Re: [RFC PATCH v2 16/22] i386/xen: handle VCPUOP_register_vcpu_info

[David Woodhouse]

On Mon, 2022-12-12 at 14:58 +0000, Paul Durrant wrote:
> On 09/12/2022 09:56, David Woodhouse wrote:
> > From: Joao Martins <
> > joao.m.martins@oracle.com
> > >
> > 
> > Handle the hypercall to set a per vcpu info, and also wire up the
> > default
> > vcpu_info in the shared_info page for the first 32 vCPUs.
> > 
> > To avoid deadlock within KVM a vCPU thread must set its *own*
> > vcpu_info
> > rather than it being set from the context in which the hypercall is
> > invoked.
> > 
> > Add the vcpu_info (and default) GPA to the vmstate_x86_cpu for
> > migration,
> > and restore it in kvm_arch_put_registers() appropriately.
> > 
> > Signed-off-by: Joao Martins <
> > joao.m.martins@oracle.com
> > >
> > Signed-off-by: David Woodhouse <
> > dwmw@amazon.co.uk
> > >
> > ---
> >   target/i386/cpu.h        |  2 ++
> >   target/i386/kvm/kvm.c    | 19 +++++++++++
> >   target/i386/machine.c    | 21 ++++++++++++
> >   target/i386/trace-events |  1 +
> >   target/i386/xen.c        | 74
> > +++++++++++++++++++++++++++++++++++++---
> >   target/i386/xen.h        |  1 +
> >   6 files changed, 113 insertions(+), 5 deletions(-)
> > 
> > diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> > index c6c57baed5..109b2e5669 100644
> > --- a/target/i386/cpu.h
> > +++ b/target/i386/cpu.h
> > @@ -1788,6 +1788,8 @@ typedef struct CPUArchState {
> >   #endif
> >   #if defined(CONFIG_KVM)
> >       struct kvm_nested_state *nested_state;
> > +    uint64_t xen_vcpu_info_gpa;
> > +    uint64_t xen_vcpu_info_default_gpa;
> >   #endif
> >   #if defined(CONFIG_HVF)
> >       HVFX86LazyFlags hvf_lflags;
> > diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
> > index ebde6bc204..fa45e2f99a 100644
> > --- a/target/i386/kvm/kvm.c
> > +++ b/target/i386/kvm/kvm.c
> > @@ -1811,6 +1811,9 @@ int kvm_arch_init_vcpu(CPUState *cs)
> >           has_msr_hv_hypercall = true;
> >       }
> >   
> > +    env->xen_vcpu_info_gpa = UINT64_MAX;
> > +    env->xen_vcpu_info_default_gpa = UINT64_MAX;
> 
> 
> There was an INVALID_GPA definition for shared info. Looks like we
> could use it here too.

There was, and I started trying to use it, but it fell foul of the "is
this going to live in target/ or hw/ and who can include what from
where?" and I decided to just use UINT64_MAX for now and keep typing.

That will work out in the end, I'm sure.

> Some sanity checks wouldn't go a miss here...
> 
> rvi.offset should:
> a) be < TARGET_PAGE_SIZE, and
> b) ba aligned to vcpu_info_t size

Ack.

smime.p7s
Description: S/MIME cryptographic signature