KVM: x86/xen: register shared_info page

We add a new ioctl, XEN_HVM_SHARED_INFO, to allow hypervisor
to know where the guest's shared info page is.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index c9a4feaee2e710245ef9c24ef71976e727419ac5..b6eff9814c6a4455c7158213151adea7d41c1d2d 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -893,6 +893,8 @@ struct msr_bitmap_range {
 /* Xen emulation context */
 struct kvm_xen {
        bool long_mode;
+       struct kvm_host_map shinfo_map;
+       void *shinfo;
 };
 
 enum kvm_irqchip_mode {

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 975ef5d6dda1fb74cdab17829d04b4d8b9f37e9a..4a960629687cd383273e24b108108ec3c32635cb 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10446,6 +10446,7 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
        kvm_mmu_uninit_vm(kvm);
        kvm_page_track_cleanup(kvm);
        kvm_hv_destroy_vm(kvm);
+       kvm_xen_destroy_vm(kvm);
 }
 
 void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)

diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 52cb9e4655421cd57424ff2a74025c322382b928..c156ed1ef9723710ca0db91910221cf3bafe98ce 100644 (file)
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -13,9 +13,51 @@
 #include <linux/kvm_host.h>
 
 #include <trace/events/kvm.h>
+#include <xen/interface/xen.h>
 
 #include "trace.h"
 
+static int kvm_xen_map_guest_page(struct kvm *kvm, struct kvm_host_map *map,
+                                 void **hva, gpa_t gpa, size_t len)
+{
+       gfn_t gfn = gpa_to_gfn(gpa);
+       struct kvm_host_map new_map;
+       bool unmap = !!*hva;
+       int ret;
+
+       if (offset_in_page(gpa) + len > PAGE_SIZE)
+               return -EINVAL;
+
+       ret = kvm_map_gfn(kvm, gfn, &new_map, NULL, false);
+       if (ret)
+               return ret;
+
+       WRITE_ONCE(*hva, new_map.hva + offset_in_page(gpa));
+
+       if (unmap) {
+               synchronize_srcu(&kvm->srcu);
+
+               kvm_unmap_gfn(kvm, map, NULL, true, false);
+       }
+
+       *map = new_map;
+       return 0;
+}
+
+static int kvm_xen_shared_info_init(struct kvm *kvm, gfn_t gfn)
+{
+       gpa_t gpa = gfn_to_gpa(gfn);
+       int ret;
+
+       ret = kvm_xen_map_guest_page(kvm, &kvm->arch.xen.shinfo_map,
+                                    (void **)&kvm->arch.xen.shinfo, gpa,
+                                    PAGE_SIZE);
+       if (ret)
+               return ret;
+
+       return 0;
+}
+
 int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
 {
        int r = -ENOENT;
@@ -28,6 +70,14 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
                kvm->arch.xen.long_mode = !!data->u.long_mode;
                r = 0;
                break;
+
+       case KVM_XEN_ATTR_TYPE_SHARED_INFO: {
+               gfn_t gfn = data->u.shared_info.gfn;
+
+               r = kvm_xen_shared_info_init(kvm, gfn);
+               break;
+       }
+
        default:
                break;
        }
@@ -44,6 +94,15 @@ int kvm_xen_hvm_get_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data)
                data->u.long_mode = kvm->arch.xen.long_mode;
                r = 0;
                break;
+
+       case KVM_XEN_ATTR_TYPE_SHARED_INFO: {
+               if (kvm->arch.xen.shinfo) {
+                       data->u.shared_info.gfn = kvm->arch.xen.shinfo_map.gfn;
+                       r = 0;
+               }
+               break;
+       }
+
        default:
                break;
        }
@@ -182,3 +241,13 @@ int kvm_xen_hypercall(struct kvm_vcpu *vcpu)
 
        return 0;
 }
+
+void kvm_xen_destroy_vm(struct kvm *kvm)
+{
+       struct kvm_xen *xen = &kvm->arch.xen;
+
+       if (xen->shinfo) {
+               kvm_unmap_gfn(kvm, &xen->shinfo_map, NULL, true, false);
+               xen->shinfo = NULL;
+       }
+}

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 6b556ef98b767016f583837d8ce126a2ed686750..caa9faf3c5adbca136b8fb103a6a871571010ce4 100644 (file)
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1585,11 +1585,15 @@ struct kvm_xen_hvm_attr {
 
        union {
                __u8 long_mode;
+               struct {
+                       __u64 gfn;
+               } shared_info;
                __u64 pad[4];
        } u;
 };
 
 #define KVM_XEN_ATTR_TYPE_LONG_MODE            0x0
+#define KVM_XEN_ATTR_TYPE_SHARED_INFO          0x1
 
 /* Secure Encrypted Virtualization command */
 enum sev_cmd_id {