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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v16 01/10] x86: add generic resource (e.g. MSR) access hypercall
On Thu, Sep 25, 2014 at 04:12:18PM -0400, Konrad Rzeszutek Wilk wrote:
> On Thu, Sep 25, 2014 at 08:57:38PM +0100, Andrew Cooper wrote:
> > On 25/09/14 11:19, Chao Peng wrote:
> > > Add a generic resource access hypercall for tool stack or other
> > > components, e.g., accessing MSR, port I/O, etc.
> > >
>
> You should include a bit more information in the description.
> Please give a bit information on what kind of parameters the
> hypercall is to have.
ok
>
> > > Signed-off-by: Dongxiao Xu <dongxiao.xu@xxxxxxxxx>
> > > Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
> > > ---
> > > xen/arch/x86/platform_hypercall.c | 90
> > > ++++++++++++++++++++++++++++++
> > > xen/arch/x86/x86_64/platform_hypercall.c | 4 ++
> > > xen/include/public/platform.h | 23 ++++++++
> > > xen/include/xlat.lst | 2 +
> > > 4 files changed, 119 insertions(+)
> > >
> > > diff --git a/xen/arch/x86/platform_hypercall.c
> > > b/xen/arch/x86/platform_hypercall.c
> > > index 2162811..081d9f5 100644
> > > --- a/xen/arch/x86/platform_hypercall.c
> > > +++ b/xen/arch/x86/platform_hypercall.c
> > > @@ -61,6 +61,68 @@ 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;
> > > + uint32_t nr;
> > > + XEN_GUEST_HANDLE(xenpf_resource_data_t) data;
> > > +};
> > > +
> > > +static bool_t allow_access_msr(unsigned int msr)
> > > +{
> > > + return 0;
> > > +}
> > > +
> > > +static void resource_access(void *info)
> > > +{
> > > + struct xen_resource_access *ra = info;
> > > + xenpf_resource_data_t data;
> > > + int ret = 0;
> > > + unsigned int i;
> > > +
> > > + for ( i = 0; i < ra->nr; i++ )
> > > + {
> > > + if ( copy_from_guest_offset(&data, ra->data, i, 1) )
> >
> > You cannot use copy_{to,from}_guest() here. You are almost certainly on
> > the wrong cpu, and running on the wrong set of pagetables.
> >
> > At best, you will copy bogus data from the wrong process/domain, and
> > likely corrupt it when copying back.
> >
> > > + {
> > > + ret = -EFAULT;
> > > + break;
> > > + }
> > > +
> > > + if ( data.rsvd ) {
>
> That '{' needs to be on its own line.
>
> > > + ret = -EINVAL;
> > > + break;
> > > + }
> > > +
> > > + switch ( data.cmd )
> > > + {
> > > + case XEN_RESOURCE_OP_MSR_READ:
> > > + case XEN_RESOURCE_OP_MSR_WRITE:
> > > + if ( data.idx >> 32 )
> > > + ret = -EINVAL;
> > > + else if ( !allow_access_msr(data.idx) )
> > > + ret = -EACCES;
> > > + else if ( data.cmd == XEN_RESOURCE_OP_MSR_READ )
> > > + ret = rdmsr_safe(data.idx, data.val);
> > > + else
> > > + ret = wrmsr_safe(data.idx, data.val);
> > > + break;
> > > + default:
> > > + ret = -EINVAL;
> > > + break;
> > > + }
> > > +
> > > + if ( ret )
> > > + break;
> > > +
> > > + if ( copy_to_guest_offset(ra->data, i, &data, 1) )
> > > + {
> > > + ret = -EFAULT;
> > > + 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 +663,34 @@ 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.nr = rsc_op->nr;
> > > + ra.data = rsc_op->data;
> >
> > You must do all copy_{from,to}_user() here, and strictly only pass Xen
> > pointers to resource_access().
> >
> > This means you will need to xmalloc() yourself some space for the
> > xenpf_resource_data_t array.
> >
> >
> > On a different note, you need to enforce a maximum resource_op.nr of
> > something rather low to (16/32 perhaps?) to prevent a toolstack asking
> > for 0xffffffff non-preemptible operations.
>
> The toolstack has:
>
> int xc_resource_op(xc_interface *xch, uint32_t nr_ops, xc_resource_op_t *ops)
> {
> if ( nr_ops == 1 )
> return xc_resource_op_one(xch, ops);
>
> And with that expectation we ought to have a similar check here, in the form
> of:
>
> if ( ra.nr != 1 )
> return -EINVAL;
>
The 'nr' here is not the 'nr_ops', but the 'nr_entries' contained in an 'op'.
