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

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(a)redhat.com&gt; > > Reviewed-by: Philippe Mathieu-Daudé <philmd(a)redhat.com&gt; > > 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(a)redhat.com&gt; --- 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``