On 11/11/2023 2:22 AM, Sean Christopherson wrote:
On Fri, Nov 10, 2023, Xiaoyao Li wrote:
On 11/6/2023 12:30 AM, Paolo Bonzini wrote:
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 68a144cb7dbc..a6de526c0426 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -589,8 +589,20 @@ struct kvm_memory_slot {
u32 flags;
short id;
u16 as_id;
+
+#ifdef CONFIG_KVM_PRIVATE_MEM
+ struct {
+ struct file __rcu *file;
+ pgoff_t pgoff;
+ } gmem;
+#endif
};
+static inline bool kvm_slot_can_be_private(const struct kvm_memory_slot *slot)
+{
+ return slot && (slot->flags & KVM_MEM_GUEST_MEMFD);
+}
+
maybe we can move this block and ...
<snip>
@@ -2355,6 +2379,30 @@ bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm,
struct kvm_gfn_range *range);
bool kvm_arch_post_set_memory_attributes(struct kvm *kvm,
struct kvm_gfn_range *range);
+
+static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
+{
+ return IS_ENABLED(CONFIG_KVM_PRIVATE_MEM) &&
+ kvm_get_memory_attributes(kvm, gfn) & KVM_MEMORY_ATTRIBUTE_PRIVATE;
+}
+#else
+static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
+{
+ return false;
+}
#endif /* CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES */
this block to Patch 18?
It would work, but my vote is to keep them here to minimize the changes to common
KVM code in the x86 enabling. It's not a strong preference though. Of course,
at this point, fiddling with this sort of thing is probably a bad idea in terms
of landing guest_memfd.
Indeed. It's OK then.
@@ -4844,6 +4875,10 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
case KVM_CAP_MEMORY_ATTRIBUTES:
return kvm_supported_mem_attributes(kvm);
+#endif
+#ifdef CONFIG_KVM_PRIVATE_MEM
+ case KVM_CAP_GUEST_MEMFD:
+ return !kvm || kvm_arch_has_private_mem(kvm);
#endif
default:
break;
@@ -5277,6 +5312,18 @@ static long kvm_vm_ioctl(struct file *filp,
case KVM_GET_STATS_FD:
r = kvm_vm_ioctl_get_stats_fd(kvm);
break;
+#ifdef CONFIG_KVM_PRIVATE_MEM
+ case KVM_CREATE_GUEST_MEMFD: {
+ struct kvm_create_guest_memfd guest_memfd;
Do we need a guard of below?
r = -EINVAL;
if (!kvm_arch_has_private_mem(kvm))
goto out;
Argh, yeah, that's weird since KVM_CAP_GUEST_MEMFD says "not supported" if the
VM doesn't support private memory.
Enforcing that would break guest_memfd_test.c though. And having to create a
"special" VM just to test basic guest_memfd functionality would be quite
annoying.
So my vote is to do:
case KVM_CAP_GUEST_MEMFD:
return IS_ENABLED(CONFIG_KVM_PRIVATE_MEM);
I'm fine with it.
There's no harm to KVM if userspace creates a file it can't use, and at some
point KVM will hopefully support guest_memfd irrespective of private memory.
