Re: Simple patches for Linux as a guest OS in a plex86 VM (please consider)

[Kevin Lawton <kevinlawton2001@yahoo.com>]

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--- Kai Germaschewski <kai@tp1.ruhr-uni-bochum.de> wrote:

> Three minor points:

OK, done.  Here's my #3 submission.  Some great
feedback from you guys.  Mods are down to:

  o Documentation/x86-hal.txt      # added file
  o include/asm-i386/if.h          # added file (only used for VM)
  o arch/i386/Kconfig              # added one menu entry
  o arch/i386/Makefile             # added one ifdef..endif
  o arch/i386/boot/Makefile        # added one ifdef..endif

-Kevin

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diff -urN linux-2.5.59/Documentation/x86-hal.txt linux-2.5.59-hal/Documentation/x86-hal.txt
--- linux-2.5.59/Documentation/x86-hal.txt	Wed Dec 31 19:00:00 1969
+++ linux-2.5.59-hal/Documentation/x86-hal.txt	Thu Jan 23 01:07:23 2003
@@ -0,0 +1,114 @@
+x86 Hardware Abstraction Layer
+==============================
+
+Maintained by Kevin P. Lawton <kevinlawton2001@yahoo.com>
+Last updated: Wed Jan 22 17:05:05 EST 2003
+
+The goal of the x86 hardware abstraction layer is to provide
+a way to run the mainstream x86 Linux kernel as a guest OS, in
+a lightweight Virtual Machine (VM), provided by a new cut-down
+plex86 port.  For reference, see the section on plex86.
+
+The idea being, to have the ability to configure/compile x86 Linux
+"out-of-the-box", disabling lots of unnecessary host-oriented
+hardware support, and running it unpatched inside a special
+VM container.
+
+Because the VM understands that a VM'able guest OS is running,
+_many_ of the heavy x86 VM techniques are unnessary, and only
+the core set of IO functionality needs to be emulated; things
+like the interrupt controller, timers, straight text-mode
+VGA frame buffer, and other things which are very lightweight
+to emulate.  References to these devices can be easily monitored
+by a VM monitor, without modification to the Linux kernel.
+
+The functionality of heavy IO devices like disk/network, are
+best handled by efficient loadable kernel modules designed for
+Linux as a guest.  These modules can communicate a hardware
+abstraction layer protocol to the host OS outside the VM
+to handle the IO workload independently by the host OS,
+which is likely Linux (of course!).
+
+
+Why a Linux VM?
+===============
+
+  o Ability to have multiple Linux installations on one machine
+    at your disposal, with various software configuations.
+    This is great for developers, and call-in support centers
+    who need to have a matrix of OS/application versions
+    available.
+
+  o Security.  There are tons of applications here.  Firewalling
+    of certain applications, honey-pots, ...  I'll let the
+    security guys fill in this category.
+
+  o Provisioning of server resources.  Having the ability to
+    consolidate servers to optimize the use of each CPU.  And
+    to dynamically spin up servers on-demand.  Lots of
+    consoliation and load-balancing plays here.
+
+  o Ability to log into a specific/personal VM "context"
+    from across the Internet, but to have the VM centrally
+    located (and maintained) on servers.  The "context"
+    is the particular Linux install with all of the
+    user-specific files.
+
+
+What is plex86?
+===============
+
+Plex86 is an x86 virtual machine project.  Though it's a separate
+entity, it is currently a subdirectory of "bochs", an x86 PC
+emulation project which can be found on
+
+  http://bochs.sourceforge.net/
+
+Originally, the goals of plex86 were to run any guest OS
+inside the VM, which required some heavy trickery.  I
+completely gutted plex86, and now it is an incredibly
+small and lightweight x86 VM, meant to run code which
+is "VM friendly".  Or in other words, if you don't need to
+run non-Linux, you don't need 99% of the VM baggage.
+
+Plex86 is not ready yet for running Linux as a guest, but I do
+have it working in tandem with bochs to run Linux user-level
+code inside the VM.
+
+
+How much does it cost?
+======================
+
+Nothing, it's Open Source.  Linux is obviously a GPL'd program.
+Plex86 is an LGPL'd kernel module.
+
+
+What kind of modifications to the Linux kernel are needed?
+==========================================================
+
+The ideal answer would be none.  The goal is to run the
+actual x86 codebase, with the aim for this to be usable in
+enterprise-level settings.  Thus, it's much more appealing
+not to have modifications, but to leverage all the
+testing that the main codebase goes through.
+
+So far, there are just a couple x86 instructions which
+can be easily macro'ized to change their behaviour, relating
+to manipulation of the interrupt flag.  This is due to
+a deficiency in the handling of code running with Protected
+mode Virtual Interrupts (PVI).  Thus far, the code impact
+is one extra header file, and a few lines to conditionally
+include it!
+
+I am _really_ hoping these small mods make it into the main
+kernel base before Linux 2.6.0.  I believe there will be
+commercial thrust behind running Linux VMs, and would like
+to see the ability to compile kernel source included with
+the major Linux distros, as-is with no extra patches.
+
+For kernel modules which are developed to facilitate a
+Linux VM communicating HAL protocol to the host Linux,
+I have no religion.  They can be maintained wherever makes
+sense.
+
+-Kevin
diff -urN linux-2.5.59/arch/i386/Kconfig linux-2.5.59-hal/arch/i386/Kconfig
--- linux-2.5.59/arch/i386/Kconfig	Wed Jan 22 12:25:59 2003
+++ linux-2.5.59-hal/arch/i386/Kconfig	Wed Jan 22 23:41:11 2003
@@ -1661,3 +1661,20 @@
 	bool
 	depends on SMP
 	default y
+
+menu "Hardware Abstraction Layer"
+
+config X86_HAL
+	bool "Compile for HAL (experimental)"
+	depends on !HIGHMEM && !SMP && !M486 && !M386 && !X86_UP_APIC && !X86_UP_IOAPIC
+	help
+    Experimental: Say Y here _only_ if you are compiling Linux to run inside
+    an experimental Hardware Abstraction Layer.  This is only useful
+    for running Linux as a guest OS in a special virtual machine.
+    Say N here unless you absolutely know what this is for.  This
+    will break Linux running on a real machine for sure.  This option
+    has the following configuration constraints: Pentium or higher,
+    uniprocessor mode, no apic support.  For more info see
+    <file:Documentation/x86-hal.txt>.
+
+endmenu
diff -urN linux-2.5.59/arch/i386/Makefile linux-2.5.59-hal/arch/i386/Makefile
--- linux-2.5.59/arch/i386/Makefile	Wed Jan 22 12:25:59 2003
+++ linux-2.5.59-hal/arch/i386/Makefile	Thu Jan 23 01:14:14 2003
@@ -90,6 +90,19 @@
 CFLAGS += $(mflags-y)
 AFLAGS += $(mflags-y)
 
