Re: [PATCH 1/1] KVM: Fix kernel allocated memory slot

[Anthony Liguori <anthony@codemonkey.ws>]

Sheng Yang wrote:
> On Tuesday 11 November 2008 22:58:25 Hollis Blanchard wrote:
>   
>> On Tue, 2008-11-11 at 15:30 +0800, Sheng Yang wrote:
>>     
>>> Commit 7fd49de9773fdcb7b75e823b21c1c5dc1e218c14 "KVM: ensure that memslot
>>> userspace addresses are page-aligned" broke kernel space allocated memory
>>> slot, for the userspace_addr is invalid.
>>>
>>> Signed-off-by: Sheng Yang <sheng@linux.intel.com>
>>> ---
>>>  virt/kvm/kvm_main.c |    2 +-
>>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
>>> index 0a0a959..4727c08 100644
>>> --- a/virt/kvm/kvm_main.c
>>> +++ b/virt/kvm/kvm_main.c
>>> @@ -715,7 +715,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
>>>  		goto out;
>>>  	if (mem->guest_phys_addr & (PAGE_SIZE - 1))
>>>  		goto out;
>>> -	if (mem->userspace_addr & (PAGE_SIZE - 1))
>>> +	if (user_alloc && (mem->userspace_addr & (PAGE_SIZE - 1)))
>>>  		goto out;
>>>  	if (mem->slot >= KVM_MEMORY_SLOTS + KVM_PRIVATE_MEM_SLOTS)
>>>  		goto out;
>>>       
>> Wow, I didn't realize we still had kernel-allocated guest memory. Why is
>> that?
>>
>> Anyways, the above patch seems fine to me.
>> Acked-by: Hollis Blanchard <hollisb@us.ibm.com>
>>     
>
> it's for VMX EPT and APIC access page, as well as TSS pages. We are planning 
> to change that in the future, but I think it's a quick fix for now.
>   

It's also there to support older userspaces that still rely on the 
kernel allocating guest memory.  This is only applicable to x86 though.

Regards,

Anthony Liguori

> Thanks.
>
>