[PATCH] Deprecate pmem=on with non-DAX capable backend file

[Eduardo Habkost]

On Tue, Apr 27, 2021 at 04:48:48PM -0400, Eduardo Habkost wrote:
> On Mon, Jan 11, 2021 at 03:33:32PM -0500, Igor Mammedov wrote:
> > It is not safe to pretend that emulated NVDIMM supports
> > persistence while backend actually failed to enable it
> > and used non-persistent mapping as fall back.
> > Instead of falling-back, QEMU should be more strict and
> > error out with clear message that it's not supported.
> > So if user asks for persistence (pmem=on), they should
> > store backing file on NVDIMM.
> > 
> > Signed-off-by: Igor Mammedov <imammedo at redhat.com>
> > Reviewed-by: Philippe Mathieu-Daudé <philmd at redhat.com>
> 
> I'm queueing this for 6.1, after changing "since 6.0" to "since 6.1".
> 
> Sorry for letting it fall through the cracks.

This caused build failures[1] and I had to apply the following
fixup.

[1] https://gitlab.com/ehabkost/qemu/-/jobs/1216917482#L3444

Signed-off-by: Eduardo Habkost <ehabkost at redhat.com>
---
 docs/system/deprecated.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/docs/system/deprecated.rst b/docs/system/deprecated.rst
index cc8d810be1a..c55c4bceb00 100644
--- a/docs/system/deprecated.rst
+++ b/docs/system/deprecated.rst
@@ -257,6 +257,7 @@ is (a) not DAX capable or (b) not on a filesystem that support direct mapping
 of persistent memory, is not safe and may lead to data loss or corruption in case
 of host crash.
 Options are:
+
     - modify VM configuration to set ``pmem=off`` to continue using fake NVDIMM
       (without persistence guaranties) with backing file on non DAX storage
     - move backing file to NVDIMM storage and keep ``pmem=on``
-- 
2.30.2

-- 
Eduardo