1);
> + u64 pfr = read_cpuid(ID_AA64PFR0_EL1);
> + u32 el3 = !!((pfr >> 12) & 0xf);
> +
> + *vcpu_reg(vcpu, p->Rt) = ((((dfr >> 20) & 0xf) << 28) |
> + (((dfr >> 12) & 0xf) << 24) |
> + (((dfr >> 28) & 0xf) << 20) |
> + (6 << 16) | (el3 << 14) | (el3 << 12));
> + return true;
> + }
> +}
> +
> +static bool trap_debug32(struct kvm_vcpu *vcpu,
> + const struct sys_reg_params *p,
> + const struct sys_reg_desc *r)
> +{
> + if (p->is_write) {
> + vcpu_cp14(vcpu, r->reg) = *vcpu_reg(vcpu, p->Rt);
> + vcpu->arch.debug_flags |= KVM_ARM64_DEBUG_DIRTY;
> + } else {
> + *vcpu_reg(vcpu, p->Rt) = vcpu_cp14(vcpu, r->reg);
> + }
> +
> + return true;
> +}
> +
> +#define DBG_BCR_BVR_WCR_WVR(n) \
> + /* DBGBCRn */ \
> + { Op1( 0), CRn( 0), CRm((n)), Op2( 4), trap_debug32, \
> + NULL, (cp14_DBGBCR0 + (n) * 2) }, \
> + /* DBGBVRn */ \
> + { Op1( 0), CRn( 0), CRm((n)), Op2( 5), trap_debug32, \
> + NULL, (cp14_DBGBVR0 + (n) * 2) }, \

I think you switched the order of DBGBCRn and DBGBVRn here? Opc2==4 is
the DBGBVR and Opc2==5 is the DBGBCR0.

> + /* DBGWVRn */ \
> + { Op1( 0), CRn( 0), CRm((n)), Op2( 6), trap_debug32, \
> + NULL, (cp14_DBGWVR0 + (n) * 2) }, \
> + /* DBGWCRn */ \
> + { Op1( 0), CRn( 0), CRm((n)), Op2( 7), trap_debug32, \
> + NULL, (cp14_DBGWCR0 + (n) * 2) }
> +
> +#define DBGBXVR(n) \
> + { Op1( 0), CRn( 1), CRm((n)), Op2( 1), trap_debug32, \
> + NULL, cp14_DBGBXVR0 + n * 2 }
> +
> /* Trapped cp14 registers */
> static const struct sys_reg_desc cp14_regs[] = {
> + /* DBGIDR */
> + { Op1( 0), CRn( 0), CRm( 0), Op2( 0), trap_dbgidr },
> + /* DBGDTRRXext */
> + { Op1( 0), CRn( 0), CRm( 0), Op2( 2), trap_raz_wi },
> +
> + DBG_BCR_BVR_WCR_WVR(0),
> + /* DBGDSCRint */
> + { Op1( 0), CRn( 0), CRm( 1), Op2( 0), trap_raz_wi },
> + DBG_BCR_BVR_WCR_WVR(1),
> + /* DBGDCCINT */
> + { Op1( 0), CRn( 0), CRm( 2), Op2( 0), trap_debug32 },
> + /* DBGDSCRext */
> + { Op1( 0), CRn( 0), CRm( 2), Op2( 2), trap_debug32 },
> + DBG_BCR_BVR_WCR_WVR(2),
> + /* DBGDTRTXext */
> + { Op1( 0), CRn( 0), CRm( 3), Op2( 2), trap_raz_wi },
> + DBG_BCR_BVR_WCR_WVR(3),
> + DBG_BCR_BVR_WCR_WVR(4),

So we don't have a handler for the TRRX_int (nor the TRRX_EL0). I
understand that it doesn't make sense to keep state for them or
context-switch them, but do we never trap on these and if we do, is it
then always valid to inject an undefined exception?

> + DBG_BCR_BVR_WCR_WVR(5),
> + /* DBGWFAR */
> + { Op1( 0), CRn( 0), CRm( 6), Op2( 0), trap_raz_wi },
> + /* DBGOSECCR */
> + { Op1( 0), CRn( 0), CRm( 6), Op2( 2), trap_raz_wi },

So it seems that we generally ignore everything related to external
debug state, but we don't really document anywhere what our behavior is
and what is and what is not supported towards the guest...

