Commit d3561b7f authored by Rusty Russell's avatar Rusty Russell Committed by Andi Kleen
Browse files

[PATCH] paravirt: header and stubs for paravirtualisation 



Create a paravirt.h header for all the critical operations which need to be
replaced with hypervisor calls, and include that instead of defining native
operations, when CONFIG_PARAVIRT.

This patch does the dumbest possible replacement of paravirtualized
instructions: calls through a "paravirt_ops" structure.  Currently these are
function implementations of native hardware: hypervisors will override the ops
structure with their own variants.

All the pv-ops functions are declared "fastcall" so that a specific
register-based ABI is used, to make inlining assember easier.

And:

+From: Andy Whitcroft <apw@shadowen.org>

The paravirt ops introduce a 'weak' attribute onto memory_setup().
Code ordering leads to the following warnings on x86:

    arch/i386/kernel/setup.c:651: warning: weak declaration of
                `memory_setup' after first use results in unspecified behavior

Move memory_setup() to avoid this.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: default avatarChris Wright <chrisw@sous-sol.org>
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Zachary Amsden <zach@vmware.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarAndy Whitcroft <apw@shadowen.org>
parent db91b882

arch/i386/Kconfig

+11 −0
Original line number Diff line number Diff line
@@ -182,6 +182,17 @@ config X86_ES7000 


endchoice



config PARAVIRT

	bool "Paravirtualization support (EXPERIMENTAL)"

	depends on EXPERIMENTAL

	help

	  Paravirtualization is a way of running multiple instances of

	  Linux on the same machine, under a hypervisor.  This option

	  changes the kernel so it can modify itself when it is run

	  under a hypervisor, improving performance significantly.

	  However, when run without a hypervisor the kernel is

	  theoretically slower.  If in doubt, say N.



config ACPI_SRAT

	bool

	default y

arch/i386/boot/compressed/misc.c

+1 −0
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ 
 * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996

 */



#undef CONFIG_PARAVIRT

#include <linux/linkage.h>

#include <linux/vmalloc.h>

#include <linux/screen_info.h>

arch/i386/kernel/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -39,6 +39,7 @@ obj-$(CONFIG_VM86) += vm86.o 
obj-$(CONFIG_EARLY_PRINTK)	+= early_printk.o

obj-$(CONFIG_HPET_TIMER) 	+= hpet.o

obj-$(CONFIG_K8_NB)		+= k8.o

obj-$(CONFIG_PARAVIRT)		+= paravirt.o



EXTRA_AFLAGS   := -traditional

arch/i386/kernel/asm-offsets.c

+10 −0
Original line number Diff line number Diff line
@@ -101,4 +101,14 @@ void foo(void) 
	BLANK();

 	OFFSET(PDA_cpu, i386_pda, cpu_number);

	OFFSET(PDA_pcurrent, i386_pda, pcurrent);



#ifdef CONFIG_PARAVIRT

	BLANK();

	OFFSET(PARAVIRT_enabled, paravirt_ops, paravirt_enabled);

	OFFSET(PARAVIRT_irq_disable, paravirt_ops, irq_disable);

	OFFSET(PARAVIRT_irq_enable, paravirt_ops, irq_enable);

	OFFSET(PARAVIRT_irq_enable_sysexit, paravirt_ops, irq_enable_sysexit);

	OFFSET(PARAVIRT_iret, paravirt_ops, iret);

	OFFSET(PARAVIRT_read_cr0, paravirt_ops, read_cr0);

#endif

}

arch/i386/kernel/entry.S

+27 −7
Original line number Diff line number Diff line
@@ -62,13 +62,6 @@ DF_MASK = 0x00000400 
NT_MASK		= 0x00004000

VM_MASK		= 0x00020000



/* These are replaces for paravirtualization */

#define DISABLE_INTERRUPTS		cli

#define ENABLE_INTERRUPTS		sti

#define ENABLE_INTERRUPTS_SYSEXIT	sti; sysexit

#define INTERRUPT_RETURN		iret

#define GET_CR0_INTO_EAX		movl %cr0, %eax



#ifdef CONFIG_PREEMPT

#define preempt_stop		DISABLE_INTERRUPTS; TRACE_IRQS_OFF

#else
@@ -416,6 +409,20 @@ ldt_ss: 
	jnz restore_nocheck

	testl $0x00400000, %eax		# returning to 32bit stack?

	jnz restore_nocheck		# allright, normal return



#ifdef CONFIG_PARAVIRT

	/*

	 * The kernel can't run on a non-flat stack if paravirt mode

	 * is active.  Rather than try to fixup the high bits of

	 * ESP, bypass this code entirely.  This may break DOSemu

	 * and/or Wine support in a paravirt VM, although the option

	 * is still available to implement the setting of the high

	 * 16-bits in the INTERRUPT_RETURN paravirt-op.

	 */

	cmpl $0, paravirt_ops+PARAVIRT_enabled

	jne restore_nocheck

#endif



	/* If returning to userspace with 16bit stack,

	 * try to fix the higher word of ESP, as the CPU

	 * won't restore it.
@@ -833,6 +840,19 @@ nmi_espfix_stack: 
.previous

KPROBE_END(nmi)



#ifdef CONFIG_PARAVIRT

ENTRY(native_iret)

1:	iret

.section __ex_table,"a"

	.align 4

	.long 1b,iret_exc

.previous



ENTRY(native_irq_enable_sysexit)

	sti

	sysexit

#endif



KPROBE_ENTRY(int3)

	RING0_INT_FRAME

	pushl $-1			# mark this as an int

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