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KVM: arm64: Fix timer offsets for non-protected VMs

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With pKVM, protected VMs always have offset of zero.
However, timer offsets for non-protected guests fail to take effect
for two reasons:
1) In __timer_enable_traps(), enabling of traps check for
   is_protected_kvm_enabled() rather than vcpu_is_protected(vcpu)

2) The vcpu timer offsets were never initialised and kept as NULL.

This is problematic for cases when the timer is trapped in the
hypervisor as the with the case of broken CNTVOFF_EL2, which leads
to the hypervisor and host using different offsets and causing VM
hangs.

This can be confirmed by running the arch_timer selftest which fails:
./arch_timer -o 100000000
Random seed: 0x6b8b4567
Guest assert failed,  vcpu 0; stage; 3; iter: 0
==== Test Assertion Failure ====
  arm64/arch_timer.c:137: config_iter + 1 == irq_iter
  pid=310 tid=312 errno=4 - Interrupted system call
Guest assert failed,  vcpu 3; stage; 3; iter: 0
Guest assert failed,  vcpu 1; stage; 3; iter: 0
==== Test Assertion Failure ====
  arm64/arch_timer.c:137: config_iter + 1 == irq_iter
  pid=310 tid=313 errno=4 - Interrupted system call
Guest assert failed,  vcpu 2; stage; 3; iter: 0
==== Test Assertion Failure ====
  arm64/arch_timer.c:137: config_iter + 1 == irq_iter
  pid=310 tid=314 errno=4 - Interrupted system call
[...]

After the fix:

./arch_timer -o 100000000
Random seed: 0x6b8b4567
PASS(vCPU-1).
PASS(vCPU-3).
PASS(vCPU-0).
PASS(vCPU-2)

Reported-by: Sashiko <sashiko-bot@kernel.org>
Fixes: cb0c272ace ("KVM: arm64: Initialize the hypervisor's VM state at EL2")
Signed-off-by: Mostafa Saleh <smostafa@google.com>
Link: https://patch.msgid.link/20260808085824.732659-3-smostafa@google.com
Signed-off-by: Oliver Upton <oupton@kernel.org>
This commit is contained in:
Mostafa Saleh 2026-08-08 08:58:23 +00:00 • committed by Oliver Upton
commit 47d3eef780
2 changed files with 17 additions and 3 deletions
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