[PATCH v8 08/18] KVM: X86: Introduce KVM_HC_PAGE_ENC_STATUS hypercall

Ashish Kalra
2020-05-05T21:17:38Z

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
Reviewed-by: Venu Busireddy <venu.busireddy@oracle.com>
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/sev.c | 90 +++++++++++++++++++++++++++
arch/x86/kvm/svm/svm.c | 2 +
arch/x86/kvm/svm/svm.h | 4 ++
arch/x86/kvm/vmx/vmx.c | 1 +
arch/x86/kvm/x86.c | 6 ++
include/uapi/linux/kvm_para.h | 1 +
8 files changed, 121 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 42a2d0d3984a..4a8ee22f4f5b 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1254,6 +1254,8 @@ 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_x86_init_ops {
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 698704defbcd..f088467708f0 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1347,6 +1347,93 @@ 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;
+}
+
+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;
+
+ 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);
+
+ if (sev->page_enc_bmap_size < gfn_end)
+ 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 0;
+}
+
int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
{
struct kvm_sev_cmd sev_cmd;
@@ -1560,6 +1647,9 @@ 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;
}

int __init sev_hardware_setup(void)
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 2f379bacbb26..1013ef0f4ce2 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4014,6 +4014,8 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
.apic_init_signal_blocked = svm_apic_init_signal_blocked,

.check_nested_events = svm_check_nested_events,
+
+ .page_enc_status_hc = svm_page_enc_status_hc,
};

static struct kvm_x86_init_ops svm_init_ops __initdata = {
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index df3474f4fb02..6a562f5928a2 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -65,6 +65,8 @@ 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 {
@@ -400,6 +402,8 @@ int nested_svm_check_exception(struct vcpu_svm *svm, unsigned nr,
bool has_error_code, u32 error_code);
int svm_check_nested_events(struct kvm_vcpu *vcpu);
int nested_svm_exit_special(struct vcpu_svm *svm);
+int svm_page_enc_status_hc(struct kvm *kvm, unsigned long gpa,
+ unsigned long npages, unsigned long enc);

/* avic.c */

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index c2c6335a998c..7d01d3aa6461 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7838,6 +7838,7 @@ static struct kvm_x86_ops vmx_x86_ops __initdata = {
.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 __init int hardware_setup(void)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c5835f9cb9ad..5f5ddb5765e2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7605,6 +7605,12 @@ 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