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

[Alexey Kardashevskiy]

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.


-- 
Alexey