[Skiboot] [PATCH 01/11] xive/p9: Introduce XIVE_INT_ORDER

[Gustavo Romero]

Hi Cédric,

On 6/4/20 10:21 AM, Cédric Le Goater wrote:
> The size of the interrupt number space is constrained by the block and
> index fields of the trigger data exchanged between source units and
> the XIVE IC. These are respectively 4 and 28 bits, which gives us a 32
> bits interrupt number space. But the XICS emulation requires 8 bits to
> encode the CPPR value. The system interrupt number space is therefore
> constrained to 24 bits and on a chip, to 20 bits because the XIVE
> driver configures the HW to use one block per chip.
> 
> XIVE_INT_ORDER defines the size of the interrupt number space : 1M per
> chip.
> 
> To control these interrupts, the driver defines in the VC BAR of the
> controller a range of 384G of ESB pages giving access to 3M interrupts.
> The VSD for the memory table is smaller than the index and accesses to
> some ESB pages are not backed by a memory table structure. If such an
> access occurred, it would result in a FIR.
> 
> It never happened but this is something to fix with a finer configuration
> of the VC BAR.
> 
> Signed-off-by: Cédric Le Goater <clg at kaod.org>
> ---
>   hw/xive.c | 32 ++++++++++++++++++--------------
>   1 file changed, 18 insertions(+), 14 deletions(-)
> 
> diff --git a/hw/xive.c b/hw/xive.c
> index 9a36f1ab2111..b9cdc4b0e317 100644
> --- a/hw/xive.c
> +++ b/hw/xive.c
> @@ -146,18 +146,22 @@
>    * so we could potentially make the IVT size twice as big, but for now
>    * we will simply share it and ensure we don't hand out IPIs that
>    * overlap the HW interrupts.
> + *
> + * TODO: adjust the VC BAR range for IPI ESBs on this value
>    */
> -#define MAX_INT_ENTRIES		(1 * 1024 * 1024)
> +
> +#define XIVE_INT_ORDER		20 /* 1M interrupts */
> +#define XIVE_INT_COUNT		(1ul << XIVE_INT_ORDER)
>   
>   /*
>    * First interrupt number, also the first logical interrupt number
> - * allocated by Linux
> + * allocated by Linux (the first numbers are reserved for ISA)
>    */
>   #define XIVE_INT_FIRST		0x10
>   
>   /* Corresponding direct table sizes */
> -#define SBE_SIZE	(MAX_INT_ENTRIES / 4)
> -#define IVT_SIZE	(MAX_INT_ENTRIES * 8)
> +#define SBE_SIZE	        (XIVE_INT_COUNT / 4)
> +#define IVT_SIZE	        (XIVE_INT_COUNT * 8)

I thought VC BAR would configure ESB (aka SBE) plus END, not IVT (aka EAS
or EAST), since the other FSM (related to ESn and ESe) is associated with
END and not with EAS, plus END size is 8 bytes and EAS size is 2 bytes.

So is "IVT_" used in that context correct?


Best regards,
Gustavo