[kvm-unit-tests PATCH v2 7/7] lib: s390x: Handle debug prints for SIE exceptions correctly

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

When we leave SIE due to an exception, we'll still have guest values
in registers 0 - 13 and that's not clearly portraied in our debug
prints. So let's fix that.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
---
 lib/s390x/interrupt.c | 46 ++++++++++++++++++++++++++++++++++++++-----
 lib/s390x/sie.h       |  2 ++
 s390x/cpu.S           |  6 ++++--
 3 files changed, 47 insertions(+), 7 deletions(-)

diff --git a/lib/s390x/interrupt.c b/lib/s390x/interrupt.c
index dadb7415..ff47c2c2 100644
--- a/lib/s390x/interrupt.c
+++ b/lib/s390x/interrupt.c
@@ -9,6 +9,7 @@
  */
 #include <libcflat.h>
 #include <asm/barrier.h>
+#include <asm/asm-offsets.h>
 #include <sclp.h>
 #include <interrupt.h>
 #include <sie.h>
@@ -188,9 +189,12 @@ static void print_storage_exception_information(void)
 	}
 }
 
-static void print_int_regs(struct stack_frame_int *stack)
+static void print_int_regs(struct stack_frame_int *stack, bool sie)
 {
+	struct kvm_s390_sie_block *sblk;
+
 	printf("\n");
+	printf("%s\n", sie ? "Guest registers:" : "Host registers:");
 	printf("GPRS:\n");
 	printf("%016lx %016lx %016lx %016lx\n",
 	       stack->grs1[0], stack->grs1[1], stack->grs0[0], stack->grs0[1]);
@@ -198,24 +202,56 @@ static void print_int_regs(struct stack_frame_int *stack)
 	       stack->grs0[2], stack->grs0[3], stack->grs0[4], stack->grs0[5]);
 	printf("%016lx %016lx %016lx %016lx\n",
 	       stack->grs0[6], stack->grs0[7], stack->grs0[8], stack->grs0[9]);
-	printf("%016lx %016lx %016lx %016lx\n",
-	       stack->grs0[10], stack->grs0[11], stack->grs0[12], stack->grs0[13]);
+
+	if (sie) {
+		sblk = (struct kvm_s390_sie_block *)stack->grs0[12];
+		printf("%016lx %016lx %016lx %016lx\n",
+		       stack->grs0[10], stack->grs0[11], sblk->gg14, sblk->gg15);
+	} else {
+		printf("%016lx %016lx %016lx %016lx\n",
+		       stack->grs0[10], stack->grs0[11], stack->grs0[12], stack->grs0[13]);
+	}
+
 	printf("\n");
 }
 
 static void print_pgm_info(struct stack_frame_int *stack)
 
 {
-	bool in_sie;
+	bool in_sie, in_sie_gregs;
+	struct vm_save_area *vregs;
 
 	in_sie = (lowcore.pgm_old_psw.addr >= (uintptr_t)sie_entry &&
 		  lowcore.pgm_old_psw.addr <= (uintptr_t)sie_exit);
+	in_sie_gregs = (lowcore.pgm_old_psw.addr >= (uintptr_t)sie_entry_gregs &&
+			lowcore.pgm_old_psw.addr <= (uintptr_t)sie_exit_gregs);
 
 	printf("\n");
 	printf("Unexpected program interrupt %s: %#x on cpu %d at %#lx, ilen %d\n",
 	       in_sie ? "in SIE" : "",
 	       lowcore.pgm_int_code, stap(), lowcore.pgm_old_psw.addr, lowcore.pgm_int_id);
-	print_int_regs(stack);
+
+	/*
+	 * If we fall out of SIE before loading the host registers,
+	 * then we need to do it here so we print the host registers
+	 * and not the guest registers.
+	 *
+	 * Back tracing is actually not a problem since SIE restores gr15.
+	 */
+	if (in_sie_gregs) {
+		print_int_regs(stack, true);
+		vregs = *((struct vm_save_area **)(stack->grs0[13] + __SF_SIE_SAVEAREA));
+
+		/*
+		 * The grs are not linear on the interrupt stack frame.
+		 * We copy 0 and 1 here and 2 - 15 with the memcopy below.
+		 */
+		stack->grs1[0] = vregs->host.grs[0];
+		stack->grs1[1] = vregs->host.grs[1];
+		/*  2 - 15 */
+		memcpy(stack->grs0, &vregs->host.grs[2], sizeof(stack->grs0) - 8);
+	}
+	print_int_regs(stack, false);
 	dump_stack();
 
 	/* Dump stack doesn't end with a \n so we add it here instead */
diff --git a/lib/s390x/sie.h b/lib/s390x/sie.h
index a27a8401..147cb0f2 100644
--- a/lib/s390x/sie.h
+++ b/lib/s390x/sie.h
@@ -273,6 +273,8 @@ struct vm {
 
 extern void sie_entry(void);
 extern void sie_exit(void);
+extern void sie_entry_gregs(void);
+extern void sie_exit_gregs(void);
 extern void sie64a(struct kvm_s390_sie_block *sblk, struct vm_save_area *save_area);
 void sie(struct vm *vm);
 void sie_expect_validity(struct vm *vm);
diff --git a/s390x/cpu.S b/s390x/cpu.S
index 45bd551a..9155b044 100644
--- a/s390x/cpu.S
+++ b/s390x/cpu.S
@@ -82,7 +82,8 @@ sie64a:
 	# Store scb and save_area pointer into stack frame
 	stg	%r2,__SF_SIE_CONTROL(%r15)	# save control block pointer
 	stg	%r3,__SF_SIE_SAVEAREA(%r15)	# save guest register save area
-
+.globl sie_entry_gregs
+sie_entry_gregs:
 	# Load guest's gprs, fprs and fpc
 	.irp i, 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
 	ld	\i, \i * 8 + SIE_SAVEAREA_GUEST_FPRS(%r3)
@@ -121,7 +122,8 @@ sie_exit:
 	.endr
 	lfpc	SIE_SAVEAREA_HOST_FPC(%r14)
 	lmg	%r0,%r14,SIE_SAVEAREA_HOST_GRS(%r14)	# restore kernel registers
-
+.globl sie_exit_gregs
+sie_exit_gregs:
 	br	%r14
 
 	.align	8
-- 
2.34.1