mirror of https://gitee.com/openkylin/linux.git
KVM: PPC: Book3S HV: Drop locks before reading guest memory
Running with CONFIG_DEBUG_ATOMIC_SLEEP reveals that HV KVM tries to
read guest memory, in order to emulate guest instructions, while
preempt is disabled and a vcore lock is held. This occurs in
kvmppc_handle_exit_hv(), called from post_guest_process(), when
emulating guest doorbell instructions on POWER9 systems, and also
when checking whether we have hit a hypervisor breakpoint.
Reading guest memory can cause a page fault and thus cause the
task to sleep, so we need to avoid reading guest memory while
holding a spinlock or when preempt is disabled.
To fix this, we move the preempt_enable() in kvmppc_run_core() to
before the loop that calls post_guest_process() for each vcore that
has just run, and we drop and re-take the vcore lock around the calls
to kvmppc_emulate_debug_inst() and kvmppc_emulate_doorbell_instr().
Dropping the lock is safe with respect to the iteration over the
runnable vcpus in post_guest_process(); for_each_runnable_thread
is actually safe to use locklessly. It is possible for a vcpu
to become runnable and add itself to the runnable_threads array
(code near the beginning of kvmppc_run_vcpu()) and then get included
in the iteration in post_guest_process despite the fact that it
has not just run. This is benign because vcpu->arch.trap and
vcpu->arch.ceded will be zero.
Cc: stable@vger.kernel.org # v4.13+
Fixes: 579006944e
("KVM: PPC: Book3S HV: Virtualize doorbell facility on POWER9")
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
This commit is contained in:
parent
9b9b13a6d1
commit
36ee41d161
|
@ -1008,8 +1008,6 @@ static int kvmppc_emulate_doorbell_instr(struct kvm_vcpu *vcpu)
|
|||
struct kvm *kvm = vcpu->kvm;
|
||||
struct kvm_vcpu *tvcpu;
|
||||
|
||||
if (!cpu_has_feature(CPU_FTR_ARCH_300))
|
||||
return EMULATE_FAIL;
|
||||
if (kvmppc_get_last_inst(vcpu, INST_GENERIC, &inst) != EMULATE_DONE)
|
||||
return RESUME_GUEST;
|
||||
if (get_op(inst) != 31)
|
||||
|
@ -1059,6 +1057,7 @@ static int kvmppc_emulate_doorbell_instr(struct kvm_vcpu *vcpu)
|
|||
return RESUME_GUEST;
|
||||
}
|
||||
|
||||
/* Called with vcpu->arch.vcore->lock held */
|
||||
static int kvmppc_handle_exit_hv(struct kvm_run *run, struct kvm_vcpu *vcpu,
|
||||
struct task_struct *tsk)
|
||||
{
|
||||
|
@ -1179,7 +1178,10 @@ static int kvmppc_handle_exit_hv(struct kvm_run *run, struct kvm_vcpu *vcpu,
|
|||
swab32(vcpu->arch.emul_inst) :
|
||||
vcpu->arch.emul_inst;
|
||||
if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) {
|
||||
/* Need vcore unlocked to call kvmppc_get_last_inst */
|
||||
spin_unlock(&vcpu->arch.vcore->lock);
|
||||
r = kvmppc_emulate_debug_inst(run, vcpu);
|
||||
spin_lock(&vcpu->arch.vcore->lock);
|
||||
} else {
|
||||
kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
|
||||
r = RESUME_GUEST;
|
||||
|
@ -1194,8 +1196,13 @@ static int kvmppc_handle_exit_hv(struct kvm_run *run, struct kvm_vcpu *vcpu,
|
|||
*/
|
||||
case BOOK3S_INTERRUPT_H_FAC_UNAVAIL:
|
||||
r = EMULATE_FAIL;
|
||||
if ((vcpu->arch.hfscr >> 56) == FSCR_MSGP_LG)
|
||||
if (((vcpu->arch.hfscr >> 56) == FSCR_MSGP_LG) &&
|
||||
cpu_has_feature(CPU_FTR_ARCH_300)) {
|
||||
/* Need vcore unlocked to call kvmppc_get_last_inst */
|
||||
spin_unlock(&vcpu->arch.vcore->lock);
|
||||
r = kvmppc_emulate_doorbell_instr(vcpu);
|
||||
spin_lock(&vcpu->arch.vcore->lock);
|
||||
}
|
||||
if (r == EMULATE_FAIL) {
|
||||
kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
|
||||
r = RESUME_GUEST;
|
||||
|
@ -2946,13 +2953,14 @@ static noinline void kvmppc_run_core(struct kvmppc_vcore *vc)
|
|||
/* make sure updates to secondary vcpu structs are visible now */
|
||||
smp_mb();
|
||||
|
||||
preempt_enable();
|
||||
|
||||
for (sub = 0; sub < core_info.n_subcores; ++sub) {
|
||||
pvc = core_info.vc[sub];
|
||||
post_guest_process(pvc, pvc == vc);
|
||||
}
|
||||
|
||||
spin_lock(&vc->lock);
|
||||
preempt_enable();
|
||||
|
||||
out:
|
||||
vc->vcore_state = VCORE_INACTIVE;
|
||||
|
|
Loading…
Reference in New Issue