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Re: [RFC PATCH 0/5] ARM: reduce the memory consumed when mapping UEFI fl
Re: [RFC PATCH 0/5] ARM: reduce the memory consumed when mapping UEFI flash images
Thu, 19 Nov 2020 07:09:14 +0100
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On 11/16/20 2:48 PM, Markus Armbruster wrote:
> Philippe Mathieu-Daudé <firstname.lastname@example.org> writes:
>> Hi David,
>> On 11/16/20 11:42 AM, David Edmondson wrote:
>>> Currently ARM UEFI images are typically built as 2MB/768kB flash
>>> images for code and variables respectively. These images are both then
>>> padded out to 64MB before being loaded by QEMU.
>>> Because the images are 64MB each, QEMU allocates 128MB of memory to
>>> read them, and then proceeds to read all 128MB from disk (dirtying the
>>> memory). Of this 128MB less than 3MB is useful - the rest is zero
>> 2 years ago I commented the same problem, and suggested to access the
>> underlying storage by "block", as this is a "block storage".
>> Back then the response was "do not try to fix something that works".
>> This is why we choose the big hammer "do not accept image size not
>> matching device size" way.
>> While your series seems to help, it only postpone the same
>> implementation problem. If what you want is use the least memory
>> required, I still believe accessing the device by block is the
>> best approach.
> "Do not try to fix something that works" is hard to disagree with.
> However, at least some users seem to disagree with "this works". Enough
> to overcome the resistance to change?
Yeah, at least 3 big users so far:
Then Huawei tried the MicroVM approach:
I simply wanted to save David time by remembering this other approach,
since Peter already commented on David's one (see Huawei link).
- Re: [RFC PATCH 1/5] hw/block: blk_check_size_and_read_all should report backend name, (continued)
- [RFC PATCH 4/5] hw/arm: Flash image mapping follows image size, David Edmondson, 2020/11/16
- [RFC PATCH 5/5] hw/arm: Only minimise flash size on older machines, David Edmondson, 2020/11/16
- [RFC PATCH 3/5] hw/arm: Convert assertions about flash image size to error_report, David Edmondson, 2020/11/16
- [RFC PATCH 2/5] hw/block: Flash images can be smaller than the device, David Edmondson, 2020/11/16
- Re: [RFC PATCH 0/5] ARM: reduce the memory consumed when mapping UEFI flash images, Philippe Mathieu-Daudé, 2020/11/16