From: Oliver Upton oupton@google.com
stable inclusion from stable-5.10.68 commit a957d82b23161f175b124ef30b005a56e84e7ef2 bugzilla: 182671 https://gitee.com/openeuler/kernel/issues/I4EWUH
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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[ Upstream commit 6826c6849b46aaa91300201213701eb861af4ba0 ]
The CPU_ON PSCI call takes a payload that KVM uses to configure a destination vCPU to run. This payload is non-architectural state and not exposed through any existing UAPI. Effectively, we have a race between CPU_ON and userspace saving/restoring a guest: if the target vCPU isn't ran again before the VMM saves its state, the requested PC and context ID are lost. When restored, the target vCPU will be runnable and start executing at its old PC.
We can avoid this race by making sure the reset payload is serviced before userspace can access a vCPU's state.
Fixes: 358b28f09f0a ("arm/arm64: KVM: Allow a VCPU to fully reset itself") Signed-off-by: Oliver Upton oupton@google.com Signed-off-by: Marc Zyngier maz@kernel.org Link: https://lore.kernel.org/r/20210818202133.1106786-3-oupton@google.com Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Chen Jun chenjun102@huawei.com Acked-by: Weilong Chen chenweilong@huawei.com
Signed-off-by: Chen Jun chenjun102@huawei.com --- arch/arm64/kvm/arm.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 6c6d51ab8730..1dc68282c840 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -1214,6 +1214,14 @@ long kvm_arch_vcpu_ioctl(struct file *filp, if (copy_from_user(®, argp, sizeof(reg))) break;
+ /* + * We could owe a reset due to PSCI. Handle the pending reset + * here to ensure userspace register accesses are ordered after + * the reset. + */ + if (kvm_check_request(KVM_REQ_VCPU_RESET, vcpu)) + kvm_reset_vcpu(vcpu); + if (ioctl == KVM_SET_ONE_REG) r = kvm_arm_set_reg(vcpu, ®); else