[kvm-unit-tests PATCH v2 2/8] s390x: Fully commit to stack save area for exceptions

[Janosch Frank <frankja@linux.ibm.com>]

Having two sets of macros for saving registers on exceptions makes
maintaining harder. Also we have limited space in the lowcore to save
stuff and by using the stack as a save area, we can stack exceptions.

So let's use the SAVE/RESTORE_REGS_STACK as the default. When we also
move the diag308 macro over we can remove the old SAVE/RESTORE_REGS
macros.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 lib/s390x/asm-offsets.c   | 14 ++++++++----
 lib/s390x/asm/arch_def.h  | 29 ++++++++++++++++++-----
 lib/s390x/asm/interrupt.h |  4 ++--
 lib/s390x/interrupt.c     | 14 ++++++------
 s390x/cstart64.S          | 19 +++++++++-------
 s390x/macros.S            | 48 +++++++++++++++++++++++----------------
 6 files changed, 82 insertions(+), 46 deletions(-)

diff --git a/lib/s390x/asm-offsets.c b/lib/s390x/asm-offsets.c
index a19f14b9..96cb21cf 100644
--- a/lib/s390x/asm-offsets.c
+++ b/lib/s390x/asm-offsets.c
@@ -70,16 +70,22 @@ int main(void)
 	OFFSET(GEN_LC_ARS_SA, lowcore, ars_sa);
 	OFFSET(GEN_LC_CRS_SA, lowcore, crs_sa);
 	OFFSET(GEN_LC_PGM_INT_TDB, lowcore, pgm_int_tdb);
-	OFFSET(__SF_SIE_CONTROL, stack_frame, empty1[0]);
-	OFFSET(__SF_SIE_SAVEAREA, stack_frame, empty1[1]);
-	OFFSET(__SF_SIE_REASON, stack_frame, empty1[2]);
-	OFFSET(__SF_SIE_FLAGS, stack_frame, empty1[3]);
+	OFFSET(__SF_SIE_CONTROL, stack_frame, argument_area[0]);
+	OFFSET(__SF_SIE_SAVEAREA, stack_frame, argument_area[1]);
+	OFFSET(__SF_SIE_REASON, stack_frame, argument_area[2]);
+	OFFSET(__SF_SIE_FLAGS, stack_frame, argument_area[3]);
 	OFFSET(SIE_SAVEAREA_HOST_GRS, vm_save_area, host.grs[0]);
 	OFFSET(SIE_SAVEAREA_HOST_FPRS, vm_save_area, host.fprs[0]);
 	OFFSET(SIE_SAVEAREA_HOST_FPC, vm_save_area, host.fpc);
 	OFFSET(SIE_SAVEAREA_GUEST_GRS, vm_save_area, guest.grs[0]);
 	OFFSET(SIE_SAVEAREA_GUEST_FPRS, vm_save_area, guest.fprs[0]);
 	OFFSET(SIE_SAVEAREA_GUEST_FPC, vm_save_area, guest.fpc);
+	OFFSET(STACK_FRAME_INT_BACKCHAIN, stack_frame_int, back_chain);
+	OFFSET(STACK_FRAME_INT_FPC, stack_frame_int, fpc);
+	OFFSET(STACK_FRAME_INT_FPRS, stack_frame_int, fprs);
+	OFFSET(STACK_FRAME_INT_CRS, stack_frame_int, crs);
+	OFFSET(STACK_FRAME_INT_GRS0, stack_frame_int, grs0);
+	OFFSET(STACK_FRAME_INT_GRS1, stack_frame_int, grs1);
 
 	return 0;
 }
diff --git a/lib/s390x/asm/arch_def.h b/lib/s390x/asm/arch_def.h
index 9c4e330a..31c2fc66 100644
--- a/lib/s390x/asm/arch_def.h
+++ b/lib/s390x/asm/arch_def.h
@@ -8,13 +8,30 @@
 #ifndef _ASM_S390X_ARCH_DEF_H_
 #define _ASM_S390X_ARCH_DEF_H_
 
