Re: [Qemu-devel] [PATCH] migration: check length directly to make sure the range is aligned

[Wei Yang <richardw.yang@linux.intel.com>]

On Fri, Jul 19, 2019 at 06:54:00PM +0100, Dr. David Alan Gilbert wrote:
>* Wei Yang (richardw.yang@linux.intel.com) wrote:
>> Since the start addr is already checked, to make sure the range is
>> aligned, checking the length is enough.
>> 
>> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
>> ---
>>  exec.c | 7 +++----
>>  1 file changed, 3 insertions(+), 4 deletions(-)
>> 
>> diff --git a/exec.c b/exec.c
>> index 50ea9c5aaa..8fa980baae 100644
>> --- a/exec.c
>> +++ b/exec.c
>> @@ -4067,10 +4067,9 @@ int ram_block_discard_range(RAMBlock *rb, uint64_t start, size_t length)
>>  
>>      if ((start + length) <= rb->used_length) {
>>          bool need_madvise, need_fallocate;
>> -        uint8_t *host_endaddr = host_startaddr + length;
>> -        if ((uintptr_t)host_endaddr & (rb->page_size - 1)) {
>> -            error_report("ram_block_discard_range: Unaligned end address: %p",
>> -                         host_endaddr);
>> +        if (length & (rb->page_size - 1)) {
>> +            error_report("ram_block_discard_range: Unaligned length: %lx",
>> +                         length);
>
>Yes, I *think* this is safe, we'll need to watch out for any warnings;
>David Gibson's balloon fix from February means that the balloon code
>should now warn in it's case.
>
>rth: Want to pick this up?
>
>Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>

Hi, David

Do you like this one?

>>              goto err;
>>          }
>>  
>> -- 
>> 2.17.1
>> 
>--
>Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

-- 
Wei Yang
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