Always use the size of Xen's non-compat vcpu_runstate_info struct when
checking that the GPA+size doesn't cross a page boundary. Conceptually,
using the current mode is more correct, but KVM isn't consistent with
itself as kvm_xen_vcpu_set_attr() unconditionally uses the "full" size
when activating the cache. More importantly, prior to the introduction
of the gfn_to_pfn_cache, KVM _always_ used the full size, i.e. allowing
the guest (userspace?) to use a poorly aligned GPA in 32-bit mode but not
64-bit mode is more of a bug than a feature, and fixing the bug doesn't
break KVM's historical ABI.
Always using the non-compat size will allow for future gfn_to_pfn_cache
clenups as this is (was) the only case where KVM uses a different size at
check()+refresh() than at activate(). E.g. the length/size of the cache
can be made immutable and dropped from check()+refresh(), which yields a
cleaner set of APIs and avoids potential bugs that could occur if check()
where invoked with a different size than refresh().
Fixes: a795cd43c5b5 ("KVM: x86/xen: Use gfn_to_pfn_cache for runstate area")
Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/kvm/xen.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index b2be60c6efa4..9e79ef2cca99 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -212,10 +212,7 @@ void kvm_xen_update_runstate_guest(struct kvm_vcpu *v, int state)
if (!vx->runstate_cache.active)
return;
- if (IS_ENABLED(CONFIG_64BIT) && v->kvm->arch.xen.long_mode)
- user_len = sizeof(struct vcpu_runstate_info);
- else
- user_len = sizeof(struct compat_vcpu_runstate_info);
+ user_len = sizeof(struct vcpu_runstate_info);
read_lock_irqsave(&gpc->lock, flags);
while (!kvm_gfn_to_pfn_cache_check(v->kvm, gpc, gpc->gpa,
--
2.38.0.413.g74048e4d9e-goog
