On 2021-02-26 18:12, Will Deacon wrote:
Commit 7db21530479f ("KVM: arm64: Restore hyp when panicking in guest context") tracks the currently running vCPU, clearing the pointer to NULL on exit from a guest.
Unfortunately, the use of 'set_loaded_vcpu' clobbers x1 to point at the kvm_hyp_ctxt instead of the vCPU context, causing the subsequent RAS code to go off into the weeds when it saves the DISR assuming that the CPU context is embedded in a struct vCPU.
Leave x1 alone and use x3 as a temporary register instead when clearing the vCPU on the guest exit path.
Cc: Marc Zyngier maz@kernel.org Cc: Andrew Scull ascull@google.com Cc: stable@vger.kernel.org Fixes: 7db21530479f ("KVM: arm64: Restore hyp when panicking in guest context") Suggested-by: Quentin Perret qperret@google.com Signed-off-by: Will Deacon will@kernel.org
This was pretty awful to debug!
arch/arm64/kvm/hyp/entry.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S index b0afad7a99c6..0c66a1d408fd 100644 --- a/arch/arm64/kvm/hyp/entry.S +++ b/arch/arm64/kvm/hyp/entry.S @@ -146,7 +146,7 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL) // Now restore the hyp regs restore_callee_saved_regs x2
- set_loaded_vcpu xzr, x1, x2
- set_loaded_vcpu xzr, x2, x3
alternative_if ARM64_HAS_RAS_EXTN // If we have the RAS extensions we can consume a pending error
Grmbl... How comes we have never seen that for the past 5 months, including on CPUs that implement RAS?
Thanks,
M.