Hi,
On 12/11/26 6:39 PM, Shrikanth Hegde wrote:
After applying preempt disable patch, i.e PATCH 2/3, Christian reported
a subsequent warning stopping his board to boot properly.
WARNING: at .kvmppc_fix_ee_before_entry+0x10/0x28, CPU#0: qemu-system-ppc/4667
CPU: 0 UID: 1000 PID: 4667 Comm: qemu-system-ppc Tainted: G W
7.3.0-rc4-2-powerpc64-smp #1 PREEMPT
Tainted: [W]=WARN
Hardware name: varisys,CYRUS5040 e5500 0x80240012 CoreNet Generic
NIP [c00000000005dc3c] .kvmppc_fix_ee_before_entry+0x10/0x28
LR [c00000000005f298] .kvmppc_handle_exit+0x5b4/0x5e8
Call Trace:
[c000000086587780] [c00000000005ee10] .kvmppc_handle_exit+0x12c/0x5e8
(unreliable)
[c000000086587830] [c000000000062068] .kvmppc_resume_host+0xb8/0x10c
It triggers below warning...
static inline void kvmppc_fix_ee_before_entry(void)
{
trace_hardirqs_on();
/*
* To avoid races, the caller must have gone directly from having
* interrupts fully-enabled to hard-disabled.
*/
WARN_ON(local_paca->irq_happened != PACA_IRQ_HARD_DIS);
This happens since kvmppc_prepare_to_enter does first local_irq_disable
followed by hard_irq_disable. This leaves a small window where interrupt
may occur and it could set the irq pending bit in PACA.
That local_irq_disable was necessary for PPC32 to track the lockdep
state etc. On PPC64 hard_irq_disable is good enough. There is no need to
do both. Use the new irq api to do the necessary one.
Fixes: 12013e3d4695 ("KVM: powerpc: Use generic xfer to guest work function")
Reported-by: Christian Zigotzky<[email protected]>
Closes:https://lore.kernel.org/all/b8f82519-9ae5-c247-e020-
[email protected]/
Tested-by: Christian Zigotzky<[email protected]>
Reviewed-by: Mukesh Kumar Chaurasiya (IBM)<[email protected]>
Signed-off-by: Shrikanth Hegde<[email protected]>
---
arch/powerpc/kvm/booke.c | 3 +--
arch/powerpc/kvm/powerpc.c | 14 +++-----------
2 files changed, 4 insertions(+), 13 deletions(-)
diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index aed7b476b7eb..1ba28848e8bc 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -722,8 +722,7 @@ int kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
if (vcpu->arch.shared->msr & MSR_WE) {
local_irq_enable();
kvm_vcpu_halt(vcpu);
- local_irq_disable();
- hard_irq_disable();
+ ppc_hard_irq_disable();
kvmppc_set_exit_type(vcpu, EMULATED_MTMSRWE_EXITS);
r = 1;
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 9194cf492d1c..4ee3d7bfe917 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -81,13 +81,7 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
int r;
WARN_ON(irqs_disabled());
- /*
- * local_irq_disable() first: on 32-bit, hard_irq_disable() alone is a
- * raw MSR[EE] clear that bypasses the lockdep/irq-tracing state, and
- * the xfer_to_guest_mode helpers assert IRQs are seen as disabled.
- */
- local_irq_disable();
- hard_irq_disable();
+ ppc_hard_irq_disable();
while (true) {
xfer_to_guest_mode_prepare();
@@ -101,8 +95,7 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
*/
local_irq_enable();
r = kvm_xfer_to_guest_mode_handle_work(vcpu);
- local_irq_disable();
- hard_irq_disable();
+ ppc_hard_irq_disable();
if (r) {
/*
* The generic helper does not set the exit
@@ -134,8 +127,7 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
local_irq_enable();
trace_kvm_check_requests(vcpu);
r = kvmppc_core_check_requests(vcpu);
- local_irq_disable();
- hard_irq_disable();
+ ppc_hard_irq_disable();
if (r > 0)
continue;
break;
The changes look good to me.
Using ppc_hard_irq_disable() directly on PPC64 avoids the soft-disable
to hard-disable window, while preserving the software IRQ mask and
tracing state required by the guest-entry path. The BookE halt path and
the guest-work retry paths are covered as well.
Reviewed-by: Narayana Murty N [email protected]