+ifdef CONFIG_X86_HAL
+# On x86, if compiling for the Hardware Abstraction Layer
+# (running Linux as a guest OS in a Virtual Machine),
+# we need to insert some asm macros which redefine
+# the behaviour of instructions which modify the
+# interrupt flag.  You are probably not configuring for
+# this mode.  For more info, read 'Documentation/x86-hal.txt'.
+# This needs to be the first include any module sees.
+CFLAGS          += -include include/asm/if.h
+AFLAGS          += -include include/asm/if.h
+AFLAGS_vmlinux.lds.o += -DNO_X86_HAL_INCLUDES
+endif
+
 boot := arch/i386/boot
 
 .PHONY: zImage bzImage compressed zlilo bzlilo zdisk bzdisk install \
diff -urN linux-2.5.59/arch/i386/boot/Makefile linux-2.5.59-hal/arch/i386/boot/Makefile
--- linux-2.5.59/arch/i386/boot/Makefile	Tue Jan 14 00:58:35 2003
+++ linux-2.5.59-hal/arch/i386/boot/Makefile	Wed Jan 22 22:52:40 2003
@@ -32,6 +32,10 @@
 
 host-progs	:= tools/build
 
+ifdef CONFIG_X86_HAL
+AFLAGS += -DNO_X86_HAL_INCLUDES
+endif
+
 # ---------------------------------------------------------------------------
 
