linux-kernel - [PATCH v7 01/45] KVM: Prepare for handling only shared mappings in mmu

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Message-ID: <20250213161426.102987-2-steven.price@arm.com>
Date: Thu, 13 Feb 2025 16:13:41 +0000
From: Steven Price <steven.price@....com>
To: kvm@...r.kernel.org,
	kvmarm@...ts.linux.dev
Cc: Sean Christopherson <seanjc@...gle.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Marc Zyngier <maz@...nel.org>,
	Will Deacon <will@...nel.org>,
	James Morse <james.morse@....com>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Joey Gouly <joey.gouly@....com>,
	Alexandru Elisei <alexandru.elisei@....com>,
	Christoffer Dall <christoffer.dall@....com>,
	Fuad Tabba <tabba@...gle.com>,
	linux-coco@...ts.linux.dev,
	Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>,
	Gavin Shan <gshan@...hat.com>,
	Shanker Donthineni <sdonthineni@...dia.com>,
	Alper Gun <alpergun@...gle.com>,
	"Aneesh Kumar K . V" <aneesh.kumar@...nel.org>,
	Steven Price <steven.price@....com>
Subject: [PATCH v7 01/45] KVM: Prepare for handling only shared mappings in mmu_notifier events

From: Sean Christopherson <seanjc@...gle.com>

Add flags to "struct kvm_gfn_range" to let notifier events target only
shared and only private mappings, and write up the existing mmu_notifier
events to be shared-only (private memory is never associated with a
userspace virtual address, i.e. can't be reached via mmu_notifiers).

Add two flags so that KVM can handle the three possibilities (shared,
private, and shared+private) without needing something like a tri-state
enum.

Link: https://lore.kernel.org/all/ZJX0hk+KpQP0KUyB@google.com
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Steven Price <steven.price@....com>
---
 include/linux/kvm_host.h | 2 ++
 virt/kvm/kvm_main.c      | 7 +++++++
 2 files changed, 9 insertions(+)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 3cb9a32a6330..0de1e485452c 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -266,6 +266,8 @@ struct kvm_gfn_range {
 	gfn_t end;
 	union kvm_mmu_notifier_arg arg;
 	enum kvm_gfn_range_filter attr_filter;
+	bool only_private;
+	bool only_shared;
 	bool may_block;
 };
 bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index faf10671eed2..4f0136094fac 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -593,6 +593,13 @@ static __always_inline kvm_mn_ret_t __kvm_handle_hva_range(struct kvm *kvm,
 			 * the second or later invocation of the handler).
 			 */
 			gfn_range.arg = range->arg;
+
+			/*
+			 * HVA-based notifications aren't relevant to private
+			 * mappings as they don't have a userspace mapping.
+			 */
+			gfn_range.only_private = false;
+			gfn_range.only_shared = true;
 			gfn_range.may_block = range->may_block;
 			/*
 			 * HVA-based notifications aren't relevant to private
-- 
2.43.0