[kvm-unit-tests PATCH 5/5] lib: s390x: Handle debug prints for SIE exceptions correctly

Janosch Frank
2022-11-23T08:47:24Z

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