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Date:   Wed, 22 Jul 2020 11:40:34 -0700
From:   Stephen Hemminger <stephen@networkplumber.org>
To:     "Andres Beltran" <lkmlabelt@gmail.com>
Cc:     "Andres Beltran" <t-mabelt@microsoft.com>,
        "KY Srinivasan" <kys@microsoft.com>,
        "Haiyang Zhang" <haiyangz@microsoft.com>,
        "Stephen Hemminger" <sthemmin@microsoft.com>, <wei.liu@kernel.org>,
        <linux-hyperv@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        "Michael Kelley" <mikelley@microsoft.com>,
        <parri.andrea@gmail.com>,
        "James E . J . Bottomley" <jejb@linux.ibm.com>,
        "Martin K . Petersen" <martin.petersen@oracle.com>,
        "David S . Miller" <davem@davemloft.net>
Subject: Re: [PATCH v5 0/3] Drivers: hv: vmbus: vmbus_requestor data
 structure for VMBus hardening
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In-Reply-To: <20200722181051.2688-1-lkmlabelt@gmail.com>
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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.