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Date:   Wed, 26 Jan 2022 09:57:26 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
To:     Marc Zyngier <maz@kernel.org>
Cc:     linux-kernel@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
        kernel-team@android.com, Jay Chen <jkchen@linux.alibaba.com>
Subject: Re: [PATCH v3] irqchip/gic-v3-its: Reset each ITS's BASERn register
 before probe
Message-ID: <20220126095726.GA23794@lpieralisi>
References: <20220124133809.1291195-1-maz@kernel.org>
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On Mon, Jan 24, 2022 at 01:38:09PM +0000, Marc Zyngier wrote:
> A recent bug report outlined that the way GICv4.1 is handled across
> kexec is pretty bad. We can end-up in a situation where ITSs share
> memory (this is the case when SVPET==1) and reprogram the base
> registers, creating a situation where ITSs that are part of a given
> affinity group see different pointers. Which is illegal. Boo.
> 
> In order to restore some sanity, reset the BASERn registers to 0
> *before* probing any ITS. Although this isn't optimised at all,
> this is only a once-per-boot cost, which shouldn't show up on
> anyone's radar.
> 
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Cc: Jay Chen <jkchen@linux.alibaba.com>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> Link: https://lore.kernel.org/r/20211216190315.GA14220@lpieralisi
> ---
>  drivers/irqchip/irq-gic-v3-its.c | 114 +++++++++++++++++++++++++------
>  1 file changed, 93 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index 7b8f1ec0ff78..c09d99d5b637 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -4856,6 +4856,38 @@ static struct syscore_ops its_syscore_ops = {
>  	.resume = its_restore_enable,
>  };
>  
> +static void __init __iomem *its_map_one(struct resource *res, int *err)
> +{
> +	void __iomem *its_base;
> +	u32 val;
> +
> +	its_base = ioremap(res->start, SZ_64K);
> +	if (!its_base) {
> +		pr_warn("ITS@%pa: Unable to map ITS registers\n", &res->start);
> +		*err = -ENOMEM;
> +		return NULL;
> +	}
> +
> +	val = readl_relaxed(its_base + GITS_PIDR2) & GIC_PIDR2_ARCH_MASK;
> +	if (val != 0x30 && val != 0x40) {
> +		pr_warn("ITS@%pa: No ITS detected, giving up\n", &res->start);
> +		*err = -ENODEV;
> +		goto out_unmap;
> +	}
> +
> +	*err = its_force_quiescent(its_base);
> +	if (*err) {
> +		pr_warn("ITS@%pa: Failed to quiesce, giving up\n", &res->start);
> +		goto out_unmap;
> +	}
> +
> +	return its_base;
> +
> +out_unmap:
> +	iounmap(its_base);
> +	return NULL;
> +}
> +
>  static int its_init_domain(struct fwnode_handle *handle, struct its_node *its)
>  {
>  	struct irq_domain *inner_domain;
> @@ -4963,29 +4995,14 @@ static int __init its_probe_one(struct resource *res,
>  {
>  	struct its_node *its;
>  	void __iomem *its_base;
> -	u32 val, ctlr;
>  	u64 baser, tmp, typer;
>  	struct page *page;
> +	u32 ctlr;
>  	int err;
>  
> -	its_base = ioremap(res->start, SZ_64K);
> -	if (!its_base) {
> -		pr_warn("ITS@%pa: Unable to map ITS registers\n", &res->start);
> -		return -ENOMEM;
> -	}
> -
> -	val = readl_relaxed(its_base + GITS_PIDR2) & GIC_PIDR2_ARCH_MASK;
> -	if (val != 0x30 && val != 0x40) {
> -		pr_warn("ITS@%pa: No ITS detected, giving up\n", &res->start);
> -		err = -ENODEV;
> -		goto out_unmap;
> -	}
> -
> -	err = its_force_quiescent(its_base);
> -	if (err) {
> -		pr_warn("ITS@%pa: Failed to quiesce, giving up\n", &res->start);
> -		goto out_unmap;
> -	}
> +	its_base = its_map_one(res, &err);
> +	if (!its_base)
> +		return err;
>  
>  	pr_info("ITS %pR\n", res);
>  
> @@ -5249,6 +5266,23 @@ static int its_cpu_memreserve_lpi(unsigned int cpu)
>  	return ret;
>  }
>  
> +/* Mark all the BASER registers as invalid before they get reprogrammed */
> +static int __init its_reset_one(struct resource *res)
> +{
> +	void __iomem *its_base;
> +	int err, i;
> +
> +	its_base = its_map_one(res, &err);
> +	if (!its_base)
> +		return err;
> +
> +	for (i = 0; i < GITS_BASER_NR_REGS; i++)
> +		gits_write_baser(0, its_base + GITS_BASER + (i << 3));
> +
> +	iounmap(its_base);
> +	return 0;
> +}
> +
>  static const struct of_device_id its_device_id[] = {
>  	{	.compatible	= "arm,gic-v3-its",	},
>  	{},
> @@ -5259,6 +5293,26 @@ static int __init its_of_probe(struct device_node *node)
>  	struct device_node *np;
>  	struct resource res;
>  
> +	/*
> +	 * Make sure *all* the ITS are reset before we probe any, as
> +	 * they may be sharing memory. If any of the ITS fails to
> +	 * reset, don't even try to go any further, as this could
> +	 * result in something even worse.
> +	 */
> +	for (np = of_find_matching_node(node, its_device_id); np;
> +	     np = of_find_matching_node(np, its_device_id)) {
> +		int err;
> +
> +		if (!of_device_is_available(np) ||
> +		    !of_property_read_bool(np, "msi-controller") ||
> +		    of_address_to_resource(np, 0, &res))
> +			continue;
> +
> +		err = its_reset_one(&res);
> +		if (err)
> +			return err;
> +	}
> +
>  	for (np = of_find_matching_node(node, its_device_id); np;
>  	     np = of_find_matching_node(np, its_device_id)) {
>  		if (!of_device_is_available(np))
> @@ -5421,11 +5475,29 @@ static int __init gic_acpi_parse_madt_its(union acpi_subtable_headers *header,
>  	return err;
>  }
>  
> +static int __init its_acpi_reset(union acpi_subtable_headers *header,
> +				 const unsigned long end)
> +{
> +	struct acpi_madt_generic_translator *its_entry;
> +	struct resource res;
> +
> +	its_entry = (struct acpi_madt_generic_translator *)header;
> +	res = (struct resource) {
> +		.start	= its_entry->base_address,
> +		.end	= its_entry->base_address + ACPI_GICV3_ITS_MEM_SIZE - 1,
> +		.flags	= IORESOURCE_MEM,
> +	};
> +
> +	return its_reset_one(&res);
> +}
> +
>  static void __init its_acpi_probe(void)
>  {
>  	acpi_table_parse_srat_its();
> -	acpi_table_parse_madt(ACPI_MADT_TYPE_GENERIC_TRANSLATOR,
> -			      gic_acpi_parse_madt_its, 0);
> +	if (acpi_table_parse_madt(ACPI_MADT_TYPE_GENERIC_TRANSLATOR,
> +				  its_acpi_reset, 0) > 0)
> +		acpi_table_parse_madt(ACPI_MADT_TYPE_GENERIC_TRANSLATOR,
> +				      gic_acpi_parse_madt_its, 0);

Maybe it is worth adding a comment here as you did for DT if you
can before merging it - to clarify the first acpi_table_parse_madt()
call logic.

Other than that:

Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

>  	acpi_its_srat_maps_free();
>  }
>  #else
> -- 
> 2.34.1
>