linux-kernel - [PATCH v4 3/5] kvm: arm64: New memslot flag to indicate cacheable mapping

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Message-ID: <20250518054754.5345-4-ankita@nvidia.com>
Date: Sun, 18 May 2025 05:47:52 +0000
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Subject: [PATCH v4 3/5] kvm: arm64: New memslot flag to indicate cacheable mapping

From: Ankit Agrawal <ankita@...dia.com>

Introduce a new memslot flag KVM_MEM_ENABLE_CACHEABLE_PFNMAP
as a tool for userspace to indicate that it expects a particular
PFN range to be mapped cacheable.

This will serve as a guide for the KVM to activate the code that
allows cacheable PFNMAP.

CC: Oliver Upton <oliver.upton@...ux.dev>
CC: Catalin Marinas <catalin.marinas@....com>
CC: Jason Gunthorpe <jgg@...dia.com>
Suggested-by: Marc Zyngier <maz@...nel.org>
Signed-off-by: Ankit Agrawal <ankita@...dia.com>
---
 include/uapi/linux/kvm.h | 1 +
 virt/kvm/kvm_main.c      | 6 ++++--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index b6ae8ad8934b..9defefe7bdf0 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -51,6 +51,7 @@ struct kvm_userspace_memory_region2 {
 #define KVM_MEM_LOG_DIRTY_PAGES	(1UL << 0)
 #define KVM_MEM_READONLY	(1UL << 1)
 #define KVM_MEM_GUEST_MEMFD	(1UL << 2)
+#define KVM_MEM_ENABLE_CACHEABLE_PFNMAP	(1UL << 3)
 
 /* for KVM_IRQ_LINE */
 struct kvm_irq_level {
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e85b33a92624..a3e77fe57cc4 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1524,12 +1524,14 @@ static void kvm_replace_memslot(struct kvm *kvm,
  * only allows these.
  */
 #define KVM_SET_USER_MEMORY_REGION_V1_FLAGS \
-	(KVM_MEM_LOG_DIRTY_PAGES | KVM_MEM_READONLY)
+	(KVM_MEM_LOG_DIRTY_PAGES | KVM_MEM_READONLY | \
+	 KVM_MEM_ENABLE_CACHEABLE_PFNMAP)
 
 static int check_memory_region_flags(struct kvm *kvm,
 				     const struct kvm_userspace_memory_region2 *mem)
 {
-	u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES;
+	u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES |
+			  KVM_MEM_ENABLE_CACHEABLE_PFNMAP;
 
 	if (kvm_arch_has_private_mem(kvm))
 		valid_flags |= KVM_MEM_GUEST_MEMFD;
-- 
2.34.1