Re: [PATCH v15 02/11] x86: add generic resource (e.g. MSR) access hypercall

[Chao Peng <chao.p.peng@linux.intel.com>]

On Fri, Sep 05, 2014 at 11:59:11AM +0100, Andrew Cooper wrote:
> On 05/09/14 09:37, Chao Peng wrote:
> > Add a generic resource access hypercall for tool stack or other
> > components, e.g., accessing MSR, port I/O, etc.
> >
> > Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com>
> > Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
> > ---
> >  xen/arch/x86/platform_hypercall.c |   63 +++++++++++++++++++++++++++++++++++++
> >  xen/include/public/platform.h     |   15 +++++++++
> >  xen/include/xlat.lst              |    1 +
> >  3 files changed, 79 insertions(+)
> >
> > diff --git a/xen/arch/x86/platform_hypercall.c b/xen/arch/x86/platform_hypercall.c
> > index 2162811..e5ad4c9 100644
> > --- a/xen/arch/x86/platform_hypercall.c
> > +++ b/xen/arch/x86/platform_hypercall.c
> > @@ -61,6 +61,42 @@ long cpu_down_helper(void *data);
> >  long core_parking_helper(void *data);
> >  uint32_t get_cur_idle_nums(void);
> >  
> > +struct xen_resource_access {
> > +    int32_t ret;
> > +    struct xenpf_resource_op *data;
> > +};
> > +
> > +static bool_t allow_access_msr(unsigned int msr)
> > +{
> > +    return 0;
> > +}
> > +
> > +static void resource_access_one(void *info)
> > +{
> > +    struct xen_resource_access *ra = info;
> > +    int ret = 0;
> > +
> > +    switch ( ra->data->cmd )
> > +    {
> > +    case XEN_RESOURCE_OP_MSR_READ:
> > +    case XEN_RESOURCE_OP_MSR_WRITE:
> > +        if ( ra->data->idx >> 32 )
> > +            ret = -EINVAL;
> > +        else if ( !allow_access_msr(ra->data->idx) )
> > +            ret = -EACCES;
> > +        else if ( ra->data->cmd == XEN_RESOURCE_OP_MSR_READ )
> > +            ret = rdmsr_safe(ra->data->idx, ra->data->val);
> > +        else
> > +            ret = wrmsr_safe(ra->data->idx, ra->data->val);
> > +        break;
> > +    default:
> > +        ret = -EINVAL;
> > +        break;
> > +    }
> > +
> > +    ra->ret = ret;
> > +}
> > +
> >  ret_t do_platform_op(XEN_GUEST_HANDLE_PARAM(xen_platform_op_t) u_xenpf_op)
> >  {
> >      ret_t ret = 0;
> > @@ -601,6 +637,33 @@ ret_t do_platform_op(XEN_GUEST_HANDLE_PARAM(xen_platform_op_t) u_xenpf_op)
> >      }
> >      break;
> >  
> > +    case XENPF_resource_op:
> > +    {
> > +        struct xen_resource_access ra;
> > +        struct xenpf_resource_op *rsc_op = &op->u.resource_op;
> > +        unsigned int cpu = smp_processor_id();
> > +
> > +        ra.data = rsc_op;
> > +
> > +        if ( rsc_op->cpu == cpu )
> > +            resource_access_one(&ra);
> > +        else if ( cpu_online(rsc_op->cpu) )
> > +            on_selected_cpus(cpumask_of(rsc_op->cpu),
> 
> You must validate rsc_op->cpu before using it.  cpumask_of(something
> large) will happily wander off the end of an array.
cpu_online() should detect this.
> 
> > +                         resource_access_one, &ra, 1);
> > +        else
> > +        {
> > +            ret = -ENODEV;
> > +            break;
> > +        }
> > +
> > +        if ( ra.ret )
> > +        {
> > +            ret = ra.ret;
> > +            break;
> > +        }
> > +    }
> > +    break;
> > +
> >      default:
> >          ret = -ENOSYS;
> >          break;
> > diff --git a/xen/include/public/platform.h b/xen/include/public/platform.h
> > index 053b9fa..3ed50de 100644
> > --- a/xen/include/public/platform.h
> > +++ b/xen/include/public/platform.h
> > @@ -527,6 +527,20 @@ struct xenpf_core_parking {
> >  typedef struct xenpf_core_parking xenpf_core_parking_t;
> >  DEFINE_XEN_GUEST_HANDLE(xenpf_core_parking_t);
> >  
> > +#define XENPF_resource_op   61
> > +
> > +#define XEN_RESOURCE_OP_MSR_READ  0
> > +#define XEN_RESOURCE_OP_MSR_WRITE 1
> > +
> > +struct xenpf_resource_op {
> > +    uint16_t cmd;       /* XEN_RESOURCE_OP_* */
> 
> There is an alignment issue here between 32 and 64bit. Putting an an
> explicit unit16_t _resd; field should fix it.
> 
> ~Andrew
OK, thanks.
> 
> > +    uint32_t cpu;
> > +    uint64_t idx;
> > +    uint64_t val;
> > +};
> > +typedef struct xenpf_resource_op xenpf_resource_op_t;
> > +DEFINE_XEN_GUEST_HANDLE(xenpf_resource_op_t);
> > +
> >  /*
> >   * ` enum neg_errnoval
> >   * ` HYPERVISOR_platform_op(const struct xen_platform_op*);
> > @@ -553,6 +567,7 @@ struct xen_platform_op {
> >          struct xenpf_cpu_hotadd        cpu_add;
> >          struct xenpf_mem_hotadd        mem_add;
> >          struct xenpf_core_parking      core_parking;
> > +        struct xenpf_resource_op       resource_op;
> >          uint8_t                        pad[128];
> >      } u;
> >  };
> > diff --git a/xen/include/xlat.lst b/xen/include/xlat.lst
> > index 9a35dd7..06ed7b9 100644
> > --- a/xen/include/xlat.lst
> > +++ b/xen/include/xlat.lst
> > @@ -88,6 +88,7 @@
> >  ?	xenpf_enter_acpi_sleep		platform.h
> >  ?	xenpf_pcpuinfo			platform.h
> >  ?	xenpf_pcpu_version		platform.h
> > +?	xenpf_resource_op		platform.h
> >  !	sched_poll			sched.h
> >  ?	sched_remote_shutdown		sched.h
> >  ?	sched_shutdown			sched.h
> 
> 
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