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authorJanosch Frank <frankja@linux.ibm.com>2018-08-01 13:48:28 +0300
committerJanosch Frank <frankja@linux.ibm.com>2018-09-12 15:46:37 +0300
commit40ebdb8e59df36e2cc71810bd021a0808b16c956 (patch)
tree636895d9c4298e3c178ee73fc7ff00e1e5345aa0 /Documentation/virtual
parent1843abd03250115af6cec0892683e70cf2297c25 (diff)
downloadlinux-40ebdb8e59df36e2cc71810bd021a0808b16c956.tar.xz
KVM: s390: Make huge pages unavailable in ucontrol VMs
We currently do not notify all gmaps when using gmap_pmdp_xchg(), due to locking constraints. This makes ucontrol VMs, which is the only VM type that creates multiple gmaps, incompatible with huge pages. Also we would need to hold the guest_table_lock of all gmaps that have this vmaddr maped to synchronize access to the pmd. ucontrol VMs are rather exotic and creating a new locking concept is no easy task. Hence we return EINVAL when trying to active KVM_CAP_S390_HPAGE_1M and report it as being not available when checking for it. Fixes: a4499382 ("KVM: s390: Add huge page enablement control") Signed-off-by: Janosch Frank <frankja@linux.ibm.com> Reviewed-by: David Hildenbrand <david@redhat.com> Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com> Message-Id: <20180801112508.138159-1-frankja@linux.ibm.com> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Diffstat (limited to 'Documentation/virtual')
-rw-r--r--Documentation/virtual/kvm/api.txt3
1 files changed, 2 insertions, 1 deletions
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index c664064f76fb..8d8a372c8340 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -4510,7 +4510,8 @@ Do not enable KVM_FEATURE_PV_UNHALT if you disable HLT exits.
Architectures: s390
Parameters: none
Returns: 0 on success, -EINVAL if hpage module parameter was not set
- or cmma is enabled
+ or cmma is enabled, or the VM has the KVM_VM_S390_UCONTROL
+ flag set
With this capability the KVM support for memory backing with 1m pages
through hugetlbfs can be enabled for a VM. After the capability is