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Re: [PATCH 0/6] Add various undefined MMIO r/w functions
From: |
Paolo Bonzini |
Subject: |
Re: [PATCH 0/6] Add various undefined MMIO r/w functions |
Date: |
Wed, 17 Jun 2020 17:08:33 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 |
On 17/06/20 15:20, Philippe Mathieu-Daudé wrote:
> On 6/17/20 3:06 PM, Alex Williamson wrote:
>> On Wed, 17 Jun 2020 16:39:56 +1000
>> David Gibson <david@gibson.dropbear.id.au> wrote:
>>
>>> On Wed, Jun 17, 2020 at 11:09:27AM +0530, P J P wrote:
>>>> From: Prasad J Pandit <pjp@fedoraproject.org>
>>>>
>>>> Hello,
>>>>
>>>> This series adds various undefined MMIO read/write functions
>>>> to avoid potential guest crash via a NULL pointer dereference.
>>>
>>> Hrm. If this is such a common problem, maybe we should just add a
>>> NULL check in the common paths.
>>
>> +1, clearly the behavior is already expected. Thanks,
>
> 20 months ago Peter suggested:
>
> "assert that every MemoryRegionOps has pointers to callbacks
> in it, when it is registered in memory_region_init_io() and
> memory_region_init_rom_device_nomigrate()."
>
> https://www.mail-archive.com/qemu-devel@nongnu.org/msg573310.html
>
> Li Qiang refers to this post from Paolo:
>
>> static const MemoryRegionOps notdirty_mem_ops = {
>> + .read = notdirty_mem_read,
>> .write = notdirty_mem_write,
>> .valid.accepts = notdirty_mem_accepts,
>> .endianness = DEVICE_NATIVE_ENDIAN,
>
> "This cannot happen, since TLB_NOTDIRTY is only added
> to the addr_write member (see accel/tcg/cputlb.c)."
I'm now okay with asserting it, as long as notdirty_mem_read abort()s.
Paolo
- [PATCH 5/6] nvram: add nrf51_soc flash read method, (continued)