Re: [PATCH] powerpc: Fix up RTAS invocation for new qemu versions

[Thomas Huth <thuth@redhat.com>]

On 04/10/2019 12.38, David Gibson wrote:
> In order to call RTAS functions on powerpc kvm-unit-tests relies on the
> RTAS blob supplied by qemu.  But new versions of qemu don't supply an RTAS
> blob: since the normal way for guests to get RTAS is to call the guest
> firmware's instantiate-rtas function, we now rely on that guest firmware
> to provide the RTAS code itself.
> 
> But qemu-kvm-tests bypasses the usual guest firmware to just run itself,

s/qemu-kvm-tests/kvm-unit-tests/

> so we can't get the rtas blob from SLOF.
> 
> But.. in fact the RTAS blob under qemu is a bit of a sham anyway - it's
> a tiny wrapper that forwards the RTAS call to a hypercall.  So, we can
> just invoke that hypercall directly.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  lib/powerpc/asm/hcall.h |  3 +++
>  lib/powerpc/rtas.c      |  6 +++---
>  powerpc/cstart64.S      | 20 ++++++++++++++++----
>  3 files changed, 22 insertions(+), 7 deletions(-)
> 
> So.. "new versions of qemu" in this case means ones that incorporate
> the pull request I just sent today.
> 
> diff --git a/lib/powerpc/asm/hcall.h b/lib/powerpc/asm/hcall.h
> index a8bd7e3..1173fea 100644
> --- a/lib/powerpc/asm/hcall.h
> +++ b/lib/powerpc/asm/hcall.h
> @@ -24,6 +24,9 @@
>  #define H_RANDOM		0x300
>  #define H_SET_MODE		0x31C
>  
> +#define KVMPPC_HCALL_BASE	0xf000
> +#define KVMPPC_H_RTAS		(KVMPPC_HCALL_BASE + 0x0)
> +
>  #ifndef __ASSEMBLY__
>  /*
>   * hcall_have_broken_sc1 checks if we're on a host with a broken sc1.
> diff --git a/lib/powerpc/rtas.c b/lib/powerpc/rtas.c
> index 2e7e0da..41c0a24 100644
> --- a/lib/powerpc/rtas.c
> +++ b/lib/powerpc/rtas.c
> @@ -46,9 +46,9 @@ void rtas_init(void)
>  	prop = fdt_get_property(dt_fdt(), node,
>  				"linux,rtas-entry", &len);
>  	if (!prop) {
> -		printf("%s: /rtas/linux,rtas-entry: %s\n",
> -				__func__, fdt_strerror(len));
> -		abort();
> +		/* We don't have a qemu provided RTAS blob, enter_rtas
> +		 * will use H_RTAS directly */
> +		return;
>  	}
>  	data = (u32 *)prop->data;
>  	rtas_entry = (unsigned long)fdt32_to_cpu(*data);
> diff --git a/powerpc/cstart64.S b/powerpc/cstart64.S
> index ec673b3..972851f 100644
> --- a/powerpc/cstart64.S
> +++ b/powerpc/cstart64.S
> @@ -121,13 +121,25 @@ halt:
>  
>  .globl enter_rtas
>  enter_rtas:
> +	LOAD_REG_ADDR(r11, rtas_entry)
> +	ld	r10, 0(r11)
> +
> +	cmpdi	r10,0
> +	bne	external_rtas
> +
> +	/* Use H_RTAS directly */
> +	mr	r4,r3
> +	lis	r3,KVMPPC_H_RTAS@h
> +	ori	r3,r3,KVMPPC_H_RTAS@l
> +	b	hcall
> +
> +external_rtas:
> +	/* Use external RTAS blob */
>  	mflr	r0
>  	std	r0, 16(r1)
>  
> -	LOAD_REG_ADDR(r10, rtas_return_loc)
> -	mtlr	r10
> -	LOAD_REG_ADDR(r11, rtas_entry)
> -	ld	r10, 0(r11)
> +	LOAD_REG_ADDR(r11, rtas_return_loc)
> +	mtlr	r11
>  
>  	mfmsr	r11
>  	LOAD_REG_IMMEDIATE(r9, RTAS_MSR_MASK)
> 

With the typo in the commit message fixed:
Reviewed-by: Thomas Huth <thuth@redhat.com>

Paolo, I currently don't have any other kvm-unit-test patches pending,
could you pick this up directly, please?