Re: [PATCH v2 02/10] KVM: define common __KVM_GUESTDBG_USE_SW/HW_BP values

Christoffer Dall
2015-04-13T11:47:45Z

On Tue, Mar 31, 2015 at 04:08:00PM +0100, Alex Bennée wrote:
> Currently x86, powerpc and soon arm64 use the same two architecture
> specific bits for guest debug support for software and hardware
> breakpoints. This makes the shared values explicit while leaving the
> gate open for another architecture to use some other value if they
> really really want to.
>
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>
> diff --git a/arch/powerpc/include/uapi/asm/kvm.h b/arch/powerpc/include/uapi/asm/kvm.h
> index ab4d473..1731569 100644
> --- a/arch/powerpc/include/uapi/asm/kvm.h
> +++ b/arch/powerpc/include/uapi/asm/kvm.h
> @@ -310,8 +310,8 @@ struct kvm_guest_debug_arch {
> * and upper 16 bits are architecture specific. Architecture specific defines
> * that ioctl is for setting hardware breakpoint or software breakpoint.
> */
> -#define KVM_GUESTDBG_USE_SW_BP 0x00010000
> -#define KVM_GUESTDBG_USE_HW_BP 0x00020000
> +#define KVM_GUESTDBG_USE_SW_BP __KVM_GUESTDBG_USE_SW_BP
> +#define KVM_GUESTDBG_USE_HW_BP __KVM_GUESTDBG_USE_HW_BP
>
> /* definition of registers in kvm_run */
> struct kvm_sync_regs {
> diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
> index d7dcef5..1438202 100644
> --- a/arch/x86/include/uapi/asm/kvm.h
> +++ b/arch/x86/include/uapi/asm/kvm.h
> @@ -250,8 +250,8 @@ struct kvm_debug_exit_arch {
> __u64 dr7;
> };
>
> -#define KVM_GUESTDBG_USE_SW_BP 0x00010000
> -#define KVM_GUESTDBG_USE_HW_BP 0x00020000
> +#define KVM_GUESTDBG_USE_SW_BP __KVM_GUESTDBG_USE_SW_BP
> +#define KVM_GUESTDBG_USE_HW_BP __KVM_GUESTDBG_USE_HW_BP
> #define KVM_GUESTDBG_INJECT_DB 0x00040000
> #define KVM_GUESTDBG_INJECT_BP 0x00080000
>
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 5eedf84..ce2db14 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -525,8 +525,16 @@ struct kvm_s390_irq {
>
> /* for KVM_SET_GUEST_DEBUG */
>
> -#define KVM_GUESTDBG_ENABLE 0x00000001
> -#define KVM_GUESTDBG_SINGLESTEP 0x00000002
> +#define KVM_GUESTDBG_ENABLE (1 << 0)
> +#define KVM_GUESTDBG_SINGLESTEP (1 << 1)
> +
> +/*
> + * Architecture specific stuff uses the top 16 bits of the field,

can you be more specific than 'stuff' here? features?

> + * however there is some shared commonality for the common cases

I don't like this sentence; shared commonality is a pleonasm and the use
of however makes it sounds like there's some caveat here.

If the top 16 bits are indeed arhictecture specific, then I think they
should just be defined in their architecture specific headers. Unless
the idea here is that there's a fixed set of of flags that architectures
can choose to support, in which case it should simply be defined in the
common header.

> + */
> +#define __KVM_GUESTDBG_USE_SW_BP (1 << 16)
> +#define __KVM_GUESTDBG_USE_HW_BP (1 << 17)
> +
>
> struct kvm_guest_debug {
> __u32 control;
> --
> 2.3.4
>