Commit b0d23708 authored by Jun Miao's avatar Jun Miao Committed by Sean Christopherson
Browse files

KVM: Fix comments that refer to the non-existent install_new_memslots() 



Fix stale comments that were left behind when install_new_memslots() was
replaced by kvm_swap_active_memslots() as part of the scalable memslots
rework.

Fixes: a54d8066 ("KVM: Keep memslots in tree-based structures instead of array-based ones")
Signed-off-by: default avatarJun Miao <jun.miao@intel.com>
Link: https://lore.kernel.org/r/20230223052851.1054799-1-jun.miao@intel.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 7ffc2e89

Documentation/virt/kvm/locking.rst

+1 −1
Original line number Diff line number Diff line
@@ -21,7 +21,7 @@ The acquisition orders for mutexes are as follows: 
- kvm->mn_active_invalidate_count ensures that pairs of

  invalidate_range_start() and invalidate_range_end() callbacks

  use the same memslots array.  kvm->slots_lock and kvm->slots_arch_lock

  are taken on the waiting side in install_new_memslots, so MMU notifiers

  are taken on the waiting side when modifying memslots, so MMU notifiers

  must not take either kvm->slots_lock or kvm->slots_arch_lock.



For SRCU:

include/linux/kvm_host.h

+2 −2
Original line number Diff line number Diff line
@@ -58,7 +58,7 @@ 


/*

 * Bit 63 of the memslot generation number is an "update in-progress flag",

 * e.g. is temporarily set for the duration of install_new_memslots().

 * e.g. is temporarily set for the duration of kvm_swap_active_memslots().

 * This flag effectively creates a unique generation number that is used to

 * mark cached memslot data, e.g. MMIO accesses, as potentially being stale,

 * i.e. may (or may not) have come from the previous memslots generation.
@@ -713,7 +713,7 @@ struct kvm { 
	 * use by the VM. To be used under the slots_lock (above) or in a

	 * kvm->srcu critical section where acquiring the slots_lock would

	 * lead to deadlock with the synchronize_srcu in

	 * install_new_memslots.

	 * kvm_swap_active_memslots().

	 */

	struct mutex slots_arch_lock;

	struct mm_struct *mm; /* userspace tied to this vm */

virt/kvm/kvm_main.c

+7 −7
Original line number Diff line number Diff line
@@ -1298,7 +1298,7 @@ static void kvm_destroy_vm(struct kvm *kvm) 
	 * At this point, pending calls to invalidate_range_start()

	 * have completed but no more MMU notifiers will run, so

	 * mn_active_invalidate_count may remain unbalanced.

	 * No threads can be waiting in install_new_memslots as the

	 * No threads can be waiting in kvm_swap_active_memslots() as the

	 * last reference on KVM has been dropped, but freeing

	 * memslots would deadlock without this manual intervention.

	 */
@@ -1742,13 +1742,13 @@ static void kvm_invalidate_memslot(struct kvm *kvm, 
	kvm_arch_flush_shadow_memslot(kvm, old);

	kvm_arch_guest_memory_reclaimed(kvm);



	/* Was released by kvm_swap_active_memslots, reacquire. */

	/* Was released by kvm_swap_active_memslots(), reacquire. */

	mutex_lock(&kvm->slots_arch_lock);



	/*

	 * Copy the arch-specific field of the newly-installed slot back to the

	 * old slot as the arch data could have changed between releasing

	 * slots_arch_lock in install_new_memslots() and re-acquiring the lock

	 * slots_arch_lock in kvm_swap_active_memslots() and re-acquiring the lock

	 * above.  Writers are required to retrieve memslots *after* acquiring

	 * slots_arch_lock, thus the active slot's data is guaranteed to be fresh.

	 */
@@ -1810,11 +1810,11 @@ static int kvm_set_memslot(struct kvm *kvm, 
	int r;



	/*

	 * Released in kvm_swap_active_memslots.

	 * Released in kvm_swap_active_memslots().

	 *

	 * Must be held from before the current memslots are copied until

	 * after the new memslots are installed with rcu_assign_pointer,

	 * then released before the synchronize srcu in kvm_swap_active_memslots.

	 * Must be held from before the current memslots are copied until after

	 * the new memslots are installed with rcu_assign_pointer, then

	 * released before the synchronize srcu in kvm_swap_active_memslots().

	 *

	 * When modifying memslots outside of the slots_lock, must be held

	 * before reading the pointer to the current memslots until after all