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KVM: x86: Don't disable IRQs when unregistering user-return notifier

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Remove the code to disable IRQs when unregistering KVM's user-return
notifier now that KVM doesn't invoke kvm_on_user_return() when disabling
virtualization via IPI function call, i.e. now that there's no need to
guard against re-entrancy via IPI callback.

Note, disabling IRQs has largely been unnecessary since commit
a377ac1cd9d7b ("x86/entry: Move user return notifier out of loop") moved
fire_user_return_notifiers() into the section with IRQs disabled.  In doing
so, the commit somewhat inadvertently fixed the underlying issue that
was papered over by commit 1650b4ebc99d ("KVM: Disable irq while
unregistering user notifier").  I.e. in practice, the code and comment
has been stale since commit a377ac1cd9d7b.

Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
[sean: rewrite changelog after rebasing, drop lockdep assert]
Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://patch.msgid.link/20251030191528.3380553-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Hou Wenlong 2025-10-30 12:15:28 -07:00 committed by Sean Christopherson
parent 2baa33a8dd
commit 995d504100
1 changed files with 3 additions and 11 deletions
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14
arch/x86/kvm/x86.c
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@ -602,18 +602,10 @@ static void kvm_on_user_return(struct user_return_notifier *urn)
struct kvm_user_return_msrs *msrs
= container_of(urn, struct kvm_user_return_msrs, urn);
struct kvm_user_return_msr_values *values;
unsigned long flags;
/*
* Disabling irqs at this point since the following code could be
* interrupted and executed through kvm_arch_disable_virtualization_cpu()
*/
local_irq_save(flags);
if (msrs->registered) {
msrs->registered = false;
user_return_notifier_unregister(urn);
}
local_irq_restore(flags);
msrs->registered = false;
user_return_notifier_unregister(urn);
for (slot = 0; slot < kvm_nr_uret_msrs; ++slot) {
values = &msrs->values[slot];
if (values->host != values->curr) {