-/*
- * We currently only specify the stack frame members needed for the
- * SIE library code.
- */
 struct stack_frame {
-	unsigned long back_chain;
-	unsigned long empty1[5];
+	struct stack_frame *back_chain;
+	u64 reserved;
+	/* GRs 2 - 5 */
+	unsigned long argument_area[4];
+	/* GRs 6 - 15 */
+	unsigned long grs[10];
+	/* FPRs 0, 2, 4, 6 */
+	s64  fprs[4];
+};
+
+struct stack_frame_int {
+	struct stack_frame *back_chain;
+	u64 reserved;
+	/*
+	 * The GRs are offset compatible with struct stack_frame so we
+	 * can easily fetch GR14 for backtraces.
+	 */
+	u64 grs0[14];
+	u64 grs1[2];
+	u32 res;
+	u32 fpc;
+	u64 fprs[16];
+	u64 crs[16];
 };
 
 struct psw {
diff --git a/lib/s390x/asm/interrupt.h b/lib/s390x/asm/interrupt.h
index 1a2e2cd8..31e4766d 100644
--- a/lib/s390x/asm/interrupt.h
+++ b/lib/s390x/asm/interrupt.h
@@ -14,8 +14,8 @@
 #define EXT_IRQ_SERVICE_SIG	0x2401
 
 void register_pgm_cleanup_func(void (*f)(void));
-void handle_pgm_int(void);
-void handle_ext_int(void);
+void handle_pgm_int(struct stack_frame_int *stack);
+void handle_ext_int(struct stack_frame_int *stack);
 void handle_mcck_int(void);
 void handle_io_int(void);
 void handle_svc_int(void);
diff --git a/lib/s390x/interrupt.c b/lib/s390x/interrupt.c
index 1ce36073..a59df80e 100644
--- a/lib/s390x/interrupt.c
+++ b/lib/s390x/interrupt.c
@@ -56,7 +56,7 @@ void register_pgm_cleanup_func(void (*f)(void))
 	pgm_cleanup_func = f;
 }
 
-static void fixup_pgm_int(void)
+static void fixup_pgm_int(struct stack_frame_int *stack)
 {
 	/* If we have an error on SIE we directly move to sie_exit */
 	if (lc->pgm_old_psw.addr >= (uint64_t)&sie_entry &&
@@ -76,7 +76,7 @@ static void fixup_pgm_int(void)
 		/* Handling for iep.c test case. */
 		if (lc->trans_exc_id & 0x80UL && lc->trans_exc_id & 0x04UL &&
 		    !(lc->trans_exc_id & 0x08UL))
-			lc->pgm_old_psw.addr = lc->sw_int_grs[14];
+			lc->pgm_old_psw.addr = stack->grs0[12];
 		break;
 	case PGM_INT_CODE_SEGMENT_TRANSLATION:
 	case PGM_INT_CODE_PAGE_TRANSLATION:
@@ -115,7 +115,7 @@ static void fixup_pgm_int(void)
 	/* suppressed/terminated/completed point already at the next address */
 }
 
-void handle_pgm_int(void)
+void handle_pgm_int(struct stack_frame_int *stack)
 {
 	if (!pgm_int_expected) {
 		/* Force sclp_busy to false, otherwise we will loop forever */
@@ -130,10 +130,10 @@ void handle_pgm_int(void)
 	if (pgm_cleanup_func)
 		(*pgm_cleanup_func)();
 	else
-		fixup_pgm_int();
+		fixup_pgm_int(stack);
 }
 
-void handle_ext_int(void)
+void handle_ext_int(struct stack_frame_int *stack)
 {
 	if (!ext_int_expected &&
 	    lc->ext_int_code != EXT_IRQ_SERVICE_SIG) {
@@ -143,13 +143,13 @@ void handle_ext_int(void)
 	}
 
 	if (lc->ext_int_code == EXT_IRQ_SERVICE_SIG) {
-		lc->sw_int_crs[0] &= ~(1UL << 9);
+		stack->crs[0] &= ~(1UL << 9);
 		sclp_handle_ext();
 	} else {
 		ext_int_expected = false;
 	}
 
-	if (!(lc->sw_int_crs[0] & CR0_EXTM_MASK))
+	if (!(stack->crs[0] & CR0_EXTM_MASK))
 		lc->ext_old_psw.mask &= ~PSW_MASK_EXT;
 }
 
diff --git a/s390x/cstart64.S b/s390x/cstart64.S
index ace0c0d9..35d20293 100644
--- a/s390x/cstart64.S
+++ b/s390x/cstart64.S
@@ -92,33 +92,36 @@ memsetxc:
 
 .section .text
 pgm_int:
-	SAVE_REGS
+	SAVE_REGS_STACK
+	lgr     %r2, %r15
 	brasl	%r14, handle_pgm_int
-	RESTORE_REGS
+	RESTORE_REGS_STACK
 	lpswe	GEN_LC_PGM_OLD_PSW
 
 ext_int:
-	SAVE_REGS
+	SAVE_REGS_STACK
+	lgr     %r2, %r15
 	brasl	%r14, handle_ext_int
-	RESTORE_REGS
+	RESTORE_REGS_STACK
 	lpswe	GEN_LC_EXT_OLD_PSW
 
