[Qemu-devel] Re: [PATCH] kvm: Fix overlapping check for memory slots

[Jan Kiszka <jan.kiszka@web.de>]

[-- Attachment #1: Type: text/plain, Size: 1377 bytes --]

Sheng Yang wrote:
> On Saturday 11 April 2009 17:48:04 Jan Kiszka wrote:
>> This nice little buglet complicates a smarter slot management in qemu
>> user space just "slightly". Sigh...
>>
>> -------->
>>
>> When checking for overlapping slots on registration of a new one, kvm
>> currently also considers zero-length (ie. deleted) slots and rejects
>> requests incorrectly. This finally denies user space from joining slots.
>> Fix the check by skipping deleted slots.
>>
>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.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 363af32..18f06d2 100644
>> --- a/virt/kvm/kvm_main.c
>> +++ b/virt/kvm/kvm_main.c
>> @@ -1117,7 +1117,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
>>  	for (i = 0; i < KVM_MEMORY_SLOTS; ++i) {
>>  		struct kvm_memory_slot *s = &kvm->memslots[i];
>>
>> -		if (s == memslot)
>> +		if (s == memslot || !s->npages)
>>  			continue;
>>  		if (!((base_gfn + npages <= s->base_gfn) ||
>>  		      (base_gfn >= s->base_gfn + s->npages)))
> 
> Is it necessary to preserve a valid base_gfn/flags/etc for a zeroed slot? 
> Seems kvm_free_physmem_slot didn't clean them.

It is not necessary as long as we ignore such slots (as this patch does).

Jan


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 257 bytes --]