[PATCH v6 08/14] KVM: X86: Introduce KVM_HC_PAGE_ENC_STATUS hypercall

[Ashish Kalra <Ashish.Kalra@amd.com>]

From: Brijesh Singh <Brijesh.Singh@amd.com>

This hypercall is used by the SEV guest to notify a change in the page
encryption status to the hypervisor. The hypercall should be invoked
only when the encryption attribute is changed from encrypted -> decrypted
and vice versa. By default all guest pages are considered encrypted.

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/hypercalls.rst | 15 +++++
 arch/x86/include/asm/kvm_host.h       |  2 +
 arch/x86/kvm/svm.c                    | 95 +++++++++++++++++++++++++++
 arch/x86/kvm/vmx/vmx.c                |  1 +
 arch/x86/kvm/x86.c                    |  6 ++
 include/uapi/linux/kvm_para.h         |  1 +
 6 files changed, 120 insertions(+)

diff --git a/Documentation/virt/kvm/hypercalls.rst b/Documentation/virt/kvm/hypercalls.rst
index dbaf207e560d..ff5287e68e81 100644
--- a/Documentation/virt/kvm/hypercalls.rst
+++ b/Documentation/virt/kvm/hypercalls.rst
@@ -169,3 +169,18 @@ a0: destination APIC ID
 
 :Usage example: When sending a call-function IPI-many to vCPUs, yield if
 	        any of the IPI target vCPUs was preempted.
+
+
+8. KVM_HC_PAGE_ENC_STATUS
+-------------------------
+:Architecture: x86
+:Status: active
+:Purpose: Notify the encryption status changes in guest page table (SEV guest)
+
+a0: the guest physical address of the start page
+a1: the number of pages
+a2: encryption attribute
+
+   Where:
+	* 1: Encryption attribute is set
+	* 0: Encryption attribute is cleared
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 98959e8cd448..90718fa3db47 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1267,6 +1267,8 @@ struct kvm_x86_ops {
 
 	bool (*apic_init_signal_blocked)(struct kvm_vcpu *vcpu);
 	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);
 };
 
 struct kvm_arch_async_pf {
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 7c2721e18b06..1d8beaf1bceb 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -136,6 +136,8 @@ struct kvm_sev_info {
 	int fd;			/* SEV device fd */
 	unsigned long pages_locked; /* Number of pages locked */
 	struct list_head regions_list;  /* List of registered regions */
+	unsigned long *page_enc_bmap;
+	unsigned long page_enc_bmap_size;
 };
 
 struct kvm_svm {
@@ -1991,6 +1993,9 @@ static void sev_vm_destroy(struct kvm *kvm)
 
 	sev_unbind_asid(kvm, sev->handle);
 	sev_asid_free(sev->asid);
+
+	kvfree(sev->page_enc_bmap);
+	sev->page_enc_bmap = NULL;
 }
 
 static void avic_vm_destroy(struct kvm *kvm)
@@ -7593,6 +7598,94 @@ static int sev_receive_finish(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	return ret;
 }
 
