linux-kernel - [PATCH v8 -tip 15/26] entry/kvm: Protect the kernel when entering from guest

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Date:   Mon, 19 Oct 2020 21:43:25 -0400
From:   "Joel Fernandes (Google)" <joel@...lfernandes.org>
To:     Nishanth Aravamudan <naravamudan@...italocean.com>,
        Julien Desfossez <jdesfossez@...italocean.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Vineeth Pillai <viremana@...ux.microsoft.com>,
        Aaron Lu <aaron.lwe@...il.com>,
        Aubrey Li <aubrey.intel@...il.com>, tglx@...utronix.de,
        linux-kernel@...r.kernel.org
Cc:     mingo@...nel.org, torvalds@...ux-foundation.org,
        fweisbec@...il.com, keescook@...omium.org, kerrnel@...gle.com,
        Phil Auld <pauld@...hat.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>, joel@...lfernandes.org,
        vineeth@...byteword.org, Chen Yu <yu.c.chen@...el.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Agata Gruza <agata.gruza@...el.com>,
        Antonio Gomez Iglesias <antonio.gomez.iglesias@...el.com>,
        graf@...zon.com, konrad.wilk@...cle.com, dfaggioli@...e.com,
        pjt@...gle.com, rostedt@...dmis.org, derkling@...gle.com,
        benbjiang@...cent.com,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        James.Bottomley@...senpartnership.com, OWeisse@...ch.edu,
        Dhaval Giani <dhaval.giani@...cle.com>,
        Junaid Shahid <junaids@...gle.com>, jsbarnes@...gle.com,
        chris.hyser@...cle.com, Aubrey Li <aubrey.li@...ux.intel.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Tim Chen <tim.c.chen@...el.com>
Subject: [PATCH v8 -tip 15/26] entry/kvm: Protect the kernel when entering from guest

From: Vineeth Pillai <viremana@...ux.microsoft.com>

Similar to how user to kernel mode transitions are protected in earlier
patches, protect the entry into kernel from guest mode as well.

Tested-by: Julien Desfossez <jdesfossez@...italocean.com>
Signed-off-by: Vineeth Pillai <viremana@...ux.microsoft.com>
---
 arch/x86/kvm/x86.c        |  3 +++
 include/linux/entry-kvm.h | 12 ++++++++++++
 kernel/entry/kvm.c        | 13 +++++++++++++
 3 files changed, 28 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ce856e0ece84..05a281f3ef28 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8540,6 +8540,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 	 */
 	smp_mb__after_srcu_read_unlock();
 
+	kvm_exit_to_guest_mode(vcpu);
+
 	/*
 	 * This handles the case where a posted interrupt was
 	 * notified with kvm_vcpu_kick.
@@ -8633,6 +8635,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 		}
 	}
 
+	kvm_enter_from_guest_mode(vcpu);
 	local_irq_enable();
 	preempt_enable();
 
diff --git a/include/linux/entry-kvm.h b/include/linux/entry-kvm.h
index 0cef17afb41a..32aabb7f3e6d 100644
--- a/include/linux/entry-kvm.h
+++ b/include/linux/entry-kvm.h
@@ -77,4 +77,16 @@ static inline bool xfer_to_guest_mode_work_pending(void)
 }
 #endif /* CONFIG_KVM_XFER_TO_GUEST_WORK */
 
+/**
+ * kvm_enter_from_guest_mode - Hook called just after entering kernel from guest.
+ * @vcpu:   Pointer to the current VCPU data
+ */
+void kvm_enter_from_guest_mode(struct kvm_vcpu *vcpu);
+
+/**
+ * kvm_exit_to_guest_mode - Hook called just before entering guest from kernel.
+ * @vcpu:   Pointer to the current VCPU data
+ */
+void kvm_exit_to_guest_mode(struct kvm_vcpu *vcpu);
+
 #endif
diff --git a/kernel/entry/kvm.c b/kernel/entry/kvm.c
index eb1a8a4c867c..b0b7facf4374 100644
--- a/kernel/entry/kvm.c
+++ b/kernel/entry/kvm.c
@@ -49,3 +49,16 @@ int xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu)
 	return xfer_to_guest_mode_work(vcpu, ti_work);
 }
 EXPORT_SYMBOL_GPL(xfer_to_guest_mode_handle_work);
+
+void kvm_enter_from_guest_mode(struct kvm_vcpu *vcpu)
+{
+	sched_core_unsafe_enter();
+}
+EXPORT_SYMBOL_GPL(kvm_enter_from_guest_mode);
+
+void kvm_exit_to_guest_mode(struct kvm_vcpu *vcpu)
+{
+	sched_core_unsafe_exit();
+	sched_core_wait_till_safe(XFER_TO_GUEST_MODE_WORK);
+}
+EXPORT_SYMBOL_GPL(kvm_exit_to_guest_mode);
-- 
2.29.0.rc1.297.gfa9743e501-goog