Re: Xen PV: Sample new PV driver for buffer sharing between domains

[Juergen Gross <jgross@suse.com>]

On 28/09/2018 14:55, Omkar Bolla wrote:
> Hi,
> I tried to run script after pause the domain and unpause domain after
> run script. But I ended up with same error

I looked at the script again, it is wrong. The permissions should
be set for each node under the root path of the respective domains,
the first permission should be "n$domid" ($domid is the owner who
can always read/write, the n is "no access" for all domains not
explicitly listed), the second permission should be "r$domid" as
the other side should be able to read only.

In order to do it correctly the script should be:

#!/bin/bash

DOMU_ID=$1

if [ -z "$DOMU_ID"  ]; then
  echo "Usage: $0 [domU ID]]"
  echo
  echo "Connects the new device, with dom0 as backend, domU as frontend"
  exit 1
fi

# Pause domU as a script can't write an entry and set permission
# in a single operation.
xl pause $DOMU_ID

DEVICE=mydevice
DOMU_KEY=/local/domain/$DOMU_ID/device/$DEVICE/0
DOM0_KEY=/local/domain/0/backend/$DEVICE/$DOMU_ID/0

# Tell the domU about the new device and its backend
xenstore-write $DOMU_KEY/backend-id 0
xenstore-write $DOMU_KEY/backend
"/local/domain/0/backend/$DEVICE/$DOMU_ID/0"

# Tell the dom0 about the new device and its frontend
xenstore-write $DOM0_KEY/frontend-id $DOMU_ID
xenstore-write $DOM0_KEY/frontend "/local/domain/$DOMU_ID/device/$DEVICE/0"

# Activate the device, dom0 needs to be activated last
xenstore-write $DOMU_KEY/state 1
xenstore-write $DOM0_KEY/state 1

# Make sure the domU can read the dom0 data
xenstore-chmod -r $DOM0_KEY n0 r$DOMU_ID
xenstore-chmod -r $DOMU_KEY n$DOMU_ID r0

xl unpause $DOMU_ID


Juergen

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