fix writing by using a virtual image instead of a physical thumbdrive, better document the hack in KeIrqDispatch

.gitignore

@@ -2,3 +2,4 @@ vc140.pdb
 bin/
 obj/
 qemu.log
+disk.vhd

build.bat

@@ -3,7 +3,12 @@ setlocal enabledelayedexpansion
 
 set ROOT=%~dp0.
 set SRC=%ROOT%\code
-set DEST=%NTLITE_DRIVE%
+set VHD=%~dp0disk.vhd
+
+if not exist "%VHD%" (
+    echo ERROR: disk.vhd not found. Run mkimage.bat first.
+    exit /b 1
+)
 
 if exist "obj" rd /s /q "obj"
 if exist "bin" rd /s /q "bin"
@@ -129,6 +134,26 @@ echo Linking video.exe...
 link %LFLAGS% /SUBSYSTEM:NATIVE /ENTRY:main ^
     /OUT:"bin\video.exe" /PDB:"bin\video.pdb" bin\win32.lib obj\libc.obj %SRC%\video\bink2w64.lib obj\video\*.obj || exit /b 1
 
+:: ---- Mount disk image ----
+echo Mounting disk.vhd as Z: ...
+set DPS=%TEMP%\ntlite_mnt_%RANDOM%.txt
+(
+    echo select vdisk file="%VHD%"
+    echo attach vdisk
+    echo select partition 1
+    echo assign letter=Z
+    echo exit
+) > "%DPS%"
+diskpart /s "%DPS%"
+del "%DPS%"
+
+if not exist "Z:\" (
+    echo ERROR: Could not mount disk.vhd as Z:
+    echo If Z: is already in use, change the letter in build.bat and mkimage.bat.
+    exit /b 1
+)
+set DEST=Z:
+
 :: ---- Copy to ESP layout ----
 echo Assembling ESP...
 mkdir "%DEST%\drivers" 2>nul
@@ -147,6 +172,18 @@ copy /y "bin\shell.exe"   "%DEST%\"
 copy /y "bin\video.exe"   "%DEST%\"
 copy /y "%SRC%\boot.ini"  "%DEST%\"
 copy /y "%SRC%\drivers\drivers.ini" "%DEST%\drivers\"
+if exist "%SRC%\video\bink2w64.dll" copy /y "%SRC%\video\bink2w64.dll" "%DEST%\"
+
+:: ---- Unmount disk image ----
+echo Unmounting disk.vhd...
+set DPS=%TEMP%\ntlite_umnt_%RANDOM%.txt
+(
+    echo select vdisk file="%VHD%"
+    echo detach vdisk
+    echo exit
+) > "%DPS%"
+diskpart /s "%DPS%"
+del "%DPS%"
 
 echo.
 echo Build complete.

code/kernel/ke_irq.c

@@ -18,7 +18,12 @@ __declspec(dllexport) void KeIrqRegister(uint8_t irq, void (*handler)(void)) {
 }
 
 void KeIrqDispatch(uint8_t irq) {
-    // eoi first, handler second because it doesn't work otherwise.
+    // KeIrqDispatch sends EOI after the handler returns, but the handler switched context before returning.
+    // The EOI call is still sitting on the idle thread's stack, waiting for that thread to be resumed.
+    // The LAPIC sees ISR[0x20] still set. Its rule is: don't deliver another interrupt at the same or lower priority until EOI is written.
+    // So the timer never fires again. The user process runs completely unpreempted until it calls SYS_EXIT_PROCESS, which calls KeYield, which cooperatively switches back
+    // and only then does the idle thread resume, KeIrqDispatch finally sends its EOI, and the timer starts firing again.
+    // To fix this we send EOI before calling the handler, not after.
     gHal->Intc.SendEoi();
     if (irq < MAX_IRQS && gIrqHandlers[irq])
         gIrqHandlers[irq]();

mkimage.bat

@@ -0,0 +1,37 @@
+@echo off
+setlocal
+set VHD=%~dp0disk.vhd
+
+echo === nt-lite: create disk image ===
+echo.
+
+if exist "%VHD%" (
+    echo Removing old disk.vhd...
+    del "%VHD%"
+)
+
+:: Write a diskpart script to a temp file (avoids pipe/echo escaping issues)
+set DPS=%TEMP%\ntlite_mkimg_%RANDOM%.txt
+(
+    echo create vdisk file="%VHD%" maximum=256 type=fixed
+    echo select vdisk file="%VHD%"
+    echo attach vdisk
+    echo create partition primary
+    echo format fs=fat32 label=NTLITE quick
+    echo detach vdisk
+    echo exit
+) > "%DPS%"
+
+echo Creating 256 MB FAT32 image via diskpart...
+diskpart /s "%DPS%"
+del "%DPS%"
+
+if exist "%VHD%" (
+    echo.
+    echo disk.vhd ready. Run build.bat to populate it.
+) else (
+    echo.
+    echo ERROR: disk.vhd was not created.
+    echo Make sure you are running as Administrator.
+    exit /b 1
+)

readme.md

@@ -26,11 +26,9 @@ It boots into a shell.
 