> + DBG_BCR_BVR_WCR_WVR(6),
> + /* DBGVCR */
> + { Op1( 0), CRn( 0), CRm( 7), Op2( 0), trap_debug32 },
> + DBG_BCR_BVR_WCR_WVR(7),
> + DBG_BCR_BVR_WCR_WVR(8),
> + DBG_BCR_BVR_WCR_WVR(9),
> + DBG_BCR_BVR_WCR_WVR(10),
> + DBG_BCR_BVR_WCR_WVR(11),
> + DBG_BCR_BVR_WCR_WVR(12),
> + DBG_BCR_BVR_WCR_WVR(13),
> + DBG_BCR_BVR_WCR_WVR(14),
> + DBG_BCR_BVR_WCR_WVR(15),
> +
> + /* DBGDRAR (32bit) */
> + { Op1( 0), CRn( 1), CRm( 0), Op2( 0), trap_raz_wi },
> +
> + DBGBXVR(0),
> + /* DBGOSLAR */
> + { Op1( 0), CRn( 1), CRm( 0), Op2( 4), trap_raz_wi },
> + DBGBXVR(1),
> + /* DBGOSLSR */
> + { Op1( 0), CRn( 1), CRm( 1), Op2( 4), trap_oslsr_el1 },
> + DBGBXVR(2),
> + DBGBXVR(3),
> + /* DBGOSDLR */
> + { Op1( 0), CRn( 1), CRm( 3), Op2( 4), trap_raz_wi },
> + DBGBXVR(4),
> + /* DBGPRCR */
> + { Op1( 0), CRn( 1), CRm( 4), Op2( 4), trap_raz_wi },
> + DBGBXVR(5),
> + DBGBXVR(6),
> + DBGBXVR(7),
> + DBGBXVR(8),
> + DBGBXVR(9),
> + DBGBXVR(10),
> + DBGBXVR(11),
> + DBGBXVR(12),
> + DBGBXVR(13),
> + DBGBXVR(14),
> + DBGBXVR(15),
> +
> + /* DBGDSAR (32bit) */
> + { Op1( 0), CRn( 2), CRm( 0), Op2( 0), trap_raz_wi },
> +

we don't handle access to any implementation defined debug registers?
Did we actually check what would be implemented for the cores we
support?

> + /* DBGDEVID2 */
> + { Op1( 0), CRn( 7), CRm( 0), Op2( 7), trap_raz_wi },
> + /* DBGDEVID1 */
> + { Op1( 0), CRn( 7), CRm( 1), Op2( 7), trap_raz_wi },
> + /* DBGDEVID */
> + { Op1( 0), CRn( 7), CRm( 2), Op2( 7), trap_raz_wi },
> + /* DBGCLAIMSET */
> + { Op1( 0), CRn( 7), CRm( 8), Op2( 6), trap_raz_wi },
> + /* DBGCLAIMCLR */
> + { Op1( 0), CRn( 7), CRm( 9), Op2( 6), trap_raz_wi },
> +

nit: why the sudden blank line?

> + /* DBGAUTHSTATUS */
> + { Op1( 0), CRn( 7), CRm(14), Op2( 6), trap_dbgauthstatus_el1 },
> };
>
> /* Trapped cp14 64bit registers */
> static const struct sys_reg_desc cp14_64_regs[] = {
> + /* DBGDRAR (64bit) */
> + { Op1( 0), CRm( 1), .access = trap_raz_wi },
> +
> + /* DBGDSAR (64bit) */
> + { Op1( 0), CRm( 2), .access = trap_raz_wi },
> };
>
> /*
> @@ -527,7 +663,6 @@ static const struct sys_reg_desc cp15_regs[] = {
> { Op1( 0), CRn(10), CRm( 3), Op2( 0), access_vm_reg, NULL, c10_AMAIR0 },
> { Op1( 0), CRn(10), CRm( 3), Op2( 1), access_vm_reg, NULL, c10_AMAIR1 },
> { Op1( 0), CRn(13), CRm( 0), Op2( 1), access_vm_reg, NULL, c13_CID },
> -
> };
>
> static const struct sys_reg_desc cp15_64_regs[] = {
> --
> 1.8.3.4
>