linux-kernel - [PATCH 13/14] KVM: arm64: Make table->block changes parallel-aware

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Date:   Tue, 30 Aug 2022 19:51:51 +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>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        kvm@...r.kernel.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>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 13/14] KVM: arm64: Make table->block changes parallel-aware

stage2_map_walk_leaf() and friends now handle stage-2 PTEs generically,
and perform the correct flush when a table PTE is removed. Additionally,
they've been made parallel-aware, using an atomic break to take
ownership of the PTE.

Stop clearing the PTE in the pre-order callback and instead let
stage2_map_walk_leaf() deal with it.

Signed-off-by: Oliver Upton <oliver.upton@...ux.dev>
---
 arch/arm64/kvm/hyp/pgtable.c | 15 +++------------
 1 file changed, 3 insertions(+), 12 deletions(-)

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index de1d352657d0..92e230e7bf3a 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -871,21 +871,12 @@ static int stage2_map_walk_table_pre(u64 addr, u64 end, u32 level,
 	if (!stage2_leaf_mapping_allowed(addr, end, level, data))
 		return 0;
 
-	kvm_clear_pte(ptep);
-
-	/*
-	 * Invalidate the whole stage-2, as we may have numerous leaf
-	 * entries below us which would otherwise need invalidating
-	 * individually.
-	 */
-	kvm_call_hyp(__kvm_tlb_flush_vmid, data->mmu);
-
 	ret = stage2_map_walk_leaf(addr, end, level, ptep, old, data);
+	if (ret)
+		return ret;
 
-	mm_ops->put_page(ptep);
 	mm_ops->free_removed_table(childp, level + 1, pgt);
-
-	return ret;
+	return 0;
 }
 
 static int stage2_map_walk_leaf(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
-- 
2.37.2.672.g94769d06f0-goog