 ## how 2 build
 
-* open env variables
-* set `NTLITE_DRIVE` as your thumbdrive (ex. `G:`)
-* set `NTLITE_NTPATH` as your thumbdrive (ex. `\\.\PhysicalDrive7`)
-* open vs x64 build tools
+* open vs x64 build tools as admin
 * cd into this directory
+* `mkimage.bat`
 * `build.bat`
 * `run.bat`(ide)/`rund.bat`(ide, debug)/`runa.bat`(ahci)/`runad.bat`(ahci, debug)
 * enjoy

run.bat

@@ -1 +1 @@
-@start qemu-system-x86_64 -drive if=pflash,format=raw,readonly=on,file=OVMF\OVMF_CODE_4M.fd -drive if=pflash,format=raw,file=OVMF\OVMF_VARS_4M.fd -drive format=raw,file=%NTLITE_NTPATH% -serial stdio
+@start qemu-system-x86_64 -drive if=pflash,format=raw,readonly=on,file=OVMF\OVMF_CODE_4M.fd -drive if=pflash,format=raw,file=OVMF\OVMF_VARS_4M.fd -drive format=vpc,file=disk.vhd -serial stdio

runa.bat

@@ -1 +1 @@
-@start qemu-system-x86_64 -drive if=pflash,format=raw,readonly=on,file=OVMF\OVMF_CODE_4M.fd -drive if=pflash,format=raw,file=OVMF\OVMF_VARS_4M_d.fd -device ahci,id=ahci -drive format=raw,file=%NTLITE_NTPATH%,if=none,id=disk0 -device ide-hd,bus=ahci.0,drive=disk0 -serial stdio
+@start qemu-system-x86_64 -drive if=pflash,format=raw,readonly=on,file=OVMF\OVMF_CODE_4M.fd -drive if=pflash,format=raw,file=OVMF\OVMF_VARS_4M_d.fd -device ahci,id=ahci -drive format=vpc,file=disk.vhd,if=none,id=disk0 -device ide-hd,bus=ahci.0,drive=disk0 -serial stdio

runad.bat

@@ -1 +1 @@
-@start qemu-system-x86_64 -drive if=pflash,format=raw,readonly=on,file=OVMF\OVMF_CODE_4M.fd -drive if=pflash,format=raw,file=OVMF\OVMF_VARS_4M_d.fd -device ahci,id=ahci -drive format=raw,file=%NTLITE_NTPATH%,if=none,id=disk0 -device ide-hd,bus=ahci.0,drive=disk0 -m 4G -serial stdio -d in_asm,cpu_reset,int -D qemu.log -no-reboot -no-shutdown
+@start qemu-system-x86_64 -drive if=pflash,format=raw,readonly=on,file=OVMF\OVMF_CODE_4M.fd -drive if=pflash,format=raw,file=OVMF\OVMF_VARS_4M_d.fd -device ahci,id=ahci -drive format=vpc,file=disk.vhd,if=none,id=disk0 -device ide-hd,bus=ahci.0,drive=disk0 -m 4G -serial stdio -d in_asm,cpu_reset,int -D qemu.log -no-reboot -no-shutdown

rund.bat

@@ -1 +1 @@
-@start qemu-system-x86_64 -drive if=pflash,format=raw,readonly=on,file=OVMF\OVMF_CODE_4M.fd -drive if=pflash,format=raw,file=OVMF\OVMF_VARS_4M.fd -drive format=raw,file=%NTLITE_NTPATH% -m 4G -serial stdio -d in_asm,cpu_reset,int -D qemu.log -no-reboot -no-shutdown
+@start qemu-system-x86_64 -drive if=pflash,format=raw,readonly=on,file=OVMF\OVMF_CODE_4M.fd -drive if=pflash,format=raw,file=OVMF\OVMF_VARS_4M.fd -drive format=vpc,file=disk.vhd -m 4G -serial stdio -d in_asm,cpu_reset,int -D qemu.log -no-reboot -no-shutdown