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Commit b24e2bdd authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'stable/for-linus-4.0-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip 

Pull xen bugfixes from David Vrabel:
 "Xen regression and bug fixes for 4.0-rc1

   - Fix two regressions introduced in 4.0-rc1 affecting PV/PVH guests
     in certain configurations.

   - Prevent pvscsi frontends bypassing backend checks.

   - Allow privcmd hypercalls to be preempted even on kernel with
     voluntary preemption.  This fixes soft-lockups with long running
     toolstack hypercalls (e.g., when creating/destroying large
     domains)"

* tag 'stable/for-linus-4.0-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  x86/xen: Initialize cr4 shadow for 64-bit PV(H) guests
  xen-scsiback: mark pvscsi frontend request consumed only after last read
  x86/xen: allow privcmd hypercalls to be preempted
  x86/xen: Make sure X2APIC_ENABLE bit of MSR_IA32_APICBASE is not set
parents 84257ce6 5054daa2

arch/x86/kernel/entry_32.S

+3 −0
Original line number Diff line number Diff line
@@ -982,6 +982,9 @@ ENTRY(xen_hypervisor_callback) 
ENTRY(xen_do_upcall)

1:	mov %esp, %eax

	call xen_evtchn_do_upcall

#ifndef CONFIG_PREEMPT

	call xen_maybe_preempt_hcall

#endif

	jmp  ret_from_intr

	CFI_ENDPROC

ENDPROC(xen_hypervisor_callback)

arch/x86/kernel/entry_64.S

+3 −0
Original line number Diff line number Diff line
@@ -1208,6 +1208,9 @@ ENTRY(xen_do_hypervisor_callback) # do_hypervisor_callback(struct *pt_regs) 
	popq %rsp

	CFI_DEF_CFA_REGISTER rsp

	decl PER_CPU_VAR(irq_count)

#ifndef CONFIG_PREEMPT

	call xen_maybe_preempt_hcall

#endif

	jmp  error_exit

	CFI_ENDPROC

END(xen_do_hypervisor_callback)

arch/x86/xen/enlighten.c

+19 −1
Original line number Diff line number Diff line
@@ -1070,6 +1070,23 @@ static inline void xen_write_cr8(unsigned long val) 
	BUG_ON(val);

}

#endif



static u64 xen_read_msr_safe(unsigned int msr, int *err)

{

	u64 val;



	val = native_read_msr_safe(msr, err);

	switch (msr) {

	case MSR_IA32_APICBASE:

#ifdef CONFIG_X86_X2APIC

		if (!(cpuid_ecx(1) & (1 << (X86_FEATURE_X2APIC & 31))))

#endif

			val &= ~X2APIC_ENABLE;

		break;

	}

	return val;

}



static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)

{

	int ret;
@@ -1240,7 +1257,7 @@ static const struct pv_cpu_ops xen_cpu_ops __initconst = { 


	.wbinvd = native_wbinvd,



	.read_msr = native_read_msr_safe,

	.read_msr = xen_read_msr_safe,

	.write_msr = xen_write_msr_safe,



	.read_tsc = native_read_tsc,
@@ -1741,6 +1758,7 @@ asmlinkage __visible void __init xen_start_kernel(void) 
#ifdef CONFIG_X86_32

	i386_start_kernel();

#else

	cr4_init_shadow(); /* 32b kernel does this in i386_start_kernel() */

	x86_64_start_reservations((char *)__pa_symbol(&boot_params));

#endif

}

drivers/xen/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -2,7 +2,7 @@ ifeq ($(filter y, $(CONFIG_ARM) $(CONFIG_ARM64)),) 
obj-$(CONFIG_HOTPLUG_CPU)		+= cpu_hotplug.o

endif

obj-$(CONFIG_X86)			+= fallback.o

obj-y	+= grant-table.o features.o balloon.o manage.o

obj-y	+= grant-table.o features.o balloon.o manage.o preempt.o

obj-y	+= events/

obj-y	+= xenbus/

drivers/xen/preempt.c

0 → 100644
+44 −0
Original line number Diff line number Diff line 
/*

 * Preemptible hypercalls

 *

 * Copyright (C) 2014 Citrix Systems R&D ltd.

 *

 * This source code is free software; you can redistribute it and/or

 * modify it under the terms of the GNU General Public License as

 * published by the Free Software Foundation; either version 2 of the

 * License, or (at your option) any later version.

 */



#include <linux/sched.h>

#include <xen/xen-ops.h>



#ifndef CONFIG_PREEMPT



/*

 * Some hypercalls issued by the toolstack can take many 10s of

 * seconds. Allow tasks running hypercalls via the privcmd driver to

 * be voluntarily preempted even if full kernel preemption is

 * disabled.

 *

 * Such preemptible hypercalls are bracketed by

 * xen_preemptible_hcall_begin() and xen_preemptible_hcall_end()

 * calls.

 */



DEFINE_PER_CPU(bool, xen_in_preemptible_hcall);

EXPORT_SYMBOL_GPL(xen_in_preemptible_hcall);



asmlinkage __visible void xen_maybe_preempt_hcall(void)

{

	if (unlikely(__this_cpu_read(xen_in_preemptible_hcall)

		     && should_resched())) {

		/*

		 * Clear flag as we may be rescheduled on a different

		 * cpu.

		 */

		__this_cpu_write(xen_in_preemptible_hcall, false);

		_cond_resched();

		__this_cpu_write(xen_in_preemptible_hcall, true);

	}

}

#endif /* CONFIG_PREEMPT */