linux-kernel - [RFC 16/33] KVM: x86/mmu: Expose R/W/X flags during memory fault exits

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Date:   Wed, 8 Nov 2023 11:17:49 +0000
From:   Nicolas Saenz Julienne <nsaenz@...zon.com>
To:     <kvm@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-hyperv@...r.kernel.org>,
        <pbonzini@...hat.com>, <seanjc@...gle.com>, <vkuznets@...hat.com>,
        <anelkz@...zon.com>, <graf@...zon.com>, <dwmw@...zon.co.uk>,
        <jgowans@...zon.com>, <corbert@....net>, <kys@...rosoft.com>,
        <haiyangz@...rosoft.com>, <decui@...rosoft.com>, <x86@...nel.org>,
        <linux-doc@...r.kernel.org>,
        Nicolas Saenz Julienne <nsaenz@...zon.com>
Subject: [RFC 16/33] KVM: x86/mmu: Expose R/W/X flags during memory fault exits

Include the fault's read, write and execute status when exiting to
user-space.

Signed-off-by: Nicolas Saenz Julienne <nsaenz@...zon.com>
---
 arch/x86/kvm/mmu/mmu.c   | 4 ++--
 include/linux/kvm_host.h | 9 +++++++--
 include/uapi/linux/kvm.h | 6 ++++++
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 4e02d506cc25..feca077c0210 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4300,8 +4300,8 @@ static inline u8 kvm_max_level_for_order(int order)
 static void kvm_mmu_prepare_memory_fault_exit(struct kvm_vcpu *vcpu,
 					      struct kvm_page_fault *fault)
 {
-	kvm_prepare_memory_fault_exit(vcpu, fault->gfn << PAGE_SHIFT,
-				      PAGE_SIZE, fault->write, fault->exec,
+	kvm_prepare_memory_fault_exit(vcpu, fault->gfn << PAGE_SHIFT, PAGE_SIZE,
+				      fault->write, fault->exec, fault->user,
 				      fault->is_private);
 }
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 71e1e8cf8936..631fd532c97a 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2367,14 +2367,19 @@ static inline void kvm_account_pgtable_pages(void *virt, int nr)
 static inline void kvm_prepare_memory_fault_exit(struct kvm_vcpu *vcpu,
 						 gpa_t gpa, gpa_t size,
 						 bool is_write, bool is_exec,
-						 bool is_private)
+						 bool is_read, bool is_private)
 {
 	vcpu->run->exit_reason = KVM_EXIT_MEMORY_FAULT;
 	vcpu->run->memory_fault.gpa = gpa;
 	vcpu->run->memory_fault.size = size;
 
-	/* RWX flags are not (yet) defined or communicated to userspace. */
 	vcpu->run->memory_fault.flags = 0;
+	if (is_read)
+		vcpu->run->memory_fault.flags |= KVM_MEMORY_EXIT_FLAG_READ;
+	if (is_write)
+		vcpu->run->memory_fault.flags |= KVM_MEMORY_EXIT_FLAG_WRITE;
+	if (is_exec)
+		vcpu->run->memory_fault.flags |= KVM_MEMORY_EXIT_FLAG_EXECUTE;
 	if (is_private)
 		vcpu->run->memory_fault.flags |= KVM_MEMORY_EXIT_FLAG_PRIVATE;
 }
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 03f5c08fd7aa..0ddffb8b0c99 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -533,7 +533,13 @@ struct kvm_run {
 		} notify;
 		/* KVM_EXIT_MEMORY_FAULT */
 		struct {
+#define KVM_MEMORY_EXIT_FLAG_READ	(1ULL << 0)
+#define KVM_MEMORY_EXIT_FLAG_WRITE	(1ULL << 1)
+#define KVM_MEMORY_EXIT_FLAG_EXECUTE	(1ULL << 2)
 #define KVM_MEMORY_EXIT_FLAG_PRIVATE	(1ULL << 3)
+#define KVM_MEMORY_EXIT_NO_ACCESS                            \
+	(KVM_MEMORY_EXIT_FLAG_NR | KVM_MEMORY_EXIT_FLAG_NW | \
+	 KVM_MEMORY_EXIT_FLAG_NX)
 			__u64 flags;
 			__u64 gpa;
 			__u64 size;
-- 
2.40.1