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| author |   Janosch Frank <frankja@linux.ibm.com> | 2018-08-01 11:48:28 +0100 |
|---|---|---|
| committer | Janosch Frank <frankja@linux.ibm.com> | 2018-09-12 14:46:37 +0200 |
| commit | 40ebdb8e59df36e2cc71810bd021a0808b16c956 (patch) | |
| tree | 636895d9c4298e3c178ee73fc7ff00e1e5345aa0 /Documentation | |
| parent | s390/mm: Check for valid vma before zapping in gmap_discard (diff) | |
| download | linux-dev-40ebdb8e59df36e2cc71810bd021a0808b16c956.tar.xz linux-dev-40ebdb8e59df36e2cc71810bd021a0808b16c956.zip | |
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')
| -rw-r--r-- | Documentation/virtual/kvm/api.txt | 3 |
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 |