[Qemu-devel] [RFC PATCH v1 08/10] KVM: X86: Introduce KVM_HC_PAGE_ENC_STATUS hypercall

[Singh, Brijesh]

The hypercall can be used by the SEV guest to notify 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 the guest pages should be considered encrypted.

Cc: Thomas Gleixner <address@hidden>
Cc: Ingo Molnar <address@hidden>
Cc: "H. Peter Anvin" <address@hidden>
Cc: Paolo Bonzini <address@hidden>
Cc: "Radim Krčmář" <address@hidden>
Cc: Joerg Roedel <address@hidden>
Cc: Borislav Petkov <address@hidden>
Cc: Tom Lendacky <address@hidden>
Cc: address@hidden
Cc: address@hidden
Cc: address@hidden
Signed-off-by: Brijesh Singh <address@hidden>
---
 Documentation/virtual/kvm/hypercalls.txt | 14 +++++
 arch/x86/include/asm/kvm_host.h          |  2 +
 arch/x86/kvm/svm.c                       | 69 ++++++++++++++++++++++++
 arch/x86/kvm/vmx/vmx.c                   |  1 +
 arch/x86/kvm/x86.c                       |  5 ++
 include/uapi/linux/kvm_para.h            |  1 +
 6 files changed, 92 insertions(+)

diff --git a/Documentation/virtual/kvm/hypercalls.txt 
b/Documentation/virtual/kvm/hypercalls.txt
index da24c138c8d1..ecd44e488679 100644
--- a/Documentation/virtual/kvm/hypercalls.txt
+++ b/Documentation/virtual/kvm/hypercalls.txt
@@ -141,3 +141,17 @@ a0 corresponds to the APIC ID in the third argument (a2), 
bit 1
 corresponds to the APIC ID a2+1, and so on.
 
 Returns the number of CPUs to which the IPIs were delivered successfully.
+
+7. 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: set or clear the 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 a9d03af34030..adb0ca035b97 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1196,6 +1196,8 @@ struct kvm_x86_ops {
        uint16_t (*nested_get_evmcs_version)(struct kvm_vcpu *vcpu);
 
        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);
 };
 
 struct kvm_arch_async_pf {
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 74b57ab742ad..f024f208b052 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -138,6 +138,8 @@ 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 {
@@ -1911,6 +1913,8 @@ static void sev_vm_destroy(struct kvm *kvm)
 
        sev_unbind_asid(kvm, sev->handle);
        sev_asid_free(kvm);
+
+       kvfree(sev->page_enc_bmap);
 }
 
 static void avic_vm_destroy(struct kvm *kvm)
@@ -7370,6 +7374,69 @@ 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;
+
+       if (sz > PAGE_SIZE)
+               map = vmalloc(sz);
+       else
+               map = kmalloc(sz, GFP_KERNEL);
+
+       if (!map) {
+               pr_err_once("Failed to allocate decrypted bitmap size %lx\n", 
sz);
+               return 1;
+       }
+
+       /* 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;
+       gfn_t gfn_start, gfn_end;
+       int r;
+
+       if (!npages)
+               return 0;
+
+       gfn_start = gpa_to_gfn(gpa);
+       gfn_end = gfn_start + npages;
+
+       mutex_lock(&kvm->lock);
+
+       r = 1;
+       if (sev_resize_page_enc_bitmap(kvm, 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);
+
+       r = 0;
+unlock:
+       mutex_unlock(&kvm->lock);
+       return r;
+}
+
 static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
 {
        struct kvm_sev_cmd sev_cmd;
@@ -7711,6 +7778,8 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
        .nested_get_evmcs_version = nested_get_evmcs_version,
 
        .need_emulation_on_page_fault = svm_need_emulation_on_page_fault,
+
+       .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 b4e7d645275a..9c814e560e0f 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7731,6 +7731,7 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
        .get_vmcs12_pages = NULL,
        .nested_enable_evmcs = NULL,
        .need_emulation_on_page_fault = vmx_need_emulation_on_page_fault,
+       .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 a0d1fc80ac5a..dea644be5992 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7141,6 +7141,11 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
        case KVM_HC_SEND_IPI:
                ret = kvm_pv_send_ipi(vcpu->kvm, a0, a1, a2, a3, op_64_bit);
                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 6c0ce49931e5..3dc9e579f4f9 100644
--- a/include/uapi/linux/kvm_para.h
+++ b/include/uapi/linux/kvm_para.h
@@ -28,6 +28,7 @@
 #define KVM_HC_MIPS_CONSOLE_OUTPUT     8
 #define KVM_HC_CLOCK_PAIRING           9
 #define KVM_HC_SEND_IPI                10
+#define KVM_HC_PAGE_ENC_STATUS         11
 
 /*
  * hypercalls use architecture specific
-- 
2.17.1