[SeaBIOS] 回复:回复：Re: 回复：Re: _about ZoneHigh occupying ram from last address of below 4G ram

I just notice sending mail fail report

----- 原始邮件 -----
发件人: penghao122
收件人: Kevin O'Connor
抄送人: seabios
主题: 回复：Re: 回复：Re: [SeaBIOS]_about ZoneHigh occupying ram from last address of below 4G ram
日期: 2015-4-18 00:28

my qemu command line:
../qemu-2.1.2/x86_64-softmmu/qemu-system-x86_64 -k en-us  -chardev stdio,id=seabios -device isa-debugcon,iobase=0x402,chardev=seabios -smp 4  -m 8192 -drive file=/home/win7-64.qcow2,format=qcow2 -enable-kvm

Just for linux OS ,I agree with you about "It's common to put reserved memory at the end of ram ". My win7-64 vm delay two hours before booting up successfully .During the two hours,the windows OS access from 0xc000_0000 to 0xfc00_0000 byte by byte .There is no pci devices in the address range.  KVM think address space that is not in E820 table is mmio,but in fact this address space range also contain address hole. these hole should not be accessed by OS normally. Now windows OS access the hole ,so kvm think the address space is mmio,and handle the access like mmio flow (repeated kvm_exit to qemu userspace ).That is very time-consuming,so the vm delay 2 hours. I modified the ZoneHigh address at the begining of  128MB,everything is OK.
The bootloader of windows os may be care about memory at the end of ram below 4GB.

I try to start the same win7-64bit vm in xen-4.1.0(using rombios).It's OK because the rombios keep 0x10000 - 0xc000_0000 as ram..

p.s some edition of  win7-64bit is easy to trigge
----- 原始邮件 -----
发件人：Kevin O'Connor 
收件人：[e-mail]
抄送人：seabios 
主题：Re: 回复：Re: [SeaBIOS]_about ZoneHigh occupying ram from last address of below 4G ram
日期：2015年04月16日 22点22分

On Thu, Apr 16, 2015 at 10:08:48PM +0800, [e-mail] wrote:
> I configure ram to 4GB,then the win7-64bit vm can boot successfully
> using unmodified seabios. And I find that the vm can boot up after
> about 2 hours when configuring ram to 8G using unmodfied seabios.

What is your qemu/kvm command line?
It works fine for me (with a win7 beta I have locally). I do see a
brief pause around the point where you show a 2 hour delay, but the
delay for me is only a few seconds.
This is the command I used:
../qemu/qemu-2.2.0/x86_64-softmmu/qemu-system-x86_64 -k en-us -snapshot -L test -chardev stdio,id=seabios -device isa-debugcon,iobase=0x402,chardev=seabios -m 8192 -hda win7beta.img -enable-kvm -vga cirrus -smp 2 -usb
I think your issue should be reported on the QEMU/KVM mailing lists.
It's common to put reserved memory at the end of ram - for example,
run "dmesg | grep e820" on a real machine and see what it reports.
So, this doesn't look like a seabios issue to me.
-Kevin
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