When receiving an INIT, a prior bugfix tried to ignore the INIT and continue
onwards.
Unfortunately it's not safe to return at that point in vmx_vmexit_handler().
Just out of context in the first hunk is a local_irqs_enabled() which is
depended-upon by the return-to-guest path, causing the following checklock
failure in debug builds:
(XEN) Error: INIT received - ignoring
(XEN) CHECKLOCK FAILURE: prev irqsafe: 0, curr irqsafe 1
(XEN) Xen BUG at common/spinlock.c:132
(XEN) ----[ Xen-4.19-unstable x86_64 debug=y Tainted: H ]----
...
(XEN) Xen call trace:
(XEN) [<ffff82d040238e10>] R check_lock+0xcd/0xe1
(XEN) [<ffff82d040238fe3>] F _spin_lock+0x1b/0x60
(XEN) [<ffff82d0402ed6a8>] F pt_update_irq+0x32/0x3bb
(XEN) [<ffff82d0402b9632>] F vmx_intr_assist+0x3b/0x51d
(XEN) [<ffff82d040206447>] F vmx_asm_vmexit_handler+0xf7/0x210
Luckily, this is benign in release builds. Accidentally having IRQs disabled
when trying to take an IRQs-on lock isn't a deadlock-vulnerable pattern.
Drop the problematic early return. In hindsight, it's wrong to skip other
normal VMExit steps.
Fixes: b1f11273d5a7 ("x86/vmx: Don't spuriously crash the domain when INIT is
received")
Reported-by: Reima ISHII <[email protected]>
Signed-off-by: Andrew Cooper <[email protected]>
---
CC: Jan Beulich <[email protected]>
CC: Roger Pau Monné <[email protected]>
CC: Wei Liu <[email protected]>
CC: Jun Nakajima <[email protected]>
CC: Kevin Tian <[email protected]>
CC: Tamas K Lengyel <[email protected]>
CC: Reima Ishii <[email protected]>
CC: Takahiro Shinagawa <[email protected]>
CC: George Dunlap <[email protected]>
With this patch in place, the INIT is ignored and the guest continues:
(XEN) HVM1 restore: CPU 0
(d1) --- Xen Test Framework ---
(d1) Environment: HVM 64bit (Long mode 4 levels)
(XEN) Error: INIT received - ignoring
(d1) Test result: SUCCESS
v2:
* Leave the printk() early, and skip in the main block.
---
xen/arch/x86/hvm/vmx/vmx.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 829c27f1fa33..a85394232a23 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -4090,7 +4090,7 @@ void asmlinkage vmx_vmexit_handler(struct cpu_user_regs
*regs)
case EXIT_REASON_INIT:
printk(XENLOG_ERR "Error: INIT received - ignoring\n");
- return; /* Renter the guest without further processing */
+ break;
}
/* Now enable interrupts so it's safe to take locks. */
@@ -4692,6 +4692,7 @@ void asmlinkage vmx_vmexit_handler(struct cpu_user_regs
*regs)
break;
case EXIT_REASON_EXTERNAL_INTERRUPT: /* Handled earlier */
+ case EXIT_REASON_INIT: /* Handled earlier */
case EXIT_REASON_TPR_BELOW_THRESHOLD: /* Handled later in
vmx_intr_assist() */
case EXIT_REASON_BUS_LOCK: /* Nothing to do (rate-limit only) */
break;
--
2.30.2
