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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: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Thomas 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
This commit is contained in:
Juergen Gross 2017-11-24 09:42:21 +01:00 committed by Thomas Gleixner
parent 9d0b62328d
commit 42b3a4cb56
4 changed files with 53 additions and 14 deletions
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12
arch/x86/include/asm/segment.h
View File

@ -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.

4
arch/x86/mm/extable.c
View File

@ -1,6 +1,7 @@
#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;
/*

37
arch/x86/xen/enlighten_pv.c
View File

@ -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();

14
arch/x86/xen/xen-asm_64.S
View File

@ -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: