Re: [Xen-devel] [PATCH v3 4/7] sysctl: Add sysctl interface for querying PCI topology

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 02/10/2015 06:13 AM, Andrew Cooper wrote:
> On 09/02/15 20:04, Boris Ostrovsky wrote:
> > Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> > ---
> >   xen/common/sysctl.c         |   73 +++++++++++++++++++++++++++++++++++++++++++
> >   xen/include/public/sysctl.h |   29 +++++++++++++++++
> >   2 files changed, 102 insertions(+), 0 deletions(-)
> >
> > diff --git a/xen/common/sysctl.c b/xen/common/sysctl.c
> > index 30c5806..ea6557f 100644
> > --- a/xen/common/sysctl.c
> > +++ b/xen/common/sysctl.c
> > @@ -384,7 +384,80 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xen_sysctl_t) 
> > u_sysctl)
> >           xfree(cputopo);
> >       }
> >       break;
> > +#ifdef HAS_PCI
> > +    case XEN_SYSCTL_pcitopoinfo:
> > +    {
> > +        xen_sysctl_pcitopoinfo_t *ti = &op->u.pcitopoinfo;
> > +        physdev_pci_device_t *devs;
> > +        uint8_t *nodes;
> > +        unsigned int first_dev, i;
> > +        int num_devs;
> > +
> > +        num_devs = ti->num_devs - ti->first_dev;
> > +
> > +        if ( guest_handle_is_null(ti->devs) ||
> > +             guest_handle_is_null(ti->nodes) ||
> > +             (num_devs <= 0) )
> > +        {
> > +            ret = -EINVAL;
> > +            break;
> > +        }
> > +
> > +        devs = xmalloc_array(physdev_pci_device_t, num_devs);
> > +        nodes = xmalloc_array(uint8_t, num_devs);
> You can do all of this without any memory allocation at all, which will
> simplify your error handling substantially.
>
> Something along the lines of
>
> for(...)
> {
>      copy one physdev_pci_device_t from the guest
>
>      do the lookup
>
>      copy one node id back to the guest
> }
I am trying to avoid doing multiple copies. For lots of devices (IIRC, 
you said you had a system with a few thousand), having two copies per 
loop will add up, I think.
If you look at changes to cputopolgy and numatopology in earlier patch 
(the one you said you'd postpone reviewing until I split the third 
patch) I you will see that I did the same thing there.

-boris

> ~Andrew
>
> > +        if ( !devs || !nodes )
> > +        {
> > +            xfree(devs);
> > +            xfree(nodes);
> > +            ret = -ENOMEM;
> > +            break;
> > +        }
> > +
> > +        first_dev = ti->first_dev;
> > +
> > +        if ( copy_from_guest_offset(devs, ti->devs, first_dev, num_devs) )
> > +        {
> > +            xfree(devs);
> > +            xfree(nodes);
> > +            ret = -EFAULT;
> > +            break;
> > +        }
> >   
> > +        for ( i = 0; i < num_devs; i++ )
> > +        {
> > +            struct pci_dev *pdev;
> > +
> > +            spin_lock(&pcidevs_lock);
> > +            pdev = pci_get_pdev(devs[i].seg, devs[i].bus, devs[i].devfn);
> > +            if ( !pdev || (pdev->node == NUMA_NO_NODE) )
> > +                nodes[i] = INVALID_NODE_ID;
> > +            else
> > +                nodes[i] = pdev->node;
> > +            spin_unlock(&pcidevs_lock);
> > +
> > +            if ( hypercall_preempt_check() )
> > +                break;
> > +        }
> > +
> > +        ti->first_dev += i + 1;
> > +
> > +        if ( __copy_field_to_guest(u_sysctl, op,
> > +                                   u.pcitopoinfo.first_dev) ||
> > +             copy_to_guest_offset(ti->nodes, first_dev, nodes,num_devs) )
> > +        {
> > +            ret = -EFAULT;
> > +            break;
> > +        }
> > +
> > +        if ( ti->first_dev < ti->num_devs )
> > +            ret = hypercall_create_continuation(__HYPERVISOR_sysctl,
> > +                                               "h", u_sysctl);
> > +
> > +        xfree(devs);
> > +        xfree(nodes);
> > +    }
> > +    break;
> > +#endif
> >   #ifdef TEST_COVERAGE
> >       case XEN_SYSCTL_coverage_op:
> >           ret = sysctl_coverage_op(&op->u.coverage_op);
> > diff --git a/xen/include/public/sysctl.h b/xen/include/public/sysctl.h
> > index 7c78f81..044c3a1 100644
> > --- a/xen/include/public/sysctl.h
> > +++ b/xen/include/public/sysctl.h
> > @@ -33,6 +33,7 @@
> >   
> >   #include "xen.h"
> >   #include "domctl.h"
> > +#include "physdev.h"
> >   
> >   #define XEN_SYSCTL_INTERFACE_VERSION 0x0000000C
> >   
> > @@ -494,6 +495,32 @@ struct xen_sysctl_cputopoinfo {
> >   typedef struct xen_sysctl_cputopoinfo xen_sysctl_cputopoinfo_t;
> >   DEFINE_XEN_GUEST_HANDLE(xen_sysctl_cputopoinfo_t);
> >   
> > +/* XEN_SYSCTL_pcitopoinfo */
> > +struct xen_sysctl_pcitopoinfo {
> > +    /* IN: Size of pcitopo array */
> > +    uint32_t num_devs;
> > +
> > +    /*
> > +     * IN/OUT: First element of pcitopo array that needs to be processed by
> > +     * hypervisor.
> > +     * This is used primarily by hypercall continuations and callers will
> > +     * typically set it to zero
> > +     */
> > +    uint32_t first_dev;
> > +
> > +    /* IN: list of devices */
> > +    XEN_GUEST_HANDLE_64(physdev_pci_device_t) devs;
> > +
> > +    /*
> > +     * OUT: node identifier for each device.
> > +     * If information for a particular device is not avalable then set
> > +     * to INVALID_NODE_ID.
> > +     */
> > +    XEN_GUEST_HANDLE_64(uint8) nodes;
> > +};
> > +typedef struct xen_sysctl_pcitopoinfo xen_sysctl_pcitopoinfo_t;
> > +DEFINE_XEN_GUEST_HANDLE(xen_sysctl_pcitopoinfo_t);
> > +
> >   /* XEN_SYSCTL_numainfo */
> >   #define INVALID_MEM_SZ (~0U)
> >   
> > @@ -692,12 +719,14 @@ struct xen_sysctl {
> >   #define XEN_SYSCTL_scheduler_op                  19
> >   #define XEN_SYSCTL_coverage_op                   20
> >   #define XEN_SYSCTL_psr_cmt_op                    21
> > +#define XEN_SYSCTL_pcitopoinfo                   22
> >       uint32_t interface_version; /* XEN_SYSCTL_INTERFACE_VERSION */
> >       union {
> >           struct xen_sysctl_readconsole       readconsole;
> >           struct xen_sysctl_tbuf_op           tbuf_op;
> >           struct xen_sysctl_physinfo          physinfo;
> >           struct xen_sysctl_cputopoinfo       cputopoinfo;
> > +        struct xen_sysctl_pcitopoinfo       pcitopoinfo;
> >           struct xen_sysctl_numainfo          numainfo;
> >           struct xen_sysctl_sched_id          sched_id;
> >           struct xen_sysctl_perfc_op          perfc_op;

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