On 13/10/2015 17:39, Radim Krčmář wrote:
> 2015-10-12 14:09+0200, Paolo Bonzini:
>> Otherwise, two copies (one of them never used and thus bogus) are
>> allocated for the regular and SMM address spaces. This breaks
>> SMM with EPT but without unrestricted guest support, because the
>> SMM copy of the identity page map is all zeros.
>
> (Have you found out why EPT+unrestricted didn't use the alternative SMM
> mapping as well?)
Yes, that I already knew; EPT+unrestricted uses CR0.PG=0 directly so
it doesn't use the identity page at all. (CR0.PG=0 w/o unrestricted
instead runs with CR0.PG=1. CR3 load and store exits are enabled,
and the guest CR3 always points to the identity page map while the
guest runs).
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> @@ -7717,23 +7717,53 @@ void kvm_arch_sync_events(struct kvm *kvm)
>> int __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, u32 size)
>> {
>> int i, r;
>> + u64 hva;
>> + struct kvm_memslots *slots = kvm_memslots(kvm);
>> + struct kvm_memory_slot *slot, old;
> | [...]
>> + slot = &slots->memslots[slots->id_to_index[id]];
>
> This seems better written as
>
> slot = id_to_memslot(slots, id);
Gah, I could not recall the right API! I'll fix it.
> (Made me remember that I want to refactor the memslot API ...)
>
> | [...]
>> + } else {
>> + if (!slot->npages)
>> + return 0;
>> +
>> + hva = 0;
>> + }
>> +
>> + old = *slot;
>
> (Assignment could be in the 'else' == !size branch, GCC would have fun.)
It would have fun _and_ warn, which is why it's not in the else branch. :)
Paolo
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