linux-kernel - [PATCH v6 33/38] KVM: arm64: Introduce KVM_PGTABLE_S2

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Message-Id: <20210319100146.1149909-34-qperret@google.com>
Date:   Fri, 19 Mar 2021 10:01:41 +0000
From:   Quentin Perret <qperret@...gle.com>
To:     catalin.marinas@....com, will@...nel.org, maz@...nel.org,
        james.morse@....com, julien.thierry.kdev@...il.com,
        suzuki.poulose@....com
Cc:     android-kvm@...gle.com, seanjc@...gle.com, mate.toth-pal@....com,
        linux-kernel@...r.kernel.org, robh+dt@...nel.org,
        linux-arm-kernel@...ts.infradead.org, kernel-team@...roid.com,
        kvmarm@...ts.cs.columbia.edu, tabba@...gle.com, ardb@...nel.org,
        mark.rutland@....com, dbrazdil@...gle.com, qperret@...gle.com
Subject: [PATCH v6 33/38] KVM: arm64: Introduce KVM_PGTABLE_S2_IDMAP stage 2 flag

Introduce a new stage 2 configuration flag to specify that all mappings
in a given page-table will be identity-mapped, as will be the case for
the host. This allows to introduce sanity checks in the map path and to
avoid programming errors.

Suggested-by: Will Deacon <will@...nel.org>
Signed-off-by: Quentin Perret <qperret@...gle.com>
---
 arch/arm64/include/asm/kvm_pgtable.h | 2 ++
 arch/arm64/kvm/hyp/pgtable.c         | 3 +++
 2 files changed, 5 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index 55452f4831d2..c3674c47d48c 100644
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -60,9 +60,11 @@ struct kvm_pgtable_mm_ops {
  * enum kvm_pgtable_stage2_flags - Stage-2 page-table flags.
  * @KVM_PGTABLE_S2_NOFWB:	Don't enforce Normal-WB even if the CPUs have
  *				ARM64_HAS_STAGE2_FWB.
+ * @KVM_PGTABLE_S2_IDMAP:	Only use identity mappings.
  */
 enum kvm_pgtable_stage2_flags {
 	KVM_PGTABLE_S2_NOFWB			= BIT(0),
+	KVM_PGTABLE_S2_IDMAP			= BIT(1),
 };
 
 /**
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index b22b4860630c..c37c1dc4feaf 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -760,6 +760,9 @@ int kvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 addr, u64 size,
 		.arg		= &map_data,
 	};
 
+	if (WARN_ON((pgt->flags & KVM_PGTABLE_S2_IDMAP) && (addr != phys)))
+		return -EINVAL;
+
 	ret = stage2_set_prot_attr(pgt, prot, &map_data.attr);
 	if (ret)
 		return ret;
-- 
2.31.0.rc2.261.g7f71774620-goog