Re: [PATCH 0/4] KVM: Clean up and optimize __kvm_set_memory_region() - part1

[Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>]

On 01/17/2013 03:07 AM, Marcelo Tosatti wrote:
> On Fri, Jan 11, 2013 at 06:25:18PM +0900, Takuya Yoshikawa wrote:
>> Patches 1 to 3 are trivial.
>>
>> Patch 4 is the main cause of the increased lines, but I think the new
>> code makes it easier to understand why each condition in
>> __kvm_set_memory_region() is there.
>>
>> If you don't agree with patch 4, please consider taking the rest of the
>> series at this time.
>>
>> Takuya Yoshikawa (4):
>>   KVM: set_memory_region: Don't jump to out_free unnecessarily
>>   KVM: set_memory_region: Don't check for overlaps unless we create or move a slot
>>   KVM: set_memory_region: Remove unnecessary variable memslot
>>   KVM: set_memory_region: Identify the requested change explicitly
>>
>>  virt/kvm/kvm_main.c |   94 ++++++++++++++++++++++++++++++++-------------------
>>  1 files changed, 59 insertions(+), 35 deletions(-)
>>
>> -- 
>> 1.7.5.4
> 
> Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
> 
> BTW, while at it, its probably worthwhile to restrict flags
> modifications: change from flags = 0 to flags = read-only is 
> incomplete. Xiao, should it be allowed only during creation?

Will Readonly memory be used for VM-mem-sharing in the future?
I remember you mentioned about mem-sharing things before. ;)

Actually, It is safe on KVM MMU because all the gfns in the slot
can become readonly after calling __kvm_set_memory_region. It is
unsafe on IOMMU, what need to be fixed is unmapping gfns on IOMMU
when the flag is changed.