Merge tag 'kvm-s390-next-5.6-1' of git://git.kernel.org/pub/scm/linux/kernel/git...

[sfrench/cifs-2.6.git] / Documentation / virt / kvm / api.txt

diff --git a/Documentation/virt/kvm/api.txt b/Documentation/virt/kvm/api.txt
index 73448764f544920394033aa8cb4529c90889fc81..c6e1ce5d40de992df7acd2c3782d619fd0838721 100644 (file)
--- a/Documentation/virt/kvm/api.txt
+++ b/Documentation/virt/kvm/api.txt
@@ -2196,6 +2196,15 @@ arm64 CCSIDR registers are demultiplexed by CSSELR value:
 arm64 system registers have the following id bit patterns:
   0x6030 0000 0013 <op0:2> <op1:3> <crn:4> <crm:4> <op2:3>
 
+WARNING:
+     Two system register IDs do not follow the specified pattern.  These
+     are KVM_REG_ARM_TIMER_CVAL and KVM_REG_ARM_TIMER_CNT, which map to
+     system registers CNTV_CVAL_EL0 and CNTVCT_EL0 respectively.  These
+     two had their values accidentally swapped, which means TIMER_CVAL is
+     derived from the register encoding for CNTVCT_EL0 and TIMER_CNT is
+     derived from the register encoding for CNTV_CVAL_EL0.  As this is
+     API, it must remain this way.
+
 arm64 firmware pseudo-registers have the following bit pattern:
   0x6030 0000 0014 <regno:16>