[PATCH 4/8] KVM: PPC: Book3S HV: Ratelimit machine check messages coming from guests

From: Nicholas Piggin <npiggin@gmail.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: kvm-ppc@vger.kernel.org, Nicholas Piggin <npiggin@gmail.com>,
	Mahesh Salgaonkar <mahesh@linux.ibm.com>
Subject: [PATCH 4/8] KVM: PPC: Book3S HV: Ratelimit machine check messages coming from guests
Date: Sat, 28 Nov 2020 17:07:24 +1000	[thread overview]
Message-ID: <20201128070728.825934-5-npiggin@gmail.com> (raw)
In-Reply-To: <20201128070728.825934-1-npiggin@gmail.com>

A number of machine check exceptions are triggerable by the guest.
Ratelimit these to avoid a guest flooding the host console and logs.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/kvm/book3s_hv.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index e3b1839fc251..c94f9595133d 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -1328,8 +1328,12 @@ static int kvmppc_handle_exit_hv(struct kvm_vcpu *vcpu,
 		r = RESUME_GUEST;
 		break;
 	case BOOK3S_INTERRUPT_MACHINE_CHECK:
-		/* Print the MCE event to host console. */
-		machine_check_print_event_info(&vcpu->arch.mce_evt, false, true);
+		/*
+		 * Print the MCE event to host console. Ratelimit so the guest
+		 * can't flood the host log.
+		 */
+		if (printk_ratelimit())
+			machine_check_print_event_info(&vcpu->arch.mce_evt,false, true);
 
 		/*
 		 * If the guest can do FWNMI, exit to userspace so it can
@@ -1519,7 +1523,8 @@ static int kvmppc_handle_nested_exit(struct kvm_vcpu *vcpu)
 		/* Pass the machine check to the L1 guest */
 		r = RESUME_HOST;
 		/* Print the MCE event to host console. */
-		machine_check_print_event_info(&vcpu->arch.mce_evt, false, true);
+		if (printk_ratelimit())
+			machine_check_print_event_info(&vcpu->arch.mce_evt, false, true);
 		break;
 	/*
 	 * We get these next two if the guest accesses a page which it thinks
-- 
2.23.0