+static int sev_resize_page_enc_bitmap(struct kvm *kvm, unsigned long new_size)
+{
+	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+	unsigned long *map;
+	unsigned long sz;
+
+	if (sev->page_enc_bmap_size >= new_size)
+		return 0;
+
+	sz = ALIGN(new_size, BITS_PER_LONG) / 8;
+
+	map = vmalloc(sz);
+	if (!map) {
+		pr_err_once("Failed to allocate encrypted bitmap size %lx\n",
+				sz);
+		return -ENOMEM;
+	}
+
+	/* mark the page encrypted (by default) */
+	memset(map, 0xff, sz);
+
+	bitmap_copy(map, sev->page_enc_bmap, sev->page_enc_bmap_size);
+	kvfree(sev->page_enc_bmap);
+
+	sev->page_enc_bmap = map;
+	sev->page_enc_bmap_size = new_size;
+
+	return 0;
+}
+
+static int svm_page_enc_status_hc(struct kvm *kvm, unsigned long gpa,
+				  unsigned long npages, unsigned long enc)
+{
+	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+	kvm_pfn_t pfn_start, pfn_end;
+	gfn_t gfn_start, gfn_end;
+	int ret;
+
+	if (!sev_guest(kvm))
+		return -EINVAL;
+
+	if (!npages)
+		return 0;
+
+	gfn_start = gpa_to_gfn(gpa);
+	gfn_end = gfn_start + npages;
+
+	/* out of bound access error check */
+	if (gfn_end <= gfn_start)
+		return -EINVAL;
+
+	/* lets make sure that gpa exist in our memslot */
+	pfn_start = gfn_to_pfn(kvm, gfn_start);
+	pfn_end = gfn_to_pfn(kvm, gfn_end);
+
+	if (is_error_noslot_pfn(pfn_start) && !is_noslot_pfn(pfn_start)) {
+		/*
+		 * Allow guest MMIO range(s) to be added
+		 * to the page encryption bitmap.
+		 */
+		return -EINVAL;
+	}
+
+	if (is_error_noslot_pfn(pfn_end) && !is_noslot_pfn(pfn_end)) {
+		/*
+		 * Allow guest MMIO range(s) to be added
+		 * to the page encryption bitmap.
+		 */
+		return -EINVAL;
+	}
+
+	mutex_lock(&kvm->lock);
+	ret = sev_resize_page_enc_bitmap(kvm, gfn_end);
+	if (ret)
+		goto unlock;
+
+	if (enc)
+		__bitmap_set(sev->page_enc_bmap, gfn_start,
+				gfn_end - gfn_start);
+	else
+		__bitmap_clear(sev->page_enc_bmap, gfn_start,
+				gfn_end - gfn_start);
+
+unlock:
+	mutex_unlock(&kvm->lock);
+	return ret;
+}
+
 static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
 {
 	struct kvm_sev_cmd sev_cmd;
@@ -7995,6 +8088,8 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
 	.need_emulation_on_page_fault = svm_need_emulation_on_page_fault,
 
 	.apic_init_signal_blocked = svm_apic_init_signal_blocked,
+
+	.page_enc_status_hc = svm_page_enc_status_hc,
 };
 
 static int __init svm_init(void)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 079d9fbf278e..f68e76ee7f9c 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -8001,6 +8001,7 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
 	.nested_get_evmcs_version = NULL,
 	.need_emulation_on_page_fault = vmx_need_emulation_on_page_fault,
 	.apic_init_signal_blocked = vmx_apic_init_signal_blocked,
+	.page_enc_status_hc = NULL,
 };
 
 static void vmx_cleanup_l1d_flush(void)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index cf95c36cb4f4..68428eef2dde 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7564,6 +7564,12 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
 		kvm_sched_yield(vcpu->kvm, a0);
 		ret = 0;
 		break;
+	case KVM_HC_PAGE_ENC_STATUS:
+		ret = -KVM_ENOSYS;
+		if (kvm_x86_ops->page_enc_status_hc)
+			ret = kvm_x86_ops->page_enc_status_hc(vcpu->kvm,
+					a0, a1, a2);
+		break;
 	default:
 		ret = -KVM_ENOSYS;
 		break;
diff --git a/include/uapi/linux/kvm_para.h b/include/uapi/linux/kvm_para.h
index 8b86609849b9..847b83b75dc8 100644
--- a/include/uapi/linux/kvm_para.h
+++ b/include/uapi/linux/kvm_para.h
@@ -29,6 +29,7 @@
 #define KVM_HC_CLOCK_PAIRING		9
 #define KVM_HC_SEND_IPI		10
 #define KVM_HC_SCHED_YIELD		11
+#define KVM_HC_PAGE_ENC_STATUS		12
 
 /*
  * hypercalls use architecture specific
-- 
2.17.1