Messages in this thread | | | Date | Sat, 21 Mar 2020 12:22:11 -0700 | From | Sean Christopherson <> | Subject | Re: [PATCH v7 03/14] KVM: X86: Don't track dirty for KVM_SET_[TSS_ADDR|IDENTITY_MAP_ADDR] |
| |
On Wed, Mar 18, 2020 at 12:37:09PM -0400, Peter Xu wrote: > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index e54c6ad628a8..a5123a0aa7d6 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -9786,7 +9786,34 @@ void kvm_arch_sync_events(struct kvm *kvm) > kvm_free_pit(kvm); > } > > -int __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, u32 size) > +#define ERR_PTR_USR(e) ((void __user *)ERR_PTR(e)) > + > +/** > + * __x86_set_memory_region: Setup KVM internal memory slot > + * > + * @kvm: the kvm pointer to the VM. > + * @id: the slot ID to setup. > + * @gpa: the GPA to install the slot (unused when @size == 0). > + * @size: the size of the slot. Set to zero to uninstall a slot. > + * > + * This function helps to setup a KVM internal memory slot. Specify > + * @size > 0 to install a new slot, while @size == 0 to uninstall a > + * slot. The return code can be one of the following: > + * > + * HVA: on success (uninstall will return a bogus HVA) > + * -errno: on error > + * > + * The caller should always use IS_ERR() to check the return value > + * before use. NOTE: KVM internal memory slots are guaranteed and
"are guaranteed" to ...
> + * won't change until the VM is destroyed. This is also true to the > + * returned HVA when installing a new memory slot. The HVA can be > + * invalidated by either an errornous userspace program or a VM under > + * destruction, however as long as we use __copy_{to|from}_user() > + * properly upon the HVAs and handle the failure paths always then > + * we're safe.
Regarding the HVA, it's a bit confusing saying that it's guaranteed to be valid, and then contradicting that in the second clause. Maybe something like this to explain the GPA->HVA is guaranteed to be valid, but the HVA->HPA is not.
/* * before use. Note, KVM internal memory slots are guaranteed to remain valid * and unchanged until the VM is destroyed, i.e. the GPA->HVA translation will * not change. However, the HVA is a user address, i.e. its accessibility is * not guaranteed, and must be accessed via __copy_{to,from}_user(). */
| |