On Thu, Dec 18, 2008 at 11:41:24AM +0200, Avi Kivity wrote:
> Glauber Costa wrote:
>> record slot used in last lookup. For the common mmio case,
>> we'll usually access the same memory slot repeatedly.
>>
>
>> --- a/kvm-all.c
>> +++ b/kvm-all.c
>> @@ -75,16 +75,25 @@ static KVMSlot *kvm_alloc_slot(KVMState *s)
>> return NULL;
>> }
>> +static KVMSlot *last_slot = NULL;
>> +
>> static KVMSlot *kvm_lookup_slot(KVMState *s, target_phys_addr_t start_addr)
>> {
>> int i;
>> +
>> + if (last_slot && (start_addr >= last_slot->start_addr &&
>> + start_addr < (last_slot->start_addr + last_slot->memory_size)))
>> + return last_slot;
>> +
>> for (i = 0; i < ARRAY_SIZE(s->slots); i++) {
>> KVMSlot *mem = &s->slots[i];
>> if (start_addr >= mem->start_addr &&
>> - start_addr < (mem->start_addr + mem->memory_size))
>> + start_addr < (mem->start_addr + mem->memory_size)) {
>> + last_slot = mem;
>> return mem;
>> + }
>> }
>>
>
> This wasn't introduced by this patch, but the comparison is broken ion
> i386 hosts, where target_phys_addr_t is 32 bits wide. mem->start_addr +
> mem->memory_size can overflow (this in fact happens for the bios slot at
> 4G-128K)
AFAIK, the assumption is that kvm will always be qemu-system-x86_64, due to
migration issues. Then, _target_ phys_addr_t is always 64 bit wide.
If it's not the case, then this is really a problem.
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