From 2f7c68cb55ecb7331f2381deb497c27155f32faf Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Wed, 03 Jan 2024 09:43:39 +0000
Subject: [PATCH] update kernel to 5.10.198
---
kernel/arch/x86/kernel/reboot.c | 88 ++++++++++++++++++++++++++++++++------------
1 files changed, 64 insertions(+), 24 deletions(-)
diff --git a/kernel/arch/x86/kernel/reboot.c b/kernel/arch/x86/kernel/reboot.c
index df35148..4d8c0e2 100644
--- a/kernel/arch/x86/kernel/reboot.c
+++ b/kernel/arch/x86/kernel/reboot.c
@@ -528,33 +528,29 @@
}
}
-static void vmxoff_nmi(int cpu, struct pt_regs *regs)
-{
- cpu_emergency_vmxoff();
-}
+static inline void nmi_shootdown_cpus_on_restart(void);
-/* Use NMIs as IPIs to tell all CPUs to disable virtualization */
-static void emergency_vmx_disable_all(void)
+static void emergency_reboot_disable_virtualization(void)
{
/* Just make sure we won't change CPUs while doing this */
local_irq_disable();
/*
- * Disable VMX on all CPUs before rebooting, otherwise we risk hanging
- * the machine, because the CPU blocks INIT when it's in VMX root.
+ * Disable virtualization on all CPUs before rebooting to avoid hanging
+ * the system, as VMX and SVM block INIT when running in the host.
*
* We can't take any locks and we may be on an inconsistent state, so
- * use NMIs as IPIs to tell the other CPUs to exit VMX root and halt.
+ * use NMIs as IPIs to tell the other CPUs to disable VMX/SVM and halt.
*
- * Do the NMI shootdown even if VMX if off on _this_ CPU, as that
- * doesn't prevent a different CPU from being in VMX root operation.
+ * Do the NMI shootdown even if virtualization is off on _this_ CPU, as
+ * other CPUs may have virtualization enabled.
*/
- if (cpu_has_vmx()) {
- /* Safely force _this_ CPU out of VMX root operation. */
- __cpu_emergency_vmxoff();
+ if (cpu_has_vmx() || cpu_has_svm(NULL)) {
+ /* Safely force _this_ CPU out of VMX/SVM operation. */
+ cpu_emergency_disable_virtualization();
- /* Halt and exit VMX root operation on the other CPUs. */
- nmi_shootdown_cpus(vmxoff_nmi);
+ /* Disable VMX/SVM and halt on other CPUs. */
+ nmi_shootdown_cpus_on_restart();
}
}
@@ -590,7 +586,7 @@
unsigned short mode;
if (reboot_emergency)
- emergency_vmx_disable_all();
+ emergency_reboot_disable_virtualization();
tboot_shutdown(TB_SHUTDOWN_REBOOT);
@@ -795,6 +791,17 @@
/* This is the CPU performing the emergency shutdown work. */
int crashing_cpu = -1;
+/*
+ * Disable virtualization, i.e. VMX or SVM, to ensure INIT is recognized during
+ * reboot. VMX blocks INIT if the CPU is post-VMXON, and SVM blocks INIT if
+ * GIF=0, i.e. if the crash occurred between CLGI and STGI.
+ */
+void cpu_emergency_disable_virtualization(void)
+{
+ cpu_emergency_vmxoff();
+ cpu_emergency_svm_disable();
+}
+
#if defined(CONFIG_SMP)
static nmi_shootdown_cb shootdown_callback;
@@ -817,7 +824,14 @@
return NMI_HANDLED;
local_irq_disable();
- shootdown_callback(cpu, regs);
+ if (shootdown_callback)
+ shootdown_callback(cpu, regs);
+
+ /*
+ * Prepare the CPU for reboot _after_ invoking the callback so that the
+ * callback can safely use virtualization instructions, e.g. VMCLEAR.
+ */
+ cpu_emergency_disable_virtualization();
atomic_dec(&waiting_for_crash_ipi);
/* Assume hlt works */
@@ -828,17 +842,31 @@
return NMI_HANDLED;
}
-/*
- * Halt all other CPUs, calling the specified function on each of them
+/**
+ * nmi_shootdown_cpus - Stop other CPUs via NMI
+ * @callback: Optional callback to be invoked from the NMI handler
*
- * This function can be used to halt all other CPUs on crash
- * or emergency reboot time. The function passed as parameter
- * will be called inside a NMI handler on all CPUs.
+ * The NMI handler on the remote CPUs invokes @callback, if not
+ * NULL, first and then disables virtualization to ensure that
+ * INIT is recognized during reboot.
+ *
+ * nmi_shootdown_cpus() can only be invoked once. After the first
+ * invocation all other CPUs are stuck in crash_nmi_callback() and
+ * cannot respond to a second NMI.
*/
void nmi_shootdown_cpus(nmi_shootdown_cb callback)
{
unsigned long msecs;
+
local_irq_disable();
+
+ /*
+ * Avoid certain doom if a shootdown already occurred; re-registering
+ * the NMI handler will cause list corruption, modifying the callback
+ * will do who knows what, etc...
+ */
+ if (WARN_ON_ONCE(crash_ipi_issued))
+ return;
/* Make a note of crashing cpu. Will be used in NMI callback. */
crashing_cpu = safe_smp_processor_id();
@@ -867,7 +895,17 @@
msecs--;
}
- /* Leave the nmi callback set */
+ /*
+ * Leave the nmi callback set, shootdown is a one-time thing. Clearing
+ * the callback could result in a NULL pointer dereference if a CPU
+ * (finally) responds after the timeout expires.
+ */
+}
+
+static inline void nmi_shootdown_cpus_on_restart(void)
+{
+ if (!crash_ipi_issued)
+ nmi_shootdown_cpus(NULL);
}
/*
@@ -897,6 +935,8 @@
/* No other CPUs to shoot down */
}
+static inline void nmi_shootdown_cpus_on_restart(void) { }
+
void run_crash_ipi_callback(struct pt_regs *regs)
{
}
--
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