linux-kernel - Re: [PATCH 0/3] Drivers: hv: vmbus: vmbus

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Date:   Fri, 26 Jun 2020 16:48:17 +0200
From:   Andrea Parri <parri.andrea@...il.com>
To:     Wei Liu <wei.liu@...nel.org>
Cc:     Andres Beltran <lkmlabelt@...il.com>, kys@...rosoft.com,
        haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        mikelley@...rosoft.com, linux-scsi@...r.kernel.org,
        netdev@...r.kernel.org,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH 0/3] Drivers: hv: vmbus: vmbus_requestor data structure

On Fri, Jun 26, 2020 at 01:42:27PM +0000, Wei Liu wrote:
> On Thu, Jun 25, 2020 at 11:37:20AM -0400, Andres Beltran wrote:
> > From: Andres Beltran (Microsoft) <lkmlabelt@...il.com>
> > 
> > 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.
> > 
> 
> Per my understanding, this new data structure is per-channel, so it
> won't introduce contention on the lock in multi-queue scenario. Have you
> done any testing to confirm there is no severe performance regression?

I did run some performance tests using our dev pipeline (storage and
network workloads).  I did not find regressions w.r.t. baseline.

  Andrea