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Date: Mon, 24 Sep 2018 12:58:09 +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 04/10] irqchip/gic-v3-its: Move pending table allocation
to init time
Hi Marc,
On 21/09/18 20:59, Marc Zyngier wrote:
> Pending tables for the redistributors are currently allocated
> one at a time as each CPU boots. This is causing some grief
> for Linux/RT (allocation from within a CPU hotplug notifier is
> frown upon).
>
> Let's more this allocation to take place at init time, when we
> only have a single CPU. It means we're allocating memory for CPUs
> that are not online yet, but most system will boot all of their
> CPUs anyway, so that's not completely wasted.
>
> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> ---
> drivers/irqchip/irq-gic-v3-its.c | 80 +++++++++++++++++++-----------
> include/linux/irqchip/arm-gic-v3.h | 1 +
> 2 files changed, 53 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index 7ef6baea2d78..462bba422189 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -173,6 +173,7 @@ static DEFINE_RAW_SPINLOCK(vmovp_lock);
> static DEFINE_IDA(its_vpeid_ida);
>
> #define gic_data_rdist() (raw_cpu_ptr(gic_rdists->rdist))
> +#define gic_data_rdist_cpu(cpu) (per_cpu_ptr(gic_rdists->rdist, cpu))
> #define gic_data_rdist_rd_base() (gic_data_rdist()->rd_base)
> #define gic_data_rdist_vlpi_base() (gic_data_rdist_rd_base() + SZ_128K)
>
> @@ -1625,7 +1626,7 @@ static void its_free_prop_table(struct page *prop_page)
> get_order(LPI_PROPBASE_SZ));
> }
>
> -static int __init its_alloc_lpi_tables(void)
> +static int __init its_alloc_lpi_prop_table(void)
A bit of a nit, but there is already a function called
"its_allocate_prop_table" which I find very easy to confuse with this one.
And patch 3 factored the initialization out of its_allocate_prop_table.
So I was wondering whether it would not actually be better to open-code
it here and get rid of that function. Otherwise I'd suggest having more
distinct names.
Otherwise the patch looks good.
Thanks,
> {
> phys_addr_t paddr;
>
> @@ -1944,30 +1945,47 @@ static void its_free_pending_table(struct page *pt)
> free_pages((unsigned long)page_address(pt), get_order(LPI_PENDBASE_SZ));
> }
>
> -static void its_cpu_init_lpis(void)
> +static int __init allocate_lpi_tables(void)
> {
> - void __iomem *rbase = gic_data_rdist_rd_base();
> - struct page *pend_page;
> - u64 val, tmp;
> + int err, cpu;
>
> - /* If we didn't allocate the pending table yet, do it now */
> - pend_page = gic_data_rdist()->pend_page;
> - if (!pend_page) {
> - phys_addr_t paddr;
> + err = its_alloc_lpi_prop_table();
> + if (err)
> + return err;
> +
> + /*
> + * We allocate all the pending tables anyway, as we may have a
> + * mix of RDs that have had LPIs enabled, and some that
> + * don't. We'll free the unused ones as each CPU comes online.
> + */
> + for_each_possible_cpu(cpu) {
> + struct page *pend_page;
>
> pend_page = its_allocate_pending_table(GFP_NOWAIT);
> if (!pend_page) {
> - pr_err("Failed to allocate PENDBASE for CPU%d\n",
> - smp_processor_id());
> - return;
> + pr_err("Failed to allocate PENDBASE for CPU%d\n", cpu);
> + return -ENOMEM;
> }
>
> - paddr = page_to_phys(pend_page);
> - pr_info("CPU%d: using LPI pending table @%pa\n",
> - smp_processor_id(), &paddr);
> - gic_data_rdist()->pend_page = pend_page;
> + gic_data_rdist_cpu(cpu)->pend_page = pend_page;
> }
>
> + return 0;
> +}
> +
> +static void its_cpu_init_lpis(void)
> +{
> + void __iomem *rbase = gic_data_rdist_rd_base();
> + struct page *pend_page;
> + phys_addr_t paddr;
> + u64 val, tmp;
> +
> + if (gic_data_rdist()->lpi_enabled)
> + return;
> +
> + pend_page = gic_data_rdist()->pend_page;
> + paddr = page_to_phys(pend_page);
> +
> /* set PROPBASE */
> val = (page_to_phys(gic_rdists->prop_page) |
> GICR_PROPBASER_InnerShareable |
> @@ -2019,6 +2037,10 @@ static void its_cpu_init_lpis(void)
>
> /* Make sure the GIC has seen the above */
> dsb(sy);
> + gic_data_rdist()->lpi_enabled = true;
> + pr_info("GICv3: CPU%d: using LPI pending table @%pa\n",
> + smp_processor_id(),
> + &paddr);
> }
>
> static void its_cpu_init_collection(struct its_node *its)
> @@ -3497,16 +3519,6 @@ static int redist_disable_lpis(void)
> u64 timeout = USEC_PER_SEC;
> