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List:       kvm-ppc
Subject:    Re: [PATCH 4/6] KVM: PPC: debug stub interface parameter defined
From:       Alexander Graf <agraf () suse ! de>
Date:       2012-12-17 16:56:11
Message-ID: 8A83AAEA-8F04-4B25-927F-00AAEE4B8CF3 () suse ! de
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On 04.10.2012, at 09:14, Bhushan Bharat-R65777 wrote:

> 
> 
> > -----Original Message-----
> > From: Alexander Graf [mailto:agraf@suse.de]
> > Sent: Monday, September 24, 2012 9:09 PM
> > To: Bhushan Bharat-R65777
> > Cc: kvm-ppc@vger.kernel.org; kvm@vger.kernel.org; Bhushan Bharat-R65777
> > Subject: Re: [PATCH 4/6] KVM: PPC: debug stub interface parameter defined
> > 
> > 
> > On 21.08.2012, at 15:51, Bharat Bhushan wrote:
> > 
> > > This patch defines the interface parameter for KVM_SET_GUEST_DEBUG
> > > ioctl support. Follow up patches will use this for setting up hardware
> > > breakpoints, watchpoints and software breakpoints.
> > > 
> > > Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
> > > ---
> > > arch/powerpc/include/asm/kvm.h |   33 +++++++++++++++++++++++++++++++++
> > > arch/powerpc/kvm/book3s.c      |    6 ++++++
> > > arch/powerpc/kvm/booke.c       |    6 ++++++
> > > arch/powerpc/kvm/powerpc.c     |    6 ------
> > > 4 files changed, 45 insertions(+), 6 deletions(-)
> > > 
> > > diff --git a/arch/powerpc/include/asm/kvm.h
> > > b/arch/powerpc/include/asm/kvm.h index 3c14202..61b197e 100644
> > > --- a/arch/powerpc/include/asm/kvm.h
> > > +++ b/arch/powerpc/include/asm/kvm.h
> > > @@ -269,8 +269,41 @@ struct kvm_debug_exit_arch {
> > > 
> > > /* for KVM_SET_GUEST_DEBUG */
> > > struct kvm_guest_debug_arch {
> > > +	struct {
> > > +		/* H/W breakpoint/watchpoint address */
> > > +		__u64 addr;
> > > +		/*
> > > +		 * Type denotes h/w breakpoint, read watchpoint, write
> > > +		 * watchpoint or watchpoint (both read and write).
> > > +		 */
> > > +#define KVMPPC_DEBUG_NOTYPE		0x0
> > > +#define KVMPPC_DEBUG_BREAKPOINT		(1UL << 1)
> > > +#define KVMPPC_DEBUG_WATCH_WRITE	(1UL << 2)
> > > +#define KVMPPC_DEBUG_WATCH_READ		(1UL << 3)
> > > +		__u32 type;
> > > +		__u32 pad1;
> > 
> > Why the padding?
> 
> Not sure why, I will remove this.

Oh, I think the padding makes sense - depending on the type of interrupt this could \
for example mean "break when write to address x becomes value y".

I'm not sure the amount of padding and the structure of it is the right way to go \
though: We probably want to have a union here defining type specific payloads.

> 
> > 
> > > +		__u64 pad2;
> > > +	} bp[16];
> > 
> > Why 16?
> 
> I think for now 6 (4 iac + 2 dac) is sufficient for BOOKE. We kept 16 to have some \
> room for future and other platforms.

Ok :)


Alex

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