 mcck_int:
-	SAVE_REGS
+	SAVE_REGS_STACK
 	brasl	%r14, handle_mcck_int
-	RESTORE_REGS
+	RESTORE_REGS_STACK
 	lpswe	GEN_LC_MCCK_OLD_PSW
 
 io_int:
 	SAVE_REGS_STACK
+	lgr     %r2, %r15
 	brasl	%r14, handle_io_int
 	RESTORE_REGS_STACK
 	lpswe	GEN_LC_IO_OLD_PSW
 
 svc_int:
-	SAVE_REGS
+	SAVE_REGS_STACK
 	brasl	%r14, handle_svc_int
-	RESTORE_REGS
+	RESTORE_REGS_STACK
 	lpswe	GEN_LC_SVC_OLD_PSW
 
 	.align	8
diff --git a/s390x/macros.S b/s390x/macros.S
index e51a557a..d7eeeb55 100644
--- a/s390x/macros.S
+++ b/s390x/macros.S
@@ -3,9 +3,10 @@
  * s390x assembly macros
  *
  * Copyright (c) 2017 Red Hat Inc
- * Copyright (c) 2020 IBM Corp.
+ * Copyright (c) 2020, 2021 IBM Corp.
  *
  * Authors:
+ *  Janosch Frank <frankja@linux.ibm.com>
  *  Pierre Morel <pmorel@linux.ibm.com>
  *  David Hildenbrand <david@redhat.com>
  */
@@ -41,36 +42,45 @@
 
 /* Save registers on the stack (r15), so we can have stacked interrupts. */
 	.macro SAVE_REGS_STACK
-	/* Allocate a stack frame for 15 general registers */
-	slgfi   %r15, 15 * 8
+	/* Allocate a full stack frame */
+	slgfi   %r15, 32 * 8 + 4 * 8
 	/* Store registers r0 to r14 on the stack */
-	stmg    %r0, %r14, 0(%r15)
-	/* Allocate a stack frame for 16 floating point registers */
-	/* The size of a FP register is the size of an double word */
-	slgfi   %r15, 16 * 8
+	stmg    %r2, %r15, STACK_FRAME_INT_GRS0(%r15)
+	stg     %r0, STACK_FRAME_INT_GRS1(%r15)
+	stg     %r1, STACK_FRAME_INT_GRS1 + 8(%r15)
+	/* Store the gr15 value before we allocated the new stack */
+	lgr     %r0, %r15
+	algfi   %r0, 32 * 8 + 4 * 8
+	stg     %r0, 13 * 8 + STACK_FRAME_INT_GRS0(%r15)
+	stg     %r0, STACK_FRAME_INT_BACKCHAIN(%r15)
+	/*
+	 * Store CR0 and load initial CR0 so AFP is active and we can
+	 * access all fprs to save them.
+	 */
+	stctg   %c0,%c15,STACK_FRAME_INT_CRS(%r15)
+	larl	%r1, initial_cr0
+	lctlg	%c0, %c0, 0(%r1)
 	/* Save fp register on stack: offset to SP is multiple of reg number */
 	.irp i, 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
-	std	\i, \i * 8(%r15)
+	std	\i, \i * 8 + STACK_FRAME_INT_FPRS(%r15)
 	.endr
-	/* Save fpc, but keep stack aligned on 64bits */
-	slgfi   %r15, 8
-	stfpc	0(%r15)
+	/* Save fpc */
+	stfpc	STACK_FRAME_INT_FPC(%r15)
 	.endm
 
 /* Restore the register in reverse order */
 	.macro RESTORE_REGS_STACK
 	/* Restore fpc */
-	lfpc	0(%r15)
-	algfi	%r15, 8
+	lfpc	STACK_FRAME_INT_FPC(%r15)
 	/* Restore fp register from stack: SP still where it was left */
 	/* and offset to SP is a multiple of reg number */
 	.irp i, 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
-	ld	\i, \i * 8(%r15)
+	ld	\i, \i * 8 + STACK_FRAME_INT_FPRS(%r15)
 	.endr
-	/* Now that we're done, rewind the stack pointer by 16 double word */
-	algfi   %r15, 16 * 8
+	/* Load CR0 back */
+	lctlg	%c0, %c15, STACK_FRAME_INT_CRS(%r15)
 	/* Load the registers from stack */
-	lmg     %r0, %r14, 0(%r15)
-	/* Rewind the stack by 15 double word */
-	algfi   %r15, 15 * 8
+	lg      %r0, STACK_FRAME_INT_GRS1(%r15)
+	lg      %r1, STACK_FRAME_INT_GRS1 + 8(%r15)
+	lmg     %r2, %r15, STACK_FRAME_INT_GRS0(%r15)
 	.endm
-- 
2.25.1