[PATCH] KVM: Fix obsolete comment about locking for kvm_io_bus_read/write

[PATCH] KVM: Fix obsolete comment about locking for kvm_io_bus_read/write

[Li RongQing]

Nobody is actually calling these functions with slots_lock held.
The srcu read lock is required.

Signed-off-by: Li RongQing <lirongqing@baidu.com>
---
 virt/kvm/kvm_main.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e85b33a..2e591cc 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -5774,7 +5774,7 @@ static int __kvm_io_bus_write(struct kvm_vcpu *vcpu, struct kvm_io_bus *bus,
 	return -EOPNOTSUPP;
 }
 
-/* kvm_io_bus_write - called under kvm->slots_lock */
+/* kvm_io_bus_write - called under kvm->srcu read lock */
 int kvm_io_bus_write(struct kvm_vcpu *vcpu, enum kvm_bus bus_idx, gpa_t addr,
 		     int len, const void *val)
 {
@@ -5795,7 +5795,7 @@ int kvm_io_bus_write(struct kvm_vcpu *vcpu, enum kvm_bus bus_idx, gpa_t addr,
 }
 EXPORT_SYMBOL_GPL(kvm_io_bus_write);
 
-/* kvm_io_bus_write_cookie - called under kvm->slots_lock */
+/* kvm_io_bus_write_cookie - called under kvm->srcu read lock */
 int kvm_io_bus_write_cookie(struct kvm_vcpu *vcpu, enum kvm_bus bus_idx,
 			    gpa_t addr, int len, const void *val, long cookie)
 {
@@ -5845,7 +5845,7 @@ static int __kvm_io_bus_read(struct kvm_vcpu *vcpu, struct kvm_io_bus *bus,
 	return -EOPNOTSUPP;
 }
 
-/* kvm_io_bus_read - called under kvm->slots_lock */
+/* kvm_io_bus_read - called under kvm->srcu read lock */
 int kvm_io_bus_read(struct kvm_vcpu *vcpu, enum kvm_bus bus_idx, gpa_t addr,
 		    int len, void *val)
 {
-- 
2.9.4

Re: [PATCH] KVM: Fix obsolete comment about locking for kvm_io_bus_read/write

[Sean Christopherson]

On Fri, Apr 18, 2025, Li RongQing wrote:
> Nobody is actually calling these functions with slots_lock held.
> The srcu read lock is required.

I vote to delete the comments entirely, the srcu_dereference() precisely communicates
both what is being protected, and what provides the protection.

答复: [????] Re: [PATCH] KVM: Fix obsolete comment about locking for kvm_io_bus_read/write

[Li,Rongqing]

> 
> On Fri, Apr 18, 2025, Li RongQing wrote:
> > Nobody is actually calling these functions with slots_lock held.
> > The srcu read lock is required.
> 
> I vote to delete the comments entirely, the srcu_dereference() precisely
> communicates both what is being protected, and what provides the protection.


Ok, I will resend this patch

Thank

-Li