Re: [PATCH 6/6] KVM: booke/bookehv: Add debug stub support

[Scott Wood <scottwood@freescale.com>]

On 08/21/2012 08:52 AM, Bharat Bhushan wrote:
> This patch adds the debug stub support on booke/bookehv.
> Now QEMU debug stub can use hw breakpoint, watchpoint and
> software breakpoint to debug guest.
> 
> Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
> ---
>  arch/powerpc/include/asm/kvm.h        |   29 ++++++-
>  arch/powerpc/include/asm/kvm_host.h   |    5 +
>  arch/powerpc/kernel/asm-offsets.c     |   26 ++++++
>  arch/powerpc/kvm/booke.c              |  144 +++++++++++++++++++++++++++++----
>  arch/powerpc/kvm/booke_interrupts.S   |  110 +++++++++++++++++++++++++
>  arch/powerpc/kvm/bookehv_interrupts.S |  141 +++++++++++++++++++++++++++++++-
>  arch/powerpc/kvm/e500mc.c             |    3 +-
>  7 files changed, 435 insertions(+), 23 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/kvm.h b/arch/powerpc/include/asm/kvm.h
> index 61b197e..53479ea 100644
> --- a/arch/powerpc/include/asm/kvm.h
> +++ b/arch/powerpc/include/asm/kvm.h
> @@ -25,6 +25,7 @@
>  /* Select powerpc specific features in <linux/kvm.h> */
>  #define __KVM_HAVE_SPAPR_TCE
>  #define __KVM_HAVE_PPC_SMT
> +#define __KVM_HAVE_GUEST_DEBUG
>  
>  struct kvm_regs {
>  	__u64 pc;
> @@ -264,7 +265,31 @@ struct kvm_fpu {
>  	__u64 fpr[32];
>  };
>  
> +
> +/*
> + * Defines for h/w breakpoint, watchpoint (read, write or both) and
> + * software breakpoint.
> + * These are used as "type" in KVM_SET_GUEST_DEBUG ioctl and "status"
> + * for KVM_DEBUG_EXIT.
> + */
> +#define KVMPPC_DEBUG_NONE		0x0
> +#define KVMPPC_DEBUG_BREAKPOINT		(1UL << 1)
> +#define KVMPPC_DEBUG_WATCH_WRITE	(1UL << 2)
> +#define KVMPPC_DEBUG_WATCH_READ		(1UL << 3)
>  struct kvm_debug_exit_arch {

That says "arch", but it's not in an arch-specific file.

> +	__u64 pc;
> +	/*
> +	 * exception -> returns the exception number. If the KVM_DEBUG_EXIT
> +	 * exit is not handled (say not h/w breakpoint or software breakpoint
> +	 * set for this address) by qemu then it is supposed to inject this
> +	 * exception to guest.
> +	 */
> +	__u32 exception;
> +	/*
> +	 * exiting to userspace because of h/w breakpoint, watchpoint
> +	 * (read, write or both) and software breakpoint.
> +	 */
> +	__u32 status;
>  };

What does "exception number" mean in a generic API?

What values can go in "status"?

> +	addi	r7, r4, VCPU_HOST_DBG
> +	mfspr	r9, SPRN_DBCR0
> +	lwz	r8, KVMPPC_DBG_DBCR0(r7)
> +	andis.	r9, r9, DBCR0_AC_BITS@h
> +	beq	skip_load_host_debug
> +	li	r9, 0
> +	mtspr	SPRN_DBCR0, r9		/* disable all debug event */
> +	lwz	r9, KVMPPC_DBG_DBCR1(r7)
> +	mtspr	SPRN_DBCR1, r9
> +	lwz	r9, KVMPPC_DBG_DBCR2(r7)
> +	mtspr	SPRN_DBCR2, r9
> +	lwz	r9, KVMPPC_DBG_IAC1+4(r7)
> +	mtspr	SPRN_IAC1, r9
> +	lwz	r9, KVMPPC_DBG_IAC2+4(r7)
> +	mtspr	SPRN_IAC2, r9
> +#if CONFIG_PPC_ADV_DEBUG_IACS > 2
> +	lwz	r9, KVMPPC_DBG_IAC3+4(r7)
> +	mtspr	SPRN_IAC3, r9
> +	lwz	r9, KVMPPC_DBG_IAC4+4(r7)
> +	mtspr	SPRN_IAC4, r9
> +#endif

What if CONFIG_PPC_ADV_DEBUG_REGS isn't set?

-Scott