linux-kernel - [RFC PATCH 23/26] x86/kvm: Add worker to trigger runtime patching

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Date:   Tue,  7 Apr 2020 22:03:20 -0700
From:   Ankur Arora <ankur.a.arora@...cle.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     peterz@...radead.org, hpa@...or.com, jpoimboe@...hat.com,
        namit@...are.com, mhiramat@...nel.org, jgross@...e.com,
        bp@...en8.de, vkuznets@...hat.com, pbonzini@...hat.com,
        boris.ostrovsky@...cle.com, mihai.carabas@...cle.com,
        kvm@...r.kernel.org, xen-devel@...ts.xenproject.org,
        virtualization@...ts.linux-foundation.org,
        Ankur Arora <ankur.a.arora@...cle.com>
Subject: [RFC PATCH 23/26] x86/kvm: Add worker to trigger runtime patching

Make __pv_init_lock_hash() conditional on either paravirt spinlocks
being enabled (via kvm_pv_spinlock()) or if paravirt spinlocks
might get enabled (runtime patching via CONFIG_PARAVIRT_RUNTIME.)

Also add a handler for CPUID reprobe which can trigger this patching.

Signed-off-by: Ankur Arora <ankur.a.arora@...cle.com>
---
 arch/x86/kernel/kvm.c | 34 +++++++++++++++++++++++++++++-----
 1 file changed, 29 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 31f5ecfd3907..1cb7eab805a6 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -35,6 +35,7 @@
 #include <asm/hypervisor.h>
 #include <asm/tlb.h>
 #include <asm/cpuidle_haltpoll.h>
+#include <asm/text-patching.h>
 
 static int kvmapf = 1;
 
@@ -909,12 +910,15 @@ void __init kvm_spinlock_init(void)
 	if (num_possible_cpus() == 1)
 		return;
 
-	if (!kvm_pv_spinlock())
-		return;
-
-	__pv_init_lock_hash();
+	/*
+	 * Allocate if pv_spinlocks are enabled or if we might
+	 * end up patching them in later.
+	 */
+	if (kvm_pv_spinlock() || IS_ENABLED(CONFIG_PARAVIRT_RUNTIME))
+		__pv_init_lock_hash();
 }
-
+#else	/* !CONFIG_PARAVIRT_SPINLOCKS */
+static inline bool kvm_pv_spinlock(void) { return false; }
 #endif	/* CONFIG_PARAVIRT_SPINLOCKS */
 
 #ifdef CONFIG_ARCH_CPUIDLE_HALTPOLL
@@ -952,3 +956,23 @@ void arch_haltpoll_disable(unsigned int cpu)
 }
 EXPORT_SYMBOL_GPL(arch_haltpoll_disable);
 #endif
+
+#ifdef CONFIG_PARAVIRT_RUNTIME
+void kvm_trigger_reprobe_cpuid(struct work_struct *work)
+{
+	mutex_lock(&text_mutex);
+
+	paravirt_stage_zero();
+
+	kvm_pv_steal_clock();
+	kvm_pv_tlb();
+	paravirt_runtime_patch(false);
+
+	paravirt_stage_zero();
+
+	kvm_pv_spinlock();
+	paravirt_runtime_patch(true);
+
+	mutex_unlock(&text_mutex);
+}
+#endif /* CONFIG_PARAVIRT_RUNTIME */
-- 
2.20.1