linux-kernel - [PATCH 06/14] KVM: arm64: Return next table from map callbacks

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Date:   Tue, 30 Aug 2022 19:41:24 +0000
From:   Oliver Upton <oliver.upton@...ux.dev>
To:     Marc Zyngier <maz@...nel.org>, James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Quentin Perret <qperret@...gle.com>,
        Ricardo Koller <ricarkol@...gle.com>,
        Reiji Watanabe <reijiw@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Ben Gardon <bgardon@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Gavin Shan <gshan@...hat.com>, Peter Xu <peterx@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Oliver Upton <oliver.upton@...ux.dev>
Cc:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 06/14] KVM: arm64: Return next table from map callbacks

The map walkers install new page tables during their traversal. Return
the newly-installed table PTE from the map callbacks to point the walker
at the new table w/o rereading the ptep.

Signed-off-by: Oliver Upton <oliver.upton@...ux.dev>
---
 arch/arm64/kvm/hyp/pgtable.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 331f6e3b2c20..f911509e6512 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -202,13 +202,12 @@ static inline int __kvm_pgtable_visit(struct kvm_pgtable_walk_data *data,
 	if (!table && (flags & KVM_PGTABLE_WALK_LEAF)) {
 		ret = kvm_pgtable_visitor_cb(data, addr, level, ptep, &pte,
 					     KVM_PGTABLE_WALK_LEAF);
-		pte = *ptep;
-		table = kvm_pte_table(pte, level);
 	}
 
 	if (ret)
 		goto out;
 
+	table = kvm_pte_table(pte, level);
 	if (!table) {
 		data->addr = ALIGN_DOWN(data->addr, kvm_granule_size(level));
 		data->addr += kvm_granule_size(level);
@@ -427,6 +426,7 @@ static int hyp_map_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep, kvm_pte
 	new = kvm_init_table_pte(childp, mm_ops);
 	mm_ops->get_page(ptep);
 	smp_store_release(ptep, new);
+	*old = new;
 
 	return 0;
 }
@@ -768,7 +768,7 @@ static int stage2_map_walker_try_leaf(u64 addr, u64 end, u32 level,
 }
 
 static int stage2_map_walk_leaf(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
-				struct stage2_map_data *data);
+				kvm_pte_t *old, struct stage2_map_data *data);
 
 static int stage2_map_walk_table_pre(u64 addr, u64 end, u32 level,
 				     kvm_pte_t *ptep, kvm_pte_t *old,
@@ -791,7 +791,7 @@ static int stage2_map_walk_table_pre(u64 addr, u64 end, u32 level,
 	 */
 	kvm_call_hyp(__kvm_tlb_flush_vmid, data->mmu);
 
-	ret = stage2_map_walk_leaf(addr, end, level, ptep, data);
+	ret = stage2_map_walk_leaf(addr, end, level, ptep, old, data);
 
 	mm_ops->put_page(ptep);
 	mm_ops->free_removed_table(childp, level + 1, pgt);
@@ -832,6 +832,7 @@ static int stage2_map_walk_leaf(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
 	new = kvm_init_table_pte(childp, mm_ops);
 	mm_ops->get_page(ptep);
 	smp_store_release(ptep, new);
+	*old = new;
 
 	return 0;
 }
-- 
2.37.2.672.g94769d06f0-goog