[PATCH v3 09/11] KVM: x86: Introduce KVM_GET_PAGE_ENC_BITMAP ioctl

[Singh, Brijesh]

The ioctl can be used to retrieve page encryption bitmap for a given
gfn range.

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>
---
 Documentation/virtual/kvm/api.txt | 27 +++++++++++++++++++
 arch/x86/include/asm/kvm_host.h   |  1 +
 arch/x86/kvm/svm.c                | 44 ++++++++++++++++++++++++++++++-
 arch/x86/kvm/x86.c                | 12 +++++++++
 include/uapi/linux/kvm.h          | 12 +++++++++
 5 files changed, 95 insertions(+), 1 deletion(-)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 383b292966fa..ed61a4d63b10 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -4081,6 +4081,33 @@ KVM_ARM_VCPU_FINALIZE call.
 See KVM_ARM_VCPU_INIT for details of vcpu features that require finalization
 using this ioctl.
 
+4.120 KVM_GET_PAGE_ENC_BITMAP (vm ioctl)
+
+Capability: basic
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_page_enc_bitmap (in/out)
+Returns: 0 on success, -1 on error
+
+/* for KVM_GET_PAGE_ENC_BITMAP */
+struct kvm_page_enc_bitmap {
+	__u64 start_gfn;
+	__u64 num_pages;
+	union {
+		void __user *enc_bitmap; /* one bit per page */
+		__u64 padding2;
+	};
+};
+
+The encrypted VMs have concept of private and shared pages. The private
+page is encrypted with the guest-specific key, while shared page may
+be encrypted with the hypervisor key. The KVM_GET_PAGE_ENC_BITMAP can
+be used to get the bitmap indicating whether the guest page is private
+or shared. The bitmap can be used during the guest migration, if the page
+is private then userspace need to use SEV migration commands to transmit
+the page.
+
+
 5. The kvm_run structure
 ------------------------
 
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index b463a81dc176..9df0e2315543 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1201,6 +1201,7 @@ 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 431718309359..e675fd89bb9a 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -7425,6 +7425,47 @@ static int svm_page_enc_status_hc(struct kvm *kvm, unsigned long gpa,
 	return ret;
 }
 
+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;
+	unsigned long *bitmap;
+	unsigned long sz, i;
+	int ret;
+
+	if (!sev_guest(kvm))
+		return -ENOTTY;
+
+	gfn_start = bmap->start_gfn;
+	gfn_end = gfn_start + bmap->num_pages;
+
+	sz = ALIGN(bmap->num_pages, 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;
@@ -7767,7 +7808,8 @@ 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 6baf48ec0ed4..59ae49b1b914 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4927,6 +4927,18 @@ 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 e31cdb41519f..0d08bcf94ef5 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 {
+	__u64 start_gfn;
+	__u64 num_pages;
+	union {
+		void __user *enc_bitmap; /* one bit per page */
+		__u64 padding2;
+	};
+};
+
 /* for KVM_CLEAR_DIRTY_LOG */
 struct kvm_clear_dirty_log {
 	__u32 slot;
@@ -1451,6 +1461,8 @@ struct kvm_enc_region {
 /* Available with KVM_CAP_ARM_SVE */
 #define KVM_ARM_VCPU_FINALIZE	  _IOW(KVMIO,  0xc2, int)
 
+#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