 $(obj)/zImage:  IMAGE_OFFSET := 0x1000
diff -urN linux-2.5.59/include/asm-i386/if.h linux-2.5.59-hal/include/asm-i386/if.h
--- linux-2.5.59/include/asm-i386/if.h	Wed Dec 31 19:00:00 1969
+++ linux-2.5.59-hal/include/asm-i386/if.h	Wed Jan 22 22:35:02 2003
@@ -0,0 +1,157 @@
+#ifndef NO_X86_HAL_INCLUDES
+/*
+ *	Routines to manipulate the interrupt flag (EFLAGS.IF).  Abstracting
+ *	them, makes it easier to compile for a hardware abstraction layer (HAL).
+ *
+ *	(c) 2003 Kevin P. Lawton <kevinlawton2001@yahoo.com>
+ */
+
+#ifndef _LINUX_ASM_IF_H_
+#define _LINUX_ASM_IF_H_
+
+
+/* NOTE: This file is directly included via the "-include include/asm/if.h"
+ * option conditionally added to the compiler flags by the top Makefile when
+ * CONFIG_X86_HAL is defined.  None of the header files have been included
+ * at this point.
+ */
+
+/* For a HAL (Hardware Abstraction Layer) compile, the kernel is executed
+ * at PL=3 using PVI (Protected mode Virtual Interrupts), which are the
+ * analog to VME for v86 code.  For some reason, The Creators stopped short of
+ * implementing proper IF handling for PUSHF/POPF for PVI, but STI/CLI are
+ * fine.  So we have to complete the PVI semantics using the following
+ * sequences.
+ */
+
+/* Shield your eyes.  These macros make it possible to use the same
+ * code for asm or C inline asm, with all the quoting, comma, and
+ * newline issues.  Q1 is for lines with no commas, and Q2 is for lines
+ * with one comma.
+ */
+#ifdef __ASSEMBLY__
+#define Q1(s0)     s0
+#define Q2(s0, s1) s0, s1
+#else
+#define Q1(s0)     #s0 "\n\t"
+#define Q2(s0, s1) #s0 "," #s1 "\n\t"
+#endif
+
+
+#ifndef __ASSEMBLY__
+__asm__ (
+#endif
+
+  Q1(.macro  cli)
+  Q1(.byte 0xfa)     /* cli (native instruction works fine in PVI) */
+  Q1(.endm)
+
+  Q1(.macro  sti)
+  Q1(.byte 0xfb)     /* sti (native instruction works fine in PVI) */
+  Q1(.endm)
+
+#ifndef __ASSEMBLY__
+  );
+#endif
+
+
+
+/* PUSHFL:
+ * When execution is monitored using PVI (Protected mode Virtual Interrupts),
+ * we have to complete the PVI semantics of the PUSHFL instruction, as
+ * per behaviour of VME.
+ *
+ *                        b19           b9
+ * CPU   image of eflags: VIF           IF
+ *                         |
+ *                         +------------+
+ *                                      |
+ *                                      v
+ * Stack image of eflags: VIF           IF
+ *
+ * Notes: VIF on the stack image could be cleared, if it matters.
+ */
+
+#ifndef __ASSEMBLY__
+__asm__ (
+#endif
+
+  Q1(  .macro pushfl)
+  Q1(  .byte 0x9c)                /* (pushfl) Final eflags stack image. */
+  Q1(  .byte 0x9c)                /* (pushfl) For restoring arith flags. */
+  Q2(  testl $(1<<19), 4(%esp))   /* Was VIF bit set? */
+  Q1(  jz 69001f)
+  Q2(  orl   $(1<<9), 4(%esp))    /* Yes: set stack image of IF. */
+  Q1(  jmp 69002f)
+  Q1(69001:)                      /* Use the zip of Lyon France :^} */
+  Q2(  andl  $~(1<<9), 4(%esp))   /* No: clear stack image of IF. */
+  Q1(69002:)
+  Q1(  .byte 0x9d)                /* (popfl) Restore arithmetic flags. */
+  Q1(  .endm)
+
+  /* The user may use pushf with an implicit size.  Just expand that
+   * to the previous macro.
+   */
+  Q1(.macro pushf)
+  Q1(pushfl)
+  Q1(.endm)
+
+#ifndef __ASSEMBLY__
+  );
+#endif
+
+
+
+/* POPFL:
+ * When execution is monitored using PVI (Protected mode Virtual Interrupts),
+ * we have to complete the PVI semantics of the POPFL instruction, as
+ * per behaviour of VME.
+ *
+ *                        b19           b9
+ * Stack image of eflags: VIF           IF
+ *                                      |
+ *                         +------------+
+ *                         |
+ *                         v
+ * CPU   image of eflags: VIF           IF
+ *
+ * Notes: IF of the eflags register retains its previous value, which
+ *   should be 1 (when monitored down to PL3, the processor ignores this
+ *   bit in a POPF).
+ */
+
+#ifndef __ASSEMBLY__
+__asm__ (
+#endif
+
+  Q1(  .macro popfl)
+  Q2(  testl $(1<<9), 0(%esp))    /* Is IF set on stack image? */
+  Q1(  jz 69003f)
+  Q1(  .byte 0x9d)                /* (popfl) Yes: restore from stack and */
+  Q1(  sti)                       /* force VIF=1. */
+  Q1(  jmp 69004f)
+  Q1(69003:)
+  Q1(  .byte 0x9d)                /* (popfl) No: restore from stack and */
+  Q1(  cli)                       /* force VIF=0. */
+  Q1(69004:)
+  Q1(  .endm)
+
+  /* The user may use popf with an implicit size.  Just expand that
+   * to the previous macro.
+   */
+  Q1(.macro popf)
+  Q1(popfl)
+  Q1(.endm)
+
+#ifndef __ASSEMBLY__
+  );
+#endif
+
+/* Get rid of quoting macros - good housekeeping. */
+#undef Q1
+#undef Q2
+
+
+#endif  /* _LINUX_ASM_IF_H_ */
+
+#endif  /*  NO_X86_HAL_INCLUDES */