Re: [Qemu-devel] [PATCH v4 18/29] vhost+postcopy: Resolve client address

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Marc-André Lureau (marcandre.lureau@gmail.com) wrote:
> Hi
> 
> On Thu, Mar 8, 2018 at 8:58 PM, Dr. David Alan Gilbert (git)
> <dgilbert@redhat.com> wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> >
> > Resolve fault addresses read off the clients UFD into RAMBlock
> > and offset, and call back to the postcopy code to ask for the page.
> >
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > Reviewed-by: Peter Xu <peterx@redhat.com>
> 
> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

Thanks,

> 
> > ---
> >  hw/virtio/trace-events |  3 +++
> >  hw/virtio/vhost-user.c | 31 ++++++++++++++++++++++++++++++-
> >  2 files changed, 33 insertions(+), 1 deletion(-)
> >
> > diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
> > index d7e9e1084b..3afd12cfea 100644
> > --- a/hw/virtio/trace-events
> > +++ b/hw/virtio/trace-events
> > @@ -7,6 +7,9 @@ vhost_region_add_section_abut(const char *name, uint64_t new_size) "%s: 0x%"PRIx
> >  vhost_section(const char *name, int r) "%s:%d"
> >
> >  # hw/virtio/vhost-user.c
> > +vhost_user_postcopy_fault_handler(const char *name, uint64_t fault_address, int nregions) "%s: @0x%"PRIx64" nregions:%d"
> > +vhost_user_postcopy_fault_handler_loop(int i, uint64_t client_base, uint64_t size) "%d: client 0x%"PRIx64" +0x%"PRIx64
> > +vhost_user_postcopy_fault_handler_found(int i, uint64_t region_offset, uint64_t rb_offset) "%d: region_offset: 0x%"PRIx64" rb_offset:0x%"PRIx64
> >  vhost_user_postcopy_listen(void) ""
> >  vhost_user_set_mem_table_postcopy(uint64_t client_addr, uint64_t qhva, int reply_i, int region_i) "client:0x%"PRIx64" for hva: 0x%"PRIx64" reply %d region %d"
> >  vhost_user_set_mem_table_withfd(int index, const char *name, uint64_t memory_size, uint64_t guest_phys_addr, uint64_t userspace_addr, uint64_t offset) "%d:%s: size:0x%"PRIx64" GPA:0x%"PRIx64" QVA/userspace:0x%"PRIx64" RB offset:0x%"PRIx64
> > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> > index fd65616961..e19b9ef9cf 100644
> > --- a/hw/virtio/vhost-user.c
> > +++ b/hw/virtio/vhost-user.c
> > @@ -26,6 +26,7 @@
> >  #include <sys/socket.h>
> >  #include <sys/un.h>
> >  #include <linux/vhost.h>
> > +#include <linux/userfaultfd.h>
> >
> >  #define VHOST_MEMORY_MAX_NREGIONS    8
> >  #define VHOST_USER_F_PROTOCOL_FEATURES 30
> > @@ -974,7 +975,35 @@ out:
> >  static int vhost_user_postcopy_fault_handler(struct PostCopyFD *pcfd,
> >                                               void *ufd)
> >  {
> > -    return 0;
> > +    struct vhost_dev *dev = pcfd->data;
> > +    struct vhost_user *u = dev->opaque;
> > +    struct uffd_msg *msg = ufd;
> > +    uint64_t faultaddr = msg->arg.pagefault.address;
> > +    RAMBlock *rb = NULL;
> > +    uint64_t rb_offset;
> > +    int i;
> > +
> > +    trace_vhost_user_postcopy_fault_handler(pcfd->idstr, faultaddr,
> > +                                            dev->mem->nregions);
> > +    for (i = 0; i < MIN(dev->mem->nregions, u->region_rb_len); i++) {
> > +        trace_vhost_user_postcopy_fault_handler_loop(i,
> > +                u->postcopy_client_bases[i], dev->mem->regions[i].memory_size);
> > +        if (faultaddr >= u->postcopy_client_bases[i]) {
> > +            /* Ofset of the fault address in the vhost region */
> > +            uint64_t region_offset = faultaddr - u->postcopy_client_bases[i];
> > +            if (region_offset < dev->mem->regions[i].memory_size) {
> > +                rb_offset = region_offset + u->region_rb_offset[i];
> 
> It may be worth to add an assert (i < u->region_rb_len) ?

The loop limit guarantees that anyway with the 2nd term of the
MIN.

Dave

> 
> > +                trace_vhost_user_postcopy_fault_handler_found(i,
> > +                        region_offset, rb_offset);
> > +                rb = u->region_rb[i];
> > +                return postcopy_request_shared_page(pcfd, rb, faultaddr,
> > +                                                    rb_offset);
> > +            }
> > +        }
> > +    }
> > +    error_report("%s: Failed to find region for fault %" PRIx64,
> > +                 __func__, faultaddr);
> > +    return -1;
> >  }
> >
> >  /*
> > --
> > 2.14.3
> >
> >
> 
> 
> 
> -- 
> Marc-André Lureau
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK