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Re: [PATCH v5 3/4] xen/ppc: Implement early serial printk on pseries
- To: Shawn Anastasio <sanastasio@xxxxxxxxxxxxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 24 Jul 2023 13:35:49 +0200
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- Cc: Timothy Pearson <tpearson@xxxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Mon, 24 Jul 2023 11:35:54 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 21.07.2023 19:02, Shawn Anastasio wrote:
> On typical Power VMs (e.g. QEMU's -M pseries), a variety of services
> including an early serial console are provided by Open Firmware.
> Implement the required interfaces to call into Open Firmware and write
> to the serial console.
>
> Since Open Firmware runs in 32-bit Big Endian mode and Xen runs in
> 64-bit Little Endian mode, a thunk is required to save/restore
> any potentially-clobbered registers as well as to perform the
> required endianness switch. Thankfully, linux already has such
> a routine, which was imported into ppc64/of-call.S.
>
> Support for bare metal (PowerNV) will be implemented in a future
> patch.
>
> Signed-off-by: Shawn Anastasio <sanastasio@xxxxxxxxxxxxxxxxxxxxx>
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
with the same remark as for patch 2, plus ...
> --- a/xen/arch/ppc/include/asm/asm-defns.h
> +++ b/xen/arch/ppc/include/asm/asm-defns.h
> @@ -37,4 +37,21 @@
> .long 0xa6037b7d; /* mtsrr1 r11 */
> \
> .long 0x2400004c /* rfid */
>
> +
> +/* Taken from Linux kernel source (arch/powerpc/boot/crt0.S) */
... the introduction of a double blank line here dropped (which I'll
take care of while committing).
Jan
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