[Qemu-devel] [PATCH] -win2k-hack performance+DMA support

[Qemu-devel] [PATCH] -win2k-hack performance+DMA support

[Leonardo E. Reiter]

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Attached is a patch which greatly speeds up disk writes when using 
-win2k-hack to install Windows 2000.  It only delays every 16th 
interrupt, which after rigorous testing is still enough to overcome the 
"Windows 2000 disk full" bug.  If you are really adventurous you can try 
it every 32nd time, but for me that caused problems during some 
installations, so I thought it was too aggressive.

This patch also adds -win2k-hack functionality to DMA writes, since DMA 
now works in the latest CVS QEMU.

Enjoy,

Leo Reiter

-- 
Leonardo E. Reiter
Vice President of Product Development, CTO

Win4Lin, Inc.
Virtual Computing from Desktop to Data Center
Main: +1 512 339 7979
Fax: +1 512 532 6501
http://www.win4lin.com

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Index: hw/ide.c
===================================================================
RCS file: /cvsroot/qemu/qemu/hw/ide.c,v
retrieving revision 1.39
diff -a -u -r1.39 ide.c
--- hw/ide.c	1 Feb 2006 22:20:12 -0000	1.39
+++ hw/ide.c	2 Feb 2006 01:48:25 -0000
@@ -336,6 +336,7 @@
     uint8_t *data_end;
     uint8_t io_buffer[MAX_MULT_SECTORS*512 + 4];
     QEMUTimer *sector_write_timer; /* only used for win2k instal hack */
+    uint32_t irq_count; /* counts IRQs when using win2k install hack */
 } IDEState;
 
 #define BM_STATUS_DMAING 0x01
@@ -712,7 +713,7 @@
     ide_set_sector(s, sector_num + n);
     
 #ifdef TARGET_I386
-    if (win2k_install_hack) {
+    if (win2k_install_hack && ((++s->irq_count % 16) == 0)) {
         /* It seems there is a bug in the Windows 2000 installer HDD
            IDE driver which fills the disk with empty logs when the
            IDE write IRQ comes too early. This hack tries to correct
@@ -750,7 +751,19 @@
             if (n == 0) {
                 /* end of transfer */
                 s->status = READY_STAT | SEEK_STAT;
-                ide_set_irq(s);
+#ifdef TARGET_I386
+                if (win2k_install_hack && ((++s->irq_count % 16) == 0)) {
+                    /* It seems there is a bug in the Windows 2000 installer 
+                       HDD IDE driver which fills the disk with empty logs 
+                       when the IDE write IRQ comes too early. This hack tries 
+                       to correct that at the expense of slower write 
+                       performances. Use this option _only_ to install Windows 
+                       2000. You must disable it for normal use. */
+                    qemu_mod_timer(s->sector_write_timer, 
+                            qemu_get_clock(vm_clock) + (ticks_per_sec / 1000));
+                } else 
+#endif
+                    ide_set_irq(s);
                 return 0;
             }
             if (n > MAX_MULT_SECTORS)

Re: [Qemu-devel] [PATCH] -win2k-hack performance+DMA support

[Brad Campbell]

Leonardo E. Reiter wrote:
> Attached is a patch which greatly speeds up disk writes when using 
> -win2k-hack to install Windows 2000.  It only delays every 16th 
> interrupt, which after rigorous testing is still enough to overcome the 
> "Windows 2000 disk full" bug.  If you are really adventurous you can try 
> it every 32nd time, but for me that caused problems during some 
> installations, so I thought it was too aggressive.
> 
> This patch also adds -win2k-hack functionality to DMA writes, since DMA 
> now works in the latest CVS QEMU.
> 

Using todays CVS, and kqemu in user mode only I tried to install Win2k-SP4 25 times all with disk 
full errors until I applied this patch.
It would appear the installer will use DMA mode if it's available and therefore the existing 
win2k-hack does not work.

Using this patch 5 out of 5 installs worked perfectly.

Thanks Leo :)

Regards,
Brad
-- 
"Human beings, who are almost unique in having the ability
to learn from the experience of others, are also remarkable
for their apparent disinclination to do so." -- Douglas Adams

Re: [Qemu-devel] [PATCH] -win2k-hack performance+DMA support

[Leonardo E. Reiter]

No problem... hopefully Fabrice will apply this patch to CVS soon. 
We've been testing/deploying this mechanism (every 16th interrupt) with 
Win4Lin Pro for a long time now with no disk full problems, so I can 
vouch that it's reliable (and quite fast compared to delaying on *every* 
interrupt).  As for the DMA reintroducing the problem, that's 
understandable since Fabrice didn't originally implement the 
win2k_install_hack check for the DMA callback in hw/ide.c.  It was a 
moot point since DMA didn't work with Windows 2000 anyway in QEMU CVS 
until very recently, but since it does now, it will cause problems 
unless it handles -win2k-hack as well.

- Leo Reiter

Brad Campbell wrote:
> Using todays CVS, and kqemu in user mode only I tried to install 
> Win2k-SP4 25 times all with disk full errors until I applied this patch.
> It would appear the installer will use DMA mode if it's available and 
> therefore the existing win2k-hack does not work.
> 
> Using this patch 5 out of 5 installs worked perfectly.
> 
> Thanks Leo :)
> 
> Regards,
> Brad

-- 
Leonardo E. Reiter
Vice President of Product Development, CTO

Win4Lin, Inc.
Virtual Computing from Desktop to Data Center
Main: +1 512 339 7979
Fax: +1 512 532 6501
http://www.win4lin.com

Re: [Qemu-devel] [PATCH] -win2k-hack performance+DMA support

[Troy Benjegerdes]

On Thu, Feb 09, 2006 at 06:03:53PM +0400, Brad Campbell wrote:
> Leonardo E. Reiter wrote:
> >Attached is a patch which greatly speeds up disk writes when using 
> >-win2k-hack to install Windows 2000.  It only delays every 16th 
> >interrupt, which after rigorous testing is still enough to overcome the 
> >"Windows 2000 disk full" bug.  If you are really adventurous you can try 
> >it every 32nd time, but for me that caused problems during some 
> >installations, so I thought it was too aggressive.
> >
> >This patch also adds -win2k-hack functionality to DMA writes, since DMA 
> >now works in the latest CVS QEMU.
> >
> 
> Using todays CVS, and kqemu in user mode only I tried to install Win2k-SP4 
> 25 times all with disk full errors until I applied this patch.
> It would appear the installer will use DMA mode if it's available and 
> therefore the existing win2k-hack does not work.
> 
> Using this patch 5 out of 5 installs worked perfectly.
> 
> Thanks Leo :)
> 
> Regards,
> Brad

with current CVS, I am unable to install win2k.. This patch appears to
be needed for win2k installs to work.

With this patch, I am able to install w2k with user-kqemu.