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authorAlexey Kardashevskiy <aik@ozlabs.ru>2014-07-19 11:59:34 +0400
committerAlexander Graf <agraf@suse.de>2014-07-28 17:23:16 +0400
commita0840240c0c6bcbac8f0f5db11f95c19aaf9b52f (patch)
tree3b4a2c128db2ff01c5d646780f0e63fc78d84229 /Documentation/virtual
parentb2677b8dd8de0dc1496ede4da09b9dfd59f15cea (diff)
downloadlinux-a0840240c0c6bcbac8f0f5db11f95c19aaf9b52f.tar.xz
KVM: PPC: Book3S: Fix LPCR one_reg interface
Unfortunately, the LPCR got defined as a 32-bit register in the one_reg interface. This is unfortunate because KVM allows userspace to control the DPFD (default prefetch depth) field, which is in the upper 32 bits. The result is that DPFD always get set to 0, which reduces performance in the guest. We can't just change KVM_REG_PPC_LPCR to be a 64-bit register ID, since that would break existing userspace binaries. Instead we define a new KVM_REG_PPC_LPCR_64 id which is 64-bit. Userspace can still use the old KVM_REG_PPC_LPCR id, but it now only modifies those fields in the bottom 32 bits that userspace can modify (ILE, TC and AIL). If userspace uses the new KVM_REG_PPC_LPCR_64 id, it can modify DPFD as well. Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> Signed-off-by: Paul Mackerras <paulus@samba.org> Cc: stable@vger.kernel.org Signed-off-by: Alexander Graf <agraf@suse.de>
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 69553183ef0f..884f819e1908 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1869,7 +1869,8 @@ registers, find a list below:
PPC | KVM_REG_PPC_PID | 64
PPC | KVM_REG_PPC_ACOP | 64
PPC | KVM_REG_PPC_VRSAVE | 32
- PPC | KVM_REG_PPC_LPCR | 64
+ PPC | KVM_REG_PPC_LPCR | 32
+ PPC | KVM_REG_PPC_LPCR_64 | 64
PPC | KVM_REG_PPC_PPR | 64
PPC | KVM_REG_PPC_ARCH_COMPAT 32
PPC | KVM_REG_PPC_DABRX | 32