linux-kernel - [RFC 26/33] KVM: x86: hyper-vsm: Allow setting per-VTL memory attributes

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Message-ID: <20231108111806.92604-27-nsaenz@amazon.com>
Date:   Wed, 8 Nov 2023 11:17:59 +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 26/33] KVM: x86: hyper-vsm: Allow setting per-VTL memory attributes

Introduce KVM_SET_MEMORY_ATTRIBUTES ioctl support for VTL KVM devices.
The attributes are stored in an xarray private to the VTL device.

The following memory attributes are supported:
 - KVM_MEMORY_ATTRIBUTE_READ
 - KVM_MEMORY_ATTRIBUTE_WRITE
 - KVM_MEMORY_ATTRIBUTE_EXECUTE
 - KVM_MEMORY_ATTRIBUTE_NO_ACCESS
Although only some combinations are valid, see code comment below.

Signed-off-by: Nicolas Saenz Julienne <nsaenz@...zon.com>
---
 arch/x86/kvm/hyperv.c | 61 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 0d8402dba596..bcace0258af1 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -62,6 +62,10 @@
  */
 #define HV_EXT_CALL_MAX (HV_EXT_CALL_QUERY_CAPABILITIES + 64)
 
+#define KVM_HV_VTL_ATTRS						\
+	(KVM_MEMORY_ATTRIBUTE_READ | KVM_MEMORY_ATTRIBUTE_WRITE |	\
+	 KVM_MEMORY_ATTRIBUTE_EXECUTE | KVM_MEMORY_ATTRIBUTE_NO_ACCESS)
+
 static void stimer_mark_pending(struct kvm_vcpu_hv_stimer *stimer,
 				bool vcpu_kick);
 
@@ -3025,6 +3029,7 @@ int kvm_vm_ioctl_get_hv_vsm_state(struct kvm *kvm, struct kvm_hv_vsm_state *stat
 
 struct kvm_hv_vtl_dev {
 	int vtl;
+	struct xarray mem_attrs;
 };
 
 static int kvm_hv_vtl_get_attr(struct kvm_device *dev,
@@ -3047,16 +3052,71 @@ static void kvm_hv_vtl_release(struct kvm_device *dev)
 {
 	struct kvm_hv_vtl_dev *vtl_dev = dev->private;
 
+	xa_destroy(&vtl_dev->mem_attrs);
 	kfree(vtl_dev);
 	kfree(dev); /* alloc by kvm_ioctl_create_device, free by .release */
 }
 
+/*
+ * The TLFS lists the valid memory protection combinations (15.9.3):
+ *  - No access
+ *  - Read-only, no execute
+ *  - Read-only, execute
+ *  - Read/write, no execute
+ *  - Read/write, execute
+ */
+static bool kvm_hv_validate_vtl_mem_attributes(struct kvm_memory_attributes *attrs)
+{
+	u64 attr = attrs->attributes;
+
+	if (attr & ~KVM_HV_VTL_ATTRS)
+		return false;
+
+	if (attr == KVM_MEMORY_ATTRIBUTE_NO_ACCESS)
+		return true;
+
+	if (!(attr & KVM_MEMORY_ATTRIBUTE_READ))
+		return false;
+
+	return true;
+}
+
+static long kvm_hv_vtl_ioctl(struct kvm_device *dev, unsigned int ioctl,
+			     unsigned long arg)
+{
+	switch (ioctl) {
+	case KVM_SET_MEMORY_ATTRIBUTES: {
+		struct kvm_hv_vtl_dev *vtl_dev = dev->private;
+		struct kvm_memory_attributes attrs;
+		int r;
+
+		if (copy_from_user(&attrs, (void __user *)arg, sizeof(attrs)))
+			return -EFAULT;
+
+		r = -EINVAL;
+		if (!kvm_hv_validate_vtl_mem_attributes(&attrs))
+			return r;
+
+		r = kvm_ioctl_set_mem_attributes(dev->kvm, &vtl_dev->mem_attrs,
+						 KVM_HV_VTL_ATTRS, &attrs);
+		if (r)
+			return r;
+		break;
+	}
+	default:
+		return -ENOTTY;
+	}
+
+	return 0;
+}
+
 static int kvm_hv_vtl_create(struct kvm_device *dev, u32 type);
 
 static struct kvm_device_ops kvm_hv_vtl_ops = {
 	.name = "kvm-hv-vtl",
 	.create = kvm_hv_vtl_create,
 	.release = kvm_hv_vtl_release,
+	.ioctl = kvm_hv_vtl_ioctl,
 	.get_attr = kvm_hv_vtl_get_attr,
 };
 
@@ -3076,6 +3136,7 @@ static int kvm_hv_vtl_create(struct kvm_device *dev, u32 type)
 			vtl++;
 
 	vtl_dev->vtl = vtl;
+	xa_init(&vtl_dev->mem_attrs);
 	dev->private = vtl_dev;
 
 	return 0;
-- 
2.40.1