From eca5416f9b0e179de9553900de8de660ab09199d Mon Sep 17 00:00:00 2001 From: Andrew Cooper Date: Fri, 2 Feb 2024 08:02:51 +0100 Subject: [PATCH 07/67] x86/vmx: Fix IRQ handling for EXIT_REASON_INIT 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) [] R check_lock+0xcd/0xe1 (XEN) [] F _spin_lock+0x1b/0x60 (XEN) [] F pt_update_irq+0x32/0x3bb (XEN) [] F vmx_intr_assist+0x3b/0x51d (XEN) [] 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 Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich master commit: d1f8883aebe00f6a9632d77ab0cd5c6d02c9cbe4 master date: 2024-01-18 20:59:06 +0000 --- 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 072288a5ef..31f4a861c6 100644 --- a/xen/arch/x86/hvm/vmx/vmx.c +++ b/xen/arch/x86/hvm/vmx/vmx.c @@ -4037,7 +4037,7 @@ void 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. */ @@ -4323,6 +4323,7 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs) break; } case EXIT_REASON_EXTERNAL_INTERRUPT: + case EXIT_REASON_INIT: /* Already handled above. */ break; case EXIT_REASON_TRIPLE_FAULT: -- 2.44.0