Re: [Qemu-devel] [PATCH] configure: Support system emulation with large memory on w32 hosts

[Alexey Kardashevskiy]

On 20/07/12 16:05, Alexey Kardashevskiy wrote:
> On 20/07/12 15:37, Alexey Kardashevskiy wrote:
>> On 20/07/12 15:23, Stefan Weil wrote:
>>> Am 20.07.2012 05:53, schrieb Alexey Kardashevskiy:
>>>> On 19/07/12 02:37, Stefan Weil wrote:
>>>>> 32-bit applications on Windows normally only get virtual memory in
>>>>> the lower 2 GiB address space.
>>>>>
>>>>> Because of memory fragmentation, VirtualAlloc() usually won't get 1 GiB
>>>>> of contiguous virtual memory in that address space. Therefore running
>>>>> system emulations with 1 GiB or more RAM will abort with a failure.
>>>>>
>>>>> The linker flag --large-address-aware allows addresses in the upper 2 GiB.
>>>>> With this flag, it is possible to run emulated machines with up to
>>>>> 2047 MiB RAM.
>>>>>
>>>>> Signed-off-by: Stefan Weil <address@hidden>
>>>>> ---
>>>>>
>>>>> I tested the executables with large address awareness on a 64 bit Windows
>>>>> (works) and with Wine on Debian 32 bit Linux (no longer aborts, but hangs
>>>>> when 1024 or more MiB are requested).
>>>>>
>>>>> Maybe the support for large addresses is broken in my Wine version.
>>>>> Please report any different test results.
>>>>
>>>> I tried with native WindowsXP, the patch did not help.
>>>>
>>>> QEMU was compiled with the new parameter:
>>>>
>>>> Install prefix    c:/Program Files/QEMU
>>>> BIOS directory    c:/Program Files/QEMU
>>>> binary directory  c:/Program Files/QEMU
>>>> library directory c:/Program Files/QEMU/lib
>>>> include directory c:/Program Files/QEMU/include
>>>> config directory  c:/Program Files/QEMU
>>>> Source path       /home/aik/testken/qemu
>>>> C compiler        i686-pc-mingw32-gcc
>>>> Host C compiler   gcc
>>>> CFLAGS            -O2 -D_FORTIFY_SOURCE=2 -g
>>>> QEMU_CFLAGS       -m32 -D__USE_MINGW_ANSI_STDIO=1 -DWIN32_LEAN_AND_MEAN
>>>> -DWINVER=0x501 -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE
>>>> -Wstrict-prototypes -Wredundant-decls -Wall -Wundef -Wwrite-strings
>>>> -Wmissing-prototypes -fno-strict-aliasing  -fstack-protector-all
>>>> -Wendif-labels -Wmissing-include-dirs -Wempty-body -Wnested-externs
>>>> -Wformat-security -Wformat-y2k -Winit-self -Wignored-qualifiers
>>>> -Wold-style-declaration -Wold-style-definition -Wtype-limits
>>>> LDFLAGS           -Wl,--nxcompat -Wl,--no-seh -Wl,--large-address-aware
>>>> -Wl,--dynamicbase -Wl,--warn-common -m32 -static -g
>>>> make              make
>>>> install           install
>>>> python            python
>>>> smbd              /usr/sbin/smbd
>>>> host CPU          i386
>>>> host big endian   no
>>>> target list       ppc64-softmmu
>>>> [...]
>>>>
>>>>
>>>>
>>>> qemu/ppc64-softmmu/qemu-system-ppc64 -M pseries -m 1024 -nographic -L
>>>> qemu/pc-bios/ -net none -append console=hvc0 -initrd ./1.cpio -kernel
>>>> ./guest.vmlinux.n -net nic,model=virtio -net user,hostfwd=tcp::5555-:22
>>>> -drive file=test-virtio-blk.img,if=virtio,index=0,media=disk,cache=unsafe
>>>> ***qemu_memalign 200 (512) size 800 (2048)
>>>> Warning: Disabling some instructions which are not emulated by TCG (0x0, 
>>>> 0x6)
>>>> ***qemu_vmalloc 40000000 (1073741824)
>>>> Failed to allocate memory: 8
>>>>
>>>> This application has requested the Runtime to terminate it in an unusual 
>>>> way.
>>>> Please contact the application's support team for more information.
>>>>
>>>>
>>>> The lines with *** are mine printf("%s %x(%u)", __func__, etc).
>>>>
>>>> It still works with "-m 1023".
>>>
>>> Do you have enough RAM? Even with 64 bit Windows 7, I am
>>> limited to -m 7000 with 64 bit QEMU on a 8 GiB host.
>>> 32 bit QEMU runs there with up to 2047 MiB.
>>
>>
>> I put another VirtualAlloc(64MB) call in qemu_vmalloc(1023MB) to check if
>> it fails but it did not so it is possible to allocate 1087MB but in 2 pieces.
>>
>>
>>> On 32 bit Windows XP, I'd expect that you need 2 GiB (or better
>>> 3 GiB) of physical RAM in your host, and close all other
>>> programs before you try QEMU.
>>
>> How do other programs matter? It is virtual 2GB per process, no?
>> Ah, anyway, it has 2.994.340KB of physical RAM, swapping is enabled, the
>> task manager shows at least "2000000" in "Available", one cygwin shell is
>> running.
>> And QEMU can always alloc 1023MB (in one chunk) and never 1024MB (also in
>> one chunk). For me it looks like XP limitation but I could not find any
>> mention of it in MSDN.
>>
>>
>>> Maybe I can run a test with Windows XP during the weekend.
>>>
>>> By the way: the patch must be modified to work for 64 bit QEMU.
>>> MinGW-w64's ld shows the new parameter in its help, but does
>>> not support it for 64 bit executables.
>>
>>
>> Not sure if I understood :)
>> The compiler I use is "i686-pc-mingw32-gcc -m32", target is ppc64-softmmu.
>>
>>
> 
> Did a simple test inside QEMU, ran it twice:
> 
> run#1: first alloc 64MB, then 1023MB - failed.
> va(0x4000000) -> ptr=1d0d0000, last error = 0
> va(0x3FF00000) -> ptr=00000000, last error = 8
> 
> run#2: first alloc 1023MB, then 64MB - succeeded.
> va(0x3FF00000) -> ptr=1d0d0000, last error = 0
> va(0x4000000) -> ptr=5d130000, last error = 0
> 
> As we can see, there is 340000h gap between 2 chunks.
> 
> Have no idea what that means :) May be something is wrong with my machine,
> dunno.

Looked further, c:\windows\system32\sysctl32.dll is mapped there so there
is just no big chunk of RAM. But still there is some RAM, it is just
fragmented.




-- 
Alexey