Commit 8e94e125 authored by Oliver Upton's avatar Oliver Upton Committed by Marc Zyngier
Browse files

KVM: arm64: Add a helper to tear down unlinked stage-2 subtrees 



A subsequent change to KVM will move the tear down of an unlinked
stage-2 subtree out of the critical path of the break-before-make
sequence.

Introduce a new helper for tearing down unlinked stage-2 subtrees.
Leverage the existing stage-2 free walkers to do so, with a deep call
into __kvm_pgtable_walk() as the subtree is no longer reachable from the
root.

Signed-off-by: default avatarOliver Upton <oliver.upton@linux.dev>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221107215644.1895162-6-oliver.upton@linux.dev
parent fa002e8e

arch/arm64/include/asm/kvm_pgtable.h

+11 −0
Original line number Diff line number Diff line
@@ -333,6 +333,17 @@ int __kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm_s2_mmu *mmu, 
 */

void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt);



/**

 * kvm_pgtable_stage2_free_removed() - Free a removed stage-2 paging structure.

 * @mm_ops:	Memory management callbacks.

 * @pgtable:	Unlinked stage-2 paging structure to be freed.

 * @level:	Level of the stage-2 paging structure to be freed.

 *

 * The page-table is assumed to be unreachable by any hardware walkers prior to

 * freeing and therefore no TLB invalidation is performed.

 */

void kvm_pgtable_stage2_free_removed(struct kvm_pgtable_mm_ops *mm_ops, void *pgtable, u32 level);



/**

 * kvm_pgtable_stage2_map() - Install a mapping in a guest stage-2 page-table.

 * @pgt:	Page-table structure initialised by kvm_pgtable_stage2_init*().

arch/arm64/kvm/hyp/pgtable.c

+23 −0
Original line number Diff line number Diff line
@@ -1203,3 +1203,26 @@ void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt) 
	pgt->mm_ops->free_pages_exact(pgt->pgd, pgd_sz);

	pgt->pgd = NULL;

}



void kvm_pgtable_stage2_free_removed(struct kvm_pgtable_mm_ops *mm_ops, void *pgtable, u32 level)

{

	kvm_pte_t *ptep = (kvm_pte_t *)pgtable;

	struct kvm_pgtable_walker walker = {

		.cb	= stage2_free_walker,

		.flags	= KVM_PGTABLE_WALK_LEAF |

			  KVM_PGTABLE_WALK_TABLE_POST,

	};

	struct kvm_pgtable_walk_data data = {

		.walker	= &walker,



		/*

		 * At this point the IPA really doesn't matter, as the page

		 * table being traversed has already been removed from the stage

		 * 2. Set an appropriate range to cover the entire page table.

		 */

		.addr	= 0,

		.end	= kvm_granule_size(level),

	};



	WARN_ON(__kvm_pgtable_walk(&data, mm_ops, ptep, level));

}