Re: [libvirt] [PATCH] libxl: always enable pae for x86_64 HVM

[Jim Fehlig]

On 01/12/2017 07:34 AM, Daniel P. Berrange wrote:
On Thu, Jan 12, 2017 at 07:31:29AM -0700, Jim Fehlig wrote:
On 01/12/2017 02:06 AM, Martin Kletzander wrote:
On Wed, Jan 11, 2017 at 05:45:27PM -0700, Jim Fehlig wrote:
For HVM domains, pae is only set in libxl_domain_build_info when
explicitly specified in the hypervisor <features> config. This is
fine for i686 machines, but is incorrect behavior for x86_64 machines
where pae must always be enabled. See the following discussion for
additional details
https://www.redhat.com/archives/libvir-list/2017-January/msg00254.html
Signed-off-by: Jim Fehlig <jfeh...@suse.com>
---
src/libxl/libxl_domain.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/src/libxl/libxl_domain.c b/src/libxl/libxl_domain.c
index fbe7ee5..a5314b0 100644
--- a/src/libxl/libxl_domain.c
+++ b/src/libxl/libxl_domain.c
@@ -410,6 +410,12 @@ libxlDomainDefPostParse(virDomainDefPtr def,
    if (xenDomainDefAddImplicitInputDevice(def) < 0)
        return -1;

+    /* For x86_64 HVM, always enable pae */
+    if (def->os.type == VIR_DOMAIN_OSTYPE_HVM &&
+        def->os.arch == VIR_ARCH_X86_64) {
+        def->features[VIR_DOMAIN_FEATURE_PAE] = VIR_TRISTATE_SWITCH_ON;
+    }
+

This will even rewrite explicit <pae enabled='no/>

According to docs/schemas/domaincommon.rng, pae is not a tristate :-). One
of the options for solving this problem is to make it one

https://www.redhat.com/archives/libvir-list/2017-January/msg00254.html

Heh, the schema is wrong then, since the code treats all features
the same way, as tri-states :-)

src/conf/domain_conf.c treats them differently. E.g. see the features switch 
statement in the parse function

http://libvirt.org/git/?p=libvirt.git;a=blob;f=src/conf/domain_conf.c;h=52aee2b020c12fd016fc14c1f4d7d2594e170817;hb=HEAD#l16997

# cat test.xml | grep pae
    <pae state='off'/>
# virt-xml-validate test.xml
Relax-NG validity error : Extra element features in interleave
test.xml:19: element features: Relax-NG validity error : Element domain failed 
to validate content
test.xml fails to validate
# virsh define test.xml
Domain test-hvm defined from test.xml

# virsh dumpxml test-hvm | grep pae
    <pae/>

Regards,
Jim

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