[Qemu-devel] Re: [PATCH 4/5] kvmppc: Translate eaddr for fsl_booke mmu

[Alexander Graf]

Am 20.08.2009 um 12:21 schrieb "Liu Yu-B13201" <address@hidden>:

> > -----Original Message-----
> > From: Hollis Blanchard [mailto:address@hidden
> > Sent: Thursday, August 20, 2009 6:51 AM
> > To: Liu Yu-B13201
> > Cc: address@hidden; address@hidden;
> > address@hidden; address@hidden; Alexander Graf
> > Subject: Re: [PATCH 4/5] kvmppc: Translate eaddr for fsl_booke mmu
> >
> > On Tue, 2009-08-04 at 17:36 +0800, Liu Yu wrote:
> > > Signed-off-by: Liu Yu <address@hidden>
> > > ---
> > > target-ppc/helper.c |   17 +++++++++++++++--
> > > 1 files changed, 15 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/target-ppc/helper.c b/target-ppc/helper.c
> > > index 6eca2e5..07e56a4 100644
> > > --- a/target-ppc/helper.c
> > > +++ b/target-ppc/helper.c
> > > @@ -22,6 +22,7 @@
> > > #include <string.h>
> > > #include <inttypes.h>
> > > #include <signal.h>
> > > +#include <linux/kvm.h>
> > >
> > > #include "cpu.h"
> > > #include "exec-all.h"
> > > @@ -1325,8 +1326,20 @@ static always_inline int
> > check_physical (CPUState *env, mmu_ctx_t *ctx,
> > >         cpu_abort(env, "MPC8xx MMU model is not implemented\n");
> > >         break;
> > >     case POWERPC_MMU_BOOKE_FSL:
> > > -        /* XXX: TODO */
> > > -        cpu_abort(env, "BookE FSL MMU model not implemented\n");
> > > +        if (kvm_enabled()) {
> > > +            struct kvm_translation tr;
> > > +
> > > +            /* For now we only debug guest kernel */
> > > +            tr.linear_address = eaddr;
> > > +            ret = kvm_vcpu_ioctl(env, KVM_TRANSLATE, &tr);
> > > +            if (ret < 0)
> > > +                return ret;
> > > +
> > > +            ctx->raddr = tr.physical_address;
> > > +        } else {
> > > +            /* XXX: TODO */
> > > +            cpu_abort(env, "BookE FSL MMU model not
> > implemented\n");
> > > +        }
> > >         break;
> > >     default:
> > >         cpu_abort(env, "Unknown or invalid MMU model\n");
> >
> > One objection: the comment is a little obscure. I think what you're
> > really saying is "in Linux guests, kernel addresses should always be
> > covered by TLB1, which means for those addresses we can expect this
> > ioctl to succeed." However, since you need to handle failures
> > anyways, I
> > think you should remove the comment entirely.
>
> As BOOKE mmu translation needs AS + PID + address,
> The infomations we pass to kvmppc here only count in address and set
> AS=0, PID=0.
> Which indicates that it's a kernel address.
>
> If want to translate user space address, one way is read registers  
> from
> kvmppc at first
> and then pass the correct AS and PID to translator.
> As we don't need to debug guest userspace, for simplicity, I didn't do
> that.
>
> > Second, (and this isn't an objection but rather a question)
> > do you have
> > any better ideas for struct kvm_translation? It only really
> > makes sense
> > for x86. We don't need to stick with it.
>
> Hrr.. We need to combine AS, PID and 32-bit addr into 64-bit linear
> address. it's not that convenient.
> But except that, I am not sure if there is strong requirement to  
> change
> it...
>
> BOOK3S KVM has more work in qemu (openbios, vga etc.),
> Maybe Alex has some suggestion?

What does that do again? Enable userspace to do EA to PA translation?

IMHO userspace should do the translation and do an ioctl to fetch the  
required information (soft TLB cache / SLB / SDR1) so we can reuse the  
existing qemu infrastructure.

Alex