Re: [PATCH v2 04/10] ppc/spapr: Remove copy-paste from pa-features

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Mar 12, 2024 at 11:14:13PM +1000, Nicholas Piggin wrote:
> TCG does not support copy/paste instructions. Remove it from
> ibm,pa-features. This has never been implemented under TCG or
> practically usable under KVM, so it won't be missed.

As with the previous patch, the specific circumstances here justify
breaking the general rule.

> 
> Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
>  hw/ppc/spapr.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 3108d7c532..4192cd8d6c 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -237,6 +237,10 @@ static void spapr_dt_pa_features(SpaprMachineState *spapr,
>       * SSO (SAO) ordering is supported on KVM and thread=single hosts,
>       * but not MTTCG, so disable it. To advertise it, a cap would have
>       * to be added, or support implemented for MTTCG.
> +     *
> +     * Copy/paste is not supported by TCG, so it is not advertised. KVM
> +     * can execute them but it has no accelerator drivers which are usable,
> +     * so there isn't much need for it anyway.
>       */
>  
>      uint8_t pa_features_206[] = { 6, 0,
> @@ -260,8 +264,8 @@ static void spapr_dt_pa_features(SpaprMachineState *spapr,
>          0x80, 0x00, 0x80, 0x00, 0x80, 0x00, /* 24 - 29 */
>          /* 30: MMR, 32: LE atomic, 34: EBB + ext EBB */
>          0x80, 0x00, 0x80, 0x00, 0xC0, 0x00, /* 30 - 35 */
> -        /* 36: SPR SO, 38: Copy/Paste, 40: Radix MMU */
> -        0x80, 0x00, 0x80, 0x00, 0x80, 0x00, /* 36 - 41 */
> +        /* 36: SPR SO, 40: Radix MMU */
> +        0x80, 0x00, 0x00, 0x00, 0x80, 0x00, /* 36 - 41 */
>          /* 42: PM, 44: PC RA, 46: SC vec'd */
>          0x80, 0x00, 0x80, 0x00, 0x80, 0x00, /* 42 - 47 */
>          /* 48: SIMD, 50: QP BFP, 52: String */

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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