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Re: [Qemu-devel] [PATCH 3/3] memory-device: break the loop if tmp exceed
From: |
Wei Yang |
Subject: |
Re: [Qemu-devel] [PATCH 3/3] memory-device: break the loop if tmp exceed the hinted range |
Date: |
Mon, 29 Jul 2019 16:30:19 +0800 |
User-agent: |
Mutt/1.9.4 (2018-02-28) |
On Mon, Jul 29, 2019 at 09:49:37AM +0200, David Hildenbrand wrote:
>On 28.07.19 15:13, Wei Yang wrote:
>> The memory-device list built by memory_device_build_list is ordered by
>> its address, this means if the tmp range exceed the hinted range, all
>> the following range will not overlap with it.
>>
>> Signed-off-by: Wei Yang <address@hidden>
>> ---
>> hw/mem/memory-device.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/hw/mem/memory-device.c b/hw/mem/memory-device.c
>> index 413b514586..aea47ab3e8 100644
>> --- a/hw/mem/memory-device.c
>> +++ b/hw/mem/memory-device.c
>> @@ -180,7 +180,7 @@ static uint64_t memory_device_get_free_addr(MachineState
>> *ms,
>> range_make_empty(&new);
>> break;
>> }
>> - } else if (!hint) {
>> + } else if (!hint || range_lob(&tmp) > range_upb(&new)) {
>> break;
>> }
>> }
>>
>
>Lower bound is inclusive, upper bound is exclusive. Shouldn't this be
>
>range_lob(&tmp) >= range_upb(&new)
>
Per my understanding, a range with start = 0, size = 0x10000, is represented
[0, 0xffff]
So if I have another range [0xffff, 0x1ffff], they seems to overlap. The range
[0x10000, 0x1ffff] doesn't overlap with [0, 0xffff].
My original comparison looks right. Do I miss some point?
>Also, I wonder if patch #2 is now really needed?
>
Hmm... I think you are right.
I am afraid without Patch #2, the condition check is not that intuitive. Would
this bring some confusion for audience and maintenance?
I am not sure the percentage of occurrence when hint is provided, while the
generated code for check NULL is less than compare two values.
>--
>
>Thanks,
>
>David / dhildenb
--
Wei Yang
Help you, Help me
- Re: [Qemu-devel] [PATCH 2/3] memory-device: break the loop if no hint is provided, (continued)