This hypercall can only process only one 'op' at a time, multiple 'ops'
are processed by multicall then pass each 'op' down to this hypercall.
While I think I can improve the name here(nr => nr_entries).
Thanks.
> >
> > ~Andrew
> >
> > > +
> > > + if ( rsc_op->cpu == cpu )
> > > + resource_access(&ra);
> > > + else if ( cpu_online(rsc_op->cpu) )
> > > + on_selected_cpus(cpumask_of(rsc_op->cpu),
> > > + resource_access, &ra, 1);
> > > + else
> > > + {
> > > + ret = -ENODEV;
> > > + break;
> > > + }
> > > +
> > > + if ( ra.ret )
> > > + {
> > > + ret = ra.ret;
> > > + break;
> > > + }
> > > + }
> > > + break;
> > > +
> > > default:
> > > ret = -ENOSYS;
> > > break;
> > > diff --git a/xen/arch/x86/x86_64/platform_hypercall.c
> > > b/xen/arch/x86/x86_64/platform_hypercall.c
> > > index b6f380e..4db6622 100644
> > > --- a/xen/arch/x86/x86_64/platform_hypercall.c
> > > +++ b/xen/arch/x86/x86_64/platform_hypercall.c
> > > @@ -32,6 +32,10 @@ CHECK_pf_pcpu_version;
> > > CHECK_pf_enter_acpi_sleep;
> > > #undef xen_pf_enter_acpi_sleep
> > >
> > > +#define xen_pf_resource_data xenpf_resource_data
> > > +CHECK_pf_resource_data;
> > > +#undef xen_pf_resource_data
> > > +
> > > #define COMPAT
> > > #define _XEN_GUEST_HANDLE(t) XEN_GUEST_HANDLE(t)
> > > #define _XEN_GUEST_HANDLE_PARAM(t) XEN_GUEST_HANDLE_PARAM(t)
> > > diff --git a/xen/include/public/platform.h b/xen/include/public/platform.h
> > > index 053b9fa..e4d9091 100644
> > > --- a/xen/include/public/platform.h
> > > +++ b/xen/include/public/platform.h
> > > @@ -527,6 +527,28 @@ 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
>
> More details please.
ok
> > > +
> > > +#define XEN_RESOURCE_OP_MSR_READ 0
> > > +#define XEN_RESOURCE_OP_MSR_WRITE 1
> > > +
> > > +struct xenpf_resource_data {
> > > + uint32_t cmd; /* XEN_RESOURCE_OP_* */
> > > + uint32_t rsvd;
> > > + uint64_t idx;
> > > + uint64_t val;
>
> More details please. Pls say what the 'rsvd' is for, what
> the expected values are for 'idx', and 'val'.
>
> Do also say which ones are IN or OUT.
>
> Put yourself in the mindset of somebody who wants to use this
> and does not want to dive in the hypervisor to figure this out.
> Give as much information as possible in the headers.
>
Good suggestion, I will follow this.
> > > +typedef struct xenpf_resource_data xenpf_resource_data_t;
> > > +DEFINE_XEN_GUEST_HANDLE(xenpf_resource_data_t);
> > > +
> > > +struct xenpf_resource_op {
> > > + uint32_t nr; /* number of data entry */
> > > + uint32_t cpu; /* which cpu to run */
> > > + XEN_GUEST_HANDLE(xenpf_resource_data_t) data;
> > > +};
> > > +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 +575,7 @@ 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;
>
> resource_op? I would really call this 'msr' or 'msr_data'
So you have known that this is not just for msr.
>
>
> > > uint8_t pad[128];
> > > } u;
> > > };
> > > diff --git a/xen/include/xlat.lst b/xen/include/xlat.lst
> > > index 9a35dd7..100fcf5 100644
> > > --- a/xen/include/xlat.lst
> > > +++ b/xen/include/xlat.lst
> > > @@ -88,6 +88,8 @@
> > > ? xenpf_enter_acpi_sleep platform.h
> > > ? xenpf_pcpuinfo platform.h
> > > ? xenpf_pcpu_version platform.h
> > > +? xenpf_resource_op platform.h
> > > +? xenpf_resource_data platform.h
> > > ! sched_poll sched.h
> > > ? sched_remote_shutdown sched.h
> > > ? sched_shutdown sched.h
> >
> >
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