Re: [kvm-unit-tests PATCH v6 01/10] s390x: saving regs for interrupts

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On 2020-04-27 10:59, David Hildenbrand wrote:
On 24.04.20 12:45, Pierre Morel wrote:
If we use multiple source of interrupts, for example, using SCLP
console to print information while using I/O interrupts, we need
to have a re-entrant register saving interruption handling.

So the primary reason is to print during I/O interrupts (which we
already do, but usually never trigger - handle_io_int())


Instead of saving at a static memory address, let's save the base
registers and the floating point registers on the stack.

".. in case of I/O interrupts".

OK



Note that we keep the static register saving to recover from the
RESET tests.

and for all other types of interrupts.

OK



Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
---
  s390x/cstart64.S | 34 ++++++++++++++++++++++++++++++++--
  1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/s390x/cstart64.S b/s390x/cstart64.S
index 9af6bb3..ba2e67c 100644
--- a/s390x/cstart64.S
+++ b/s390x/cstart64.S
@@ -118,6 +118,36 @@ memsetxc:
  	lmg	%r0, %r15, GEN_LC_SW_INT_GRS
  	.endm
+/* Save registers on the stack (r15), so we can have stacked interrupts. */
+	.macro SAVE_IRQ_REGS

s/SAVE_IRQ_REGS/SAVE_REGS_STACK/ ?

Same for the other macro.

OK


+	/* Allocate a stack frame for 15 integer registers */

not integers. sizeof(int) == 4.

hum, yes, I just do not know from where I took the word "integer" here!.


"doublewords" should be the right s390x speak.

in fact they are named general registers in the POP.
(which indeed are doublewords :) )



+	slgfi   %r15, 15 * 8
+	/* Store all registers from 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 integer */
+	slgfi   %r15, 16 * 8
+	/* 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)
+	.endr
+	.endm

What about the FPC?

Seems I forgot it.
I will update.
Thanks.

Regards,
Pierre


--
Pierre Morel
IBM Lab Boeblingen




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