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Commit c771320e authored by Martin Schwidefsky's avatar Martin Schwidefsky Committed by Heiko Carstens
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s390/mm,kvm: improve detection of KVM guest faults 



The identification of guest fault currently relies on the PF_VCPU flag.
This is set in guest_entry_irqoff and cleared in guest_exit_irqoff.
Both functions are called by __vcpu_run, the PF_VCPU flag is set for
quite a lot of kernel code outside of the guest execution.

Replace the PF_VCPU scheme with the PIF_GUEST_FAULT in the pt_regs and
make the program check handler code in entry.S set the bit only for
exception that occurred between the .Lsie_gmap and .Lsie_done labels.

Reviewed-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
parent cefbeb5d

arch/s390/include/asm/ptrace.h

+2 −0
Original line number Diff line number Diff line
@@ -13,10 +13,12 @@ 
#define PIF_SYSCALL		0	/* inside a system call */

#define PIF_PER_TRAP		1	/* deliver sigtrap on return to user */

#define PIF_SYSCALL_RESTART	2	/* restart the current system call */

#define PIF_GUEST_FAULT		3	/* indicates program check in sie64a */



#define _PIF_SYSCALL		_BITUL(PIF_SYSCALL)

#define _PIF_PER_TRAP		_BITUL(PIF_PER_TRAP)

#define _PIF_SYSCALL_RESTART	_BITUL(PIF_SYSCALL_RESTART)

#define _PIF_GUEST_FAULT	_BITUL(PIF_GUEST_FAULT)



#ifndef __ASSEMBLY__

arch/s390/kernel/entry.S

+5 −2
Original line number Diff line number Diff line
@@ -518,6 +518,7 @@ ENTRY(pgm_check_handler) 
	stmg	%r8,%r15,__LC_SAVE_AREA_SYNC

	lg	%r10,__LC_LAST_BREAK

	lg	%r12,__LC_CURRENT

	lghi	%r11,0

	larl	%r13,cleanup_critical

	lmg	%r8,%r9,__LC_PGM_OLD_PSW

	tmhh	%r8,0x0001		# test problem state bit
@@ -532,6 +533,7 @@ ENTRY(pgm_check_handler) 
	ni	__SIE_PROG0C+3(%r14),0xfe	# no longer in SIE

	lctlg	%c1,%c1,__LC_USER_ASCE		# load primary asce

	larl	%r9,sie_exit			# skip forward to sie_exit

	lghi	%r11,_PIF_GUEST_FAULT

#endif

0:	tmhh	%r8,0x4000		# PER bit set in old PSW ?

	jnz	1f			# -> enabled, can't be a double fault
@@ -549,13 +551,14 @@ ENTRY(pgm_check_handler) 
	jz	3f

	mvc	__THREAD_trap_tdb(256,%r14),0(%r13)

3:	stg	%r10,__THREAD_last_break(%r14)

4:	la	%r11,STACK_FRAME_OVERHEAD(%r15)

4:	lgr	%r13,%r11

	la	%r11,STACK_FRAME_OVERHEAD(%r15)

	stmg	%r0,%r7,__PT_R0(%r11)

	mvc	__PT_R8(64,%r11),__LC_SAVE_AREA_SYNC

	stmg	%r8,%r9,__PT_PSW(%r11)

	mvc	__PT_INT_CODE(4,%r11),__LC_PGM_ILC

	mvc	__PT_INT_PARM_LONG(8,%r11),__LC_TRANS_EXC_CODE

	xc	__PT_FLAGS(8,%r11),__PT_FLAGS(%r11)

	stg	%r13,__PT_FLAGS(%r11)

	stg	%r10,__PT_ARGS(%r11)

	tm	__LC_PGM_ILC+3,0x80	# check for per exception

	jz	5f

arch/s390/mm/fault.c

+3 −3
Original line number Diff line number Diff line
@@ -117,7 +117,7 @@ static inline int user_space_fault(struct pt_regs *regs) 
		return 1;

	if (trans_exc_code == 2) /* secondary space -> set_fs */

		return current->thread.mm_segment.ar4;

	if (current->flags & PF_VCPU)

	if (test_pt_regs_flag(regs, PIF_GUEST_FAULT))

		return 1;

	return 0;

}
@@ -209,7 +209,7 @@ static void dump_fault_info(struct pt_regs *regs) 
		pr_cont("kernel ");

	}

#ifdef CONFIG_PGSTE

	else if ((current->flags & PF_VCPU) && S390_lowcore.gmap) {

	else if (test_pt_regs_flag(regs, PIF_GUEST_FAULT)) {

		struct gmap *gmap = (struct gmap *)S390_lowcore.gmap;

		asce = gmap->asce;

		pr_cont("gmap ");
@@ -438,7 +438,7 @@ static inline int do_exception(struct pt_regs *regs, int access) 
	down_read(&mm->mmap_sem);



#ifdef CONFIG_PGSTE

	gmap = (current->flags & PF_VCPU) ?

	gmap = test_pt_regs_flag(regs, PIF_GUEST_FAULT) ?

		(struct gmap *) S390_lowcore.gmap : NULL;

	if (gmap) {

		current->thread.gmap_addr = address;