path: root/Documentation/virtual
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authorAlexander Graf <agraf@suse.de>2014-05-12 01:08:32 +0200
committerAlexander Graf <agraf@suse.de>2014-05-30 14:26:24 +0200
commitf3383cf80e417e86fcc84a2eb4c96bc52842d8d9 (patch)
tree69cde42c1f516992ef2e6db665d1098ee0eac951 /Documentation/virtual
parent1f365bb0de12da4a9ef8e56ffba2218d9a026011 (diff)
KVM: PPC: Disable NX for old magic page using guests
Old guests try to use the magic page, but map their trampoline code inside of an NX region. Since we can't fix those old kernels, try to detect whether the guest is sane or not. If not, just disable NX functionality in KVM so that old guests at least work at all. For newer guests, add a bit that we can set to keep NX functionality available. Signed-off-by: Alexander Graf <agraf@suse.de>
Diffstat (limited to 'Documentation/virtual')
1 files changed, 14 insertions, 0 deletions
diff --git a/Documentation/virtual/kvm/ppc-pv.txt b/Documentation/virtual/kvm/ppc-pv.txt
index 4643cde517c4..319560646f32 100644
--- a/Documentation/virtual/kvm/ppc-pv.txt
+++ b/Documentation/virtual/kvm/ppc-pv.txt
@@ -94,10 +94,24 @@ a bitmap of available features inside the magic page.
The following enhancements to the magic page are currently available:
KVM_MAGIC_FEAT_SR Maps SR registers r/w in the magic page
For enhanced features in the magic page, please check for the existence of the
feature before using them!
+Magic page flags
+In addition to features that indicate whether a host is capable of a particular
+feature we also have a channel for a guest to tell the guest whether it's capable
+of something. This is what we call "flags".
+Flags are passed to the host in the low 12 bits of the Effective Address.
+The following flags are currently available for a guest to expose:
+ MAGIC_PAGE_FLAG_NOT_MAPPED_NX Guest handles NX bits correclty wrt magic page
MSR bits

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