Commit 290a6bb0 authored by Andrew Jones's avatar Andrew Jones Committed by Marc Zyngier
Browse files

arm64: KVM: Add UAPI notes for swapped registers 



Two UAPI system register IDs do not derive their values from the
ARM system register encodings. This is because their values were
accidentally swapped. As the IDs are API, they cannot be changed.
Add WARNING notes to point them out.

Suggested-by: default avatarMarc Zyngier <maz@kernel.org>
Signed-off-by: default avatarAndrew Jones <drjones@redhat.com>
[maz: turned XXX into WARNING]
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200120130825.28838-1-drjones@redhat.com
parent 0e20f5e2

Documentation/virt/kvm/api.txt

+9 −0
Original line number Diff line number Diff line
@@ -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>

arch/arm64/include/uapi/asm/kvm.h

+10 −2
Original line number Diff line number Diff line
@@ -220,10 +220,18 @@ struct kvm_vcpu_events { 
#define KVM_REG_ARM_PTIMER_CVAL		ARM64_SYS_REG(3, 3, 14, 2, 2)

#define KVM_REG_ARM_PTIMER_CNT		ARM64_SYS_REG(3, 3, 14, 0, 1)



/* EL0 Virtual Timer Registers */

/*

 * EL0 Virtual Timer Registers

 *

 * WARNING:

 *      KVM_REG_ARM_TIMER_CVAL and KVM_REG_ARM_TIMER_CNT are not defined

 *      with the appropriate register encodings.  Their values have been

 *      accidentally swapped.  As this is set API, the definitions here

 *      must be used, rather than ones derived from the encodings.

 */

#define KVM_REG_ARM_TIMER_CTL		ARM64_SYS_REG(3, 3, 14, 3, 1)

#define KVM_REG_ARM_TIMER_CNT		ARM64_SYS_REG(3, 3, 14, 3, 2)

#define KVM_REG_ARM_TIMER_CVAL		ARM64_SYS_REG(3, 3, 14, 0, 2)

#define KVM_REG_ARM_TIMER_CNT		ARM64_SYS_REG(3, 3, 14, 3, 2)



/* KVM-as-firmware specific pseudo-registers */

#define KVM_REG_ARM_FW			(0x0014 << KVM_REG_ARM_COPROC_SHIFT)

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