RE: [PATCH v5 0/3] Drivers: hv: vmbus: vmbus_requestor data structure for VMBus hardening

[Michael Kelley <mikelley@microsoft.com>]

From: Stephen Hemminger <stephen@networkplumber.org> Sent: Wednesday, July 22, 2020 11:41 AM
> 
> On Wed, 22 Jul 2020 11:10:48 -0700
> "Andres Beltran" <lkmlabelt@gmail.com> wrote:
> 
> > Currently, VMbus drivers use pointers into guest memory as request IDs
> > for interactions with Hyper-V. To be more robust in the face of errors
> > or malicious behavior from a compromised Hyper-V, avoid exposing
> > guest memory addresses to Hyper-V. Also avoid Hyper-V giving back a
> > bad request ID that is then treated as the address of a guest data
> > structure with no validation. Instead, encapsulate these memory
> > addresses and provide small integers as request IDs.
> >
> > The first patch creates the definitions for the data structure, provides
> > helper methods to generate new IDs and retrieve data, and
> > allocates/frees the memory needed for vmbus_requestor.
> >
> > The second and third patches make use of vmbus_requestor to send request
> > IDs to Hyper-V in storvsc and netvsc respectively.
> >
> > Thanks.
> > Andres Beltran
> >
> > Cc: James E.J. Bottomley <jejb@linux.ibm.com>
> > Cc: Martin K. Petersen <martin.petersen@oracle.com>
> > Cc: David S. Miller <davem@davemloft.net>
> >
> > Andres Beltran (3):
> >   Drivers: hv: vmbus: Add vmbus_requestor data structure for VMBus
> >     hardening
> >   scsi: storvsc: Use vmbus_requestor to generate transaction IDs for
> >     VMBus hardening
> >   hv_netvsc: Use vmbus_requestor to generate transaction IDs for VMBus
> >     hardening
> >
> >  drivers/hv/channel.c              | 175 ++++++++++++++++++++++++++++++
> >  drivers/net/hyperv/hyperv_net.h   |  13 +++
> >  drivers/net/hyperv/netvsc.c       |  79 +++++++++++---
> >  drivers/net/hyperv/rndis_filter.c |   1 +
> >  drivers/scsi/storvsc_drv.c        |  85 +++++++++++++--
> >  include/linux/hyperv.h            |  22 ++++
> >  6 files changed, 350 insertions(+), 25 deletions(-)
> >
> 
> 
> What is the performance impact of this?
> It means keeping a global (bookkeeping) structure which should have
> noticeable impact on mult-queue performance.

The bookkeeping structure is per-VMbus channel.  There's nothing
global.   Andrea Parri previously did some testing and reported no
measurable impact.

Michael