* [kvm-unit-tests PATCH] s390x: snippets: c: Load initial cr0
@ 2022-03-31 12:55 Janosch Frank
2022-03-31 14:58 ` Claudio Imbrenda
0 siblings, 1 reply; 2+ messages in thread
From: Janosch Frank @ 2022-03-31 12:55 UTC (permalink / raw)
To: kvm; +Cc: linux-s390, imbrenda, david, thuth
As soon as we use C we need to set the AFP bit in cr0 so we can use
all fprs.
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
---
s390x/snippets/c/cstart.S | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/s390x/snippets/c/cstart.S b/s390x/snippets/c/cstart.S
index aaa5380c..a7d4cd42 100644
--- a/s390x/snippets/c/cstart.S
+++ b/s390x/snippets/c/cstart.S
@@ -12,6 +12,8 @@
.section .init
.globl start
start:
+ larl %r1, initial_cr0
+ lctlg %c0, %c0, 0(%r1)
/* XOR all registers with themselves to clear them fully. */
.irp i, 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
xgr \i,\i
@@ -34,3 +36,7 @@ exit:
/* For now let's only use cpu 0 in snippets so this will always work. */
xgr %r0, %r0
sigp %r2, %r0, SIGP_STOP
+
+initial_cr0:
+ /* enable AFP-register control, so FP regs (+BFP instr) can be used */
+ .quad 0x0000000000040000
--
2.32.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [kvm-unit-tests PATCH] s390x: snippets: c: Load initial cr0
2022-03-31 12:55 [kvm-unit-tests PATCH] s390x: snippets: c: Load initial cr0 Janosch Frank
@ 2022-03-31 14:58 ` Claudio Imbrenda
0 siblings, 0 replies; 2+ messages in thread
From: Claudio Imbrenda @ 2022-03-31 14:58 UTC (permalink / raw)
To: Janosch Frank; +Cc: kvm, linux-s390, david, thuth
On Thu, 31 Mar 2022 12:55:15 +0000
Janosch Frank <frankja@linux.ibm.com> wrote:
> As soon as we use C we need to set the AFP bit in cr0 so we can use
> all fprs.
>
seems like a good idea
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> ---
> s390x/snippets/c/cstart.S | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/s390x/snippets/c/cstart.S b/s390x/snippets/c/cstart.S
> index aaa5380c..a7d4cd42 100644
> --- a/s390x/snippets/c/cstart.S
> +++ b/s390x/snippets/c/cstart.S
> @@ -12,6 +12,8 @@
> .section .init
> .globl start
> start:
> + larl %r1, initial_cr0
> + lctlg %c0, %c0, 0(%r1)
> /* XOR all registers with themselves to clear them fully. */
> .irp i, 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
> xgr \i,\i
> @@ -34,3 +36,7 @@ exit:
> /* For now let's only use cpu 0 in snippets so this will always work. */
> xgr %r0, %r0
> sigp %r2, %r0, SIGP_STOP
> +
> +initial_cr0:
> + /* enable AFP-register control, so FP regs (+BFP instr) can be used */
> + .quad 0x0000000000040000
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