linux-kernel - Re: [PATCH 06/10] irqchip/gic-v3-its: Allow use of pre-programmed LPI tables

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Date:   Mon, 24 Sep 2018 13:52:46 +0100
From:   Julien Thierry <julien.thierry@....com>
To:     Marc Zyngier <marc.zyngier@....com>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Jeremy Linton <jeremy.linton@....com>,
        Jeffrey Hugo <jhugo@...eaurora.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>
Subject: Re: [PATCH 06/10] irqchip/gic-v3-its: Allow use of pre-programmed LPI
 tables



On 21/09/18 20:59, Marc Zyngier wrote:
> In order to cope with kexec and GICv3, let's try and spot when
> we're booting with LPIs already enabled, and the tables already
> programmed into the redistributors.
> 
> This code is currently guarded by a predicate that is always false,
> meaning this is not functionnal just yet.
> 

Reviewed-by: Julien Thierry <julien.thierry@....com>

> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> ---
>   drivers/irqchip/irq-gic-v3-its.c | 73 ++++++++++++++++++++++++++------
>   1 file changed, 61 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index c2f1138034fd..e29ce9f2ac8a 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -52,6 +52,7 @@
>   #define ITS_FLAGS_SAVE_SUSPEND_STATE		(1ULL << 3)
>   
>   #define RDIST_FLAGS_PROPBASE_NEEDS_FLUSHING	(1 << 0)
> +#define RDIST_FLAGS_RD_TABLES_PREALLOCATED	(1 << 1)
>   
>   static u32 lpi_id_bits;
>   
> @@ -1628,18 +1629,32 @@ static void its_free_prop_table(struct page *prop_page)
>   
>   static int __init its_alloc_lpi_prop_table(void)
>   {
> -	struct page *page;
> +	if (gic_rdists->flags & RDIST_FLAGS_RD_TABLES_PREALLOCATED) {
> +		u64 val;
>   
> -	lpi_id_bits = min_t(u32, GICD_TYPER_ID_BITS(gic_rdists->gicd_typer),
> -				ITS_MAX_LPI_NRBITS);
> -	page = its_allocate_prop_table(GFP_NOWAIT);
> -	if (!page) {
> -		pr_err("Failed to allocate PROPBASE\n");
> -		return -ENOMEM;
> -	}
> +		val = gicr_read_propbaser(gic_data_rdist_rd_base() + GICR_PROPBASER);
> +		lpi_id_bits = (val & GICR_PROPBASER_IDBITS_MASK) + 1;
>   
> -	gic_rdists->prop_table_pa = page_to_phys(page);
> -	gic_rdists->prop_table_va = page_address(page);
> +		gic_rdists->prop_table_pa = val & GENMASK_ULL(51, 12);
> +		gic_rdists->prop_table_va = memremap(gic_rdists->prop_table_pa,
> +						     LPI_PROPBASE_SZ,
> +						     MEMREMAP_WB);
> +		gic_reset_prop_table(gic_rdists->prop_table_va);
> +	} else {
> +		struct page *page;
> +
> +		lpi_id_bits = min_t(u32,
> +				    GICD_TYPER_ID_BITS(gic_rdists->gicd_typer),
> +				    ITS_MAX_LPI_NRBITS);
> +		page = its_allocate_prop_table(GFP_NOWAIT);
> +		if (!page) {
> +			pr_err("Failed to allocate PROPBASE\n");
> +			return -ENOMEM;
> +		}
> +
> +		gic_rdists->prop_table_pa = page_to_phys(page);
> +		gic_rdists->prop_table_va = page_address(page);
> +	}
>   
>   	pr_info("GICv3: using LPI property table @%pa\n",
>   		&gic_rdists->prop_table_pa);
> @@ -1948,10 +1963,27 @@ static void its_free_pending_table(struct page *pt)
>   	free_pages((unsigned long)page_address(pt), get_order(LPI_PENDBASE_SZ));
>   }
>   
> +static bool enabled_lpis_allowed(void)
> +{
> +	return false;
> +}
> +
>   static int __init allocate_lpi_tables(void)
>   {
> +	u64 val;
>   	int err, cpu;
>   
> +	/*
> +	 * If LPIs are enabled while we run this from the boot CPU,
> +	 * flag the RD tables as pre-allocated if the stars do align.
> +	 */
> +	val = readl_relaxed(gic_data_rdist_rd_base() + GICR_CTLR);
> +	if ((val & GICR_CTLR_ENABLE_LPIS) && enabled_lpis_allowed()) {
> +		gic_rdists->flags |= (RDIST_FLAGS_RD_TABLES_PREALLOCATED |
> +				      RDIST_FLAGS_PROPBASE_NEEDS_FLUSHING);
> +		pr_info("GICv3: Using preallocated redistributor tables\n");
> +	}
> +
>   	err = its_alloc_lpi_prop_table();
>   	if (err)
>   		return err;
> @@ -1986,6 +2018,18 @@ static void its_cpu_init_lpis(void)
>   	if (gic_data_rdist()->lpi_enabled)
>   		return;
>   
> +	val = readl_relaxed(rbase + GICR_CTLR);
> +	if ((gic_rdists->flags & RDIST_FLAGS_RD_TABLES_PREALLOCATED) &&
> +	    (val & GICR_CTLR_ENABLE_LPIS)) {
> +		paddr = gicr_read_pendbaser(rbase + GICR_PENDBASER);
> +		paddr &= GENMASK_ULL(51, 16);
> +
> +		its_free_pending_table(gic_data_rdist()->pend_page);
> +		gic_data_rdist()->pend_page = NULL;
> +
> +		goto out;
> +	}
> +
>   	pend_page = gic_data_rdist()->pend_page;
>   	paddr = page_to_phys(pend_page);
>   
> @@ -2040,9 +2084,11 @@ static void its_cpu_init_lpis(void)
>   
>   	/* Make sure the GIC has seen the above */
>   	dsb(sy);
> +out:
>   	gic_data_rdist()->lpi_enabled = true;
> -	pr_info("GICv3: CPU%d: using LPI pending table @%pa\n",
> +	pr_info("GICv3: CPU%d: using %s LPI pending table @%pa\n",
>   		smp_processor_id(),
> +		gic_data_rdist()->pend_page ? "allocated" : "reserved",
>   		&paddr);
>   }
>   
> @@ -3535,8 +3581,11 @@ static int redist_disable_lpis(void)
>   	 * If coming via a CPU hotplug event, we don't need to disable
>   	 * LPIs before trying to re-enable them. They are already
>   	 * configured and all is well in the world.
> +	 *
> +	 * If running with preallocated tables, there is nothing to do.
>   	 */
> -	if (gic_data_rdist()->lpi_enabled)
> +	if (gic_data_rdist()->lpi_enabled ||
> +	    (gic_rdists->flags & RDIST_FLAGS_RD_TABLES_PREALLOCATED))
>   		return 0;
>   
>   	/*
> 

-- 
Julien Thierry