linux-kernel - Re: [PATCH v2 3/6] irqchip/gic-v4.1: Ensure L2 vPE table is allocated at RD level

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Date:   Thu, 13 Feb 2020 14:22:07 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Zenghui Yu <yuzenghui@...wei.com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.cs.columbia.edu, tglx@...utronix.de,
        jason@...edaemon.net, wanghaibin.wang@...wei.com
Subject: Re: [PATCH v2 3/6] irqchip/gic-v4.1: Ensure L2 vPE table is allocated
 at RD level

Hi Zenghui,

On 2020-02-06 07:57, Zenghui Yu wrote:
> In GICv4, we will ensure that level2 vPE table memory is allocated
> for the specified vpe_id on all v4 ITS, in its_alloc_vpe_table().
> This still works well for the typical GICv4.1 implementation, where
> the new vPE table is shared between the ITSs and the RDs.
> 
> To make it explicit, let us introduce allocate_vpe_l2_table() to
> make sure that the L2 tables are allocated on all v4.1 RDs. We're
> likely not need to allocate memory in it because the vPE table is
> shared and (L2 table is) already allocated at ITS level, except
> for the case where the ITS doesn't share anything (say SVPET == 0,
> practically unlikely but architecturally allowed).
> 
> The implementation of allocate_vpe_l2_table() is mostly copied from
> its_alloc_table_entry().
> 
> Signed-off-by: Zenghui Yu <yuzenghui@...wei.com>
> ---
>  drivers/irqchip/irq-gic-v3-its.c | 80 ++++++++++++++++++++++++++++++++
>  1 file changed, 80 insertions(+)
> 
> diff --git a/drivers/irqchip/irq-gic-v3-its.c 
> b/drivers/irqchip/irq-gic-v3-its.c
> index 0f1fe56ce0af..ae4e7b355b46 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -2443,6 +2443,72 @@ static u64 
> inherit_vpe_l1_table_from_rd(cpumask_t **mask)
>  	return 0;
>  }
> 
> +static bool allocate_vpe_l2_table(int cpu, u32 id)
> +{
> +	void __iomem *base = gic_data_rdist_cpu(cpu)->rd_base;
> +	u64 val, gpsz, npg;
> +	unsigned int psz, esz, idx;
> +	struct page *page;
> +	__le64 *table;
> +
> +	if (!gic_rdists->has_rvpeid)
> +		return true;
> +
> +	val  = gits_read_vpropbaser(base + SZ_128K + GICR_VPROPBASER);

Having rebased the rest of the GICv4.1 series on top of -rc1, I've hit a 
small
issue right here. I run a FVP model that only spawns 4 CPUs, while the 
DT has
8 of them. This means that online_cpus = 4, and possible_cpus = 8.

So in my case, half of the RDs have base == NULL, and things stop 
quickly.

I plan to queue the following:

diff --git a/drivers/irqchip/irq-gic-v3-its.c 
b/drivers/irqchip/irq-gic-v3-its.c
index d85dc8dcb0ad..7656b353a95f 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -2526,6 +2526,10 @@ static bool allocate_vpe_l2_table(int cpu, u32 
id)
  	if (!gic_rdists->has_rvpeid)
  		return true;

+	/* Skip non-present CPUs */
+	if (!base)
+		return true;
+
  	val  = gicr_read_vpropbaser(base + SZ_128K + GICR_VPROPBASER);

  	esz  = FIELD_GET(GICR_VPROPBASER_4_1_ENTRY_SIZE, val) + 1;


Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...