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Subject[PATCH 09/12] KVM: x86: Introduce KVM_GET_PAGE_ENC_BITMAP ioctl
Date
From: Brijesh Singh <brijesh.singh@amd.com>

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

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: x86@kernel.org
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
---
Documentation/virt/kvm/api.txt | 27 +++++++++++++++++++++
arch/x86/include/asm/kvm_host.h | 2 ++
arch/x86/kvm/svm.c | 43 +++++++++++++++++++++++++++++++++
arch/x86/kvm/x86.c | 12 +++++++++
include/uapi/linux/kvm.h | 12 +++++++++
5 files changed, 96 insertions(+)

diff --git a/Documentation/virt/kvm/api.txt b/Documentation/virt/kvm/api.txt
index c6e1ce5d40de..053aecfabe74 100644
--- a/Documentation/virt/kvm/api.txt
+++ b/Documentation/virt/kvm/api.txt
@@ -4213,6 +4213,33 @@ the clear cpu reset definition in the POP. However, the cpu is not put
into ESA mode. This reset is a superset of the initial reset.


+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 4ae7293033b2..a6882c5214b4 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1258,6 +1258,8 @@ struct kvm_x86_ops {
int (*enable_direct_tlbflush)(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 f09791109075..f1c8806a97c6 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -7673,6 +7673,48 @@ 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;
+
+ /* by default all pages are marked encrypted */
+ memset(bitmap, 0xff, sz);
+
+ 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;
@@ -8066,6 +8108,7 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
.apic_init_signal_blocked = svm_apic_init_signal_blocked,

.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 298627fa3d39..e955f886ee17 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5213,6 +5213,18 @@ long kvm_arch_vm_ioctl(struct file *filp,
case KVM_SET_PMU_EVENT_FILTER:
r = kvm_vm_ioctl_set_pmu_event_filter(kvm, argp);
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 4e80c57a3182..9377b26c5f4e 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -500,6 +500,16 @@ 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;
@@ -1478,6 +1488,8 @@ struct kvm_enc_region {
#define KVM_S390_NORMAL_RESET _IO(KVMIO, 0xc3)
#define KVM_S390_CLEAR_RESET _IO(KVMIO, 0xc4)

+#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
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