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Commit 42b3a4cb authored by Juergen Gross's avatar Juergen Gross Committed by Thomas Gleixner
Browse files

x86/xen: Support early interrupts in xen pv guests 



Add early interrupt handlers activated by idt_setup_early_handler() to
the handlers supported by Xen pv guests. This will allow for early
WARN() calls not crashing the guest.

Suggested-by: default avatarAndy Lutomirski <luto@kernel.org>
Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: xen-devel@lists.xenproject.org
Cc: boris.ostrovsky@oracle.com
Link: https://lkml.kernel.org/r/20171124084221.30172-1-jgross@suse.com
parent 9d0b6232

arch/x86/include/asm/segment.h

+12 −0
Original line number Diff line number Diff line
@@ -236,11 +236,23 @@ 
 */

#define EARLY_IDT_HANDLER_SIZE 9



/*

 * xen_early_idt_handler_array is for Xen pv guests: for each entry in

 * early_idt_handler_array it contains a prequel in the form of

 * pop %rcx; pop %r11; jmp early_idt_handler_array[i]; summing up to

 * max 8 bytes.

 */

#define XEN_EARLY_IDT_HANDLER_SIZE 8



#ifndef __ASSEMBLY__



extern const char early_idt_handler_array[NUM_EXCEPTION_VECTORS][EARLY_IDT_HANDLER_SIZE];

extern void early_ignore_irq(void);



#if defined(CONFIG_X86_64) && defined(CONFIG_XEN_PV)

extern const char xen_early_idt_handler_array[NUM_EXCEPTION_VECTORS][XEN_EARLY_IDT_HANDLER_SIZE];

#endif



/*

 * Load a segment. Fall back on loading the zero segment if something goes

 * wrong.  This variant assumes that loading zero fully clears the segment.

arch/x86/mm/extable.c

+3 −1
Original line number Diff line number Diff line 
#include <linux/extable.h>

#include <linux/uaccess.h>

#include <linux/sched/debug.h>

#include <xen/xen.h>



#include <asm/fpu/internal.h>

#include <asm/traps.h>
@@ -212,8 +213,9 @@ void __init early_fixup_exception(struct pt_regs *regs, int trapnr) 
	 * Old CPUs leave the high bits of CS on the stack

	 * undefined.  I'm not sure which CPUs do this, but at least

	 * the 486 DX works this way.

	 * Xen pv domains are not using the default __KERNEL_CS.

	 */

	if (regs->cs != __KERNEL_CS)

	if (!xen_pv_domain() && regs->cs != __KERNEL_CS)

		goto fail;



	/*

arch/x86/xen/enlighten_pv.c

+24 −13
Original line number Diff line number Diff line
@@ -622,7 +622,7 @@ static struct trap_array_entry trap_array[] = { 
	{ simd_coprocessor_error,      xen_simd_coprocessor_error,      false },

};



static bool get_trap_addr(void **addr, unsigned int ist)

static bool __ref get_trap_addr(void **addr, unsigned int ist)

{

	unsigned int nr;

	bool ist_okay = false;
@@ -644,6 +644,14 @@ static bool get_trap_addr(void **addr, unsigned int ist) 
		}

	}



	if (nr == ARRAY_SIZE(trap_array) &&

	    *addr >= (void *)early_idt_handler_array[0] &&

	    *addr < (void *)early_idt_handler_array[NUM_EXCEPTION_VECTORS]) {

		nr = (*addr - (void *)early_idt_handler_array[0]) /

		     EARLY_IDT_HANDLER_SIZE;

		*addr = (void *)xen_early_idt_handler_array[nr];

	}



	if (WARN_ON(ist != 0 && !ist_okay))

		return false;
@@ -1262,6 +1270,21 @@ asmlinkage __visible void __init xen_start_kernel(void) 
	xen_setup_gdt(0);



	xen_init_irq_ops();



	/* Let's presume PV guests always boot on vCPU with id 0. */

	per_cpu(xen_vcpu_id, 0) = 0;



	/*

	 * Setup xen_vcpu early because idt_setup_early_handler needs it for

	 * local_irq_disable(), irqs_disabled().

	 *

	 * Don't do the full vcpu_info placement stuff until we have

	 * the cpu_possible_mask and a non-dummy shared_info.

	 */

	xen_vcpu_info_reset(0);



	idt_setup_early_handler();



	xen_init_capabilities();



#ifdef CONFIG_X86_LOCAL_APIC
@@ -1295,18 +1318,6 @@ asmlinkage __visible void __init xen_start_kernel(void) 
	 */

	acpi_numa = -1;

#endif

	/* Let's presume PV guests always boot on vCPU with id 0. */

	per_cpu(xen_vcpu_id, 0) = 0;



	/*

	 * Setup xen_vcpu early because start_kernel needs it for

	 * local_irq_disable(), irqs_disabled().

	 *

	 * Don't do the full vcpu_info placement stuff until we have

	 * the cpu_possible_mask and a non-dummy shared_info.

	 */

	xen_vcpu_info_reset(0);



	WARN_ON(xen_cpuhp_setup(xen_cpu_up_prepare_pv, xen_cpu_dead_pv));



	local_irq_disable();

arch/x86/xen/xen-asm_64.S

+14 −0
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 


#include <xen/interface/xen.h>



#include <linux/init.h>

#include <linux/linkage.h>



.macro xen_pv_trap name
@@ -54,6 +55,19 @@ xen_pv_trap entry_INT80_compat 
#endif

xen_pv_trap hypervisor_callback



	__INIT

ENTRY(xen_early_idt_handler_array)

	i = 0

	.rept NUM_EXCEPTION_VECTORS

	pop %rcx

	pop %r11

	jmp early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE

	i = i + 1

	.fill xen_early_idt_handler_array + i*XEN_EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc

	.endr

END(xen_early_idt_handler_array)

	__FINIT



hypercall_iret = hypercall_page + __HYPERVISOR_iret * 32

/*

 * Xen64 iret frame: