[RFC PATCH v1 09/10] KVM: x86: Introduce KVM_GET_PAGE_ENC_BITMAP ioctl

[Singh, Brijesh]

The ioctl can be used to retrieve page encryption bitmap for a given
kvm memory slot.

Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: "Radim KrÄmÃÅ" <rkrcmar@xxxxxxxxxx>
Cc: Joerg Roedel <joro@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: kvm@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
---
 arch/x86/include/asm/kvm_host.h |  1 +
 arch/x86/kvm/svm.c              | 54 ++++++++++++++++++++++++++++++++-
 arch/x86/kvm/x86.c              | 12 ++++++++
 include/uapi/linux/kvm.h        | 12 ++++++++
 4 files changed, 78 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index adb0ca035b97..9947c4be825d 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1198,6 +1198,7 @@ struct kvm_x86_ops {
 	bool (*need_emulation_on_page_fault)(struct kvm_vcpu *vcpu);
 	int (*page_enc_status_hc)(struct kvm *kvm, unsigned long gpa,
 				  unsigned long sz, unsigned long mode);
+	int (*get_page_enc_bitmap)(struct kvm *kvm, struct kvm_page_enc_bitmap *bmap);
 };
 
 struct kvm_arch_async_pf {
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index f024f208b052..f386d72c929b 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -7437,6 +7437,57 @@ static int svm_page_enc_status_hc(struct kvm *kvm, unsigned long gpa,
 	return r;
 }
 
+static int svm_get_page_enc_bitmap(struct kvm *kvm,
+				   struct kvm_page_enc_bitmap *bmap)
+{
+	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+	unsigned long gfn_start, gfn_end;
+	struct kvm_memory_slot *memslot;
+	struct kvm_memslots *slots;
+	unsigned long *bitmap;
+	unsigned long sz, i;
+	int ret, as_id, id;
+
+	if (!sev_guest(kvm))
+		return -ENOTTY;
+
+	as_id = bmap->slot >> 16;
+	id = (u16)bmap->slot;
+	if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_USER_MEM_SLOTS)
+		return -EINVAL;
+
+	slots = __kvm_memslots(kvm, as_id);
+	memslot = id_to_memslot(slots, id);
+
+	gfn_start = memslot->base_gfn;
+	gfn_end = gfn_start + memslot->npages;
+
+	sz = ALIGN(memslot->npages, BITS_PER_LONG) / 8;
+	bitmap = kmalloc(sz, GFP_KERNEL);
+	if (!bitmap)
+		return -ENOMEM;
+
+	memset(bitmap, 0xff, sz); /* by default all pages are marked encrypted */
+
+	mutex_lock(&kvm->lock);
+	if (sev->page_enc_bmap) {
+		i = gfn_start;
+		for_each_clear_bit_from(i, sev->page_enc_bmap,
+				      min(sev->page_enc_bmap_size, gfn_end))
+			clear_bit(i - gfn_start, bitmap);
+	}
+	mutex_unlock(&kvm->lock);
+
+	ret = -EFAULT;
+	if (copy_to_user(bmap->enc_bitmap, bitmap, sz))
+		goto out;
+
+	ret = 0;
+out:
+	kfree(bitmap);
+	return ret;
+}
+
 static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
 {
 	struct kvm_sev_cmd sev_cmd;
@@ -7779,7 +7830,8 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
 
 	.need_emulation_on_page_fault = svm_need_emulation_on_page_fault,
 
-	.page_enc_status_hc = svm_page_enc_status_hc
+	.page_enc_status_hc = svm_page_enc_status_hc,
+	.get_page_enc_bitmap = svm_get_page_enc_bitmap
 };
 
 static int __init svm_init(void)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index dea644be5992..44079979b1c5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4882,6 +4882,18 @@ long kvm_arch_vm_ioctl(struct file *filp,
 		r = kvm_vm_ioctl_hv_eventfd(kvm, &hvevfd);
 		break;
 	}
+	case KVM_GET_PAGE_ENC_BITMAP: {
+		struct kvm_page_enc_bitmap bitmap;
+
+		r = -EFAULT;
+		if (copy_from_user(&bitmap, argp, sizeof(bitmap)))
+			goto out;
+
+		r = -ENOTTY;
+		if (kvm_x86_ops->get_page_enc_bitmap)
+			r = kvm_x86_ops->get_page_enc_bitmap(kvm, &bitmap);
+		break;
+	}
 	default:
 		r = -ENOTTY;
 	}
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 07e058a3ec11..7f944d4e252c 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -492,6 +492,16 @@ struct kvm_dirty_log {
 	};
 };
 
+/* for KVM_GET_PAGE_ENC_BITMAP */
+struct kvm_page_enc_bitmap {
+	__u32 slot;
+	__u32 padding1;
+	union {
+		void __user *enc_bitmap; /* one bit per page */
+		__u64 padding2;
+	};
+};
+
 /* for KVM_CLEAR_DIRTY_LOG */
 struct kvm_clear_dirty_log {
 	__u32 slot;
@@ -1440,6 +1450,8 @@ struct kvm_enc_region {
 /* Available with KVM_CAP_HYPERV_CPUID */
 #define KVM_GET_SUPPORTED_HV_CPUID _IOWR(KVMIO, 0xc1, struct kvm_cpuid2)
 
+#define KVM_GET_PAGE_ENC_BITMAP	_IOW(KVMIO, 0xc2, struct kvm_page_enc_bitmap)
+
 /* Secure Encrypted Virtualization command */
 enum sev_cmd_id {
 	/* Guest initialization commands */
-- 
2.17.1