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x86/reboot: Assert that IRQs are disabled when turning off virtualization

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Assert that IRQs are disabled when turning off virtualization in an
emergency.  KVM enables hardware via on_each_cpu(), i.e. could re-enable
hardware if a pending IPI were delivered after disabling virtualization.

Remove a misleading comment from emergency_reboot_disable_virtualization()
about "just" needing to guarantee the CPU is stable (see above).

Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20230721201859.2307736-6-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2023-07-21 13:18:45 -07:00
parent baeb4de7ad
commit ad93c1a7c0
1 changed files with 7 additions and 1 deletions
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8
arch/x86/kernel/reboot.c
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@ -532,7 +532,6 @@ static inline void nmi_shootdown_cpus_on_restart(void);
static void emergency_reboot_disable_virtualization(void)
{
/* Just make sure we won't change CPUs while doing this */
local_irq_disable();
/*
@ -821,6 +820,13 @@ void cpu_emergency_disable_virtualization(void)
{
cpu_emergency_virt_cb *callback;
/*
* IRQs must be disabled as KVM enables virtualization in hardware via
* function call IPIs, i.e. IRQs need to be disabled to guarantee
* virtualization stays disabled.
*/
lockdep_assert_irqs_disabled();
rcu_read_lock();
callback = rcu_dereference(cpu_emergency_virt_callback);
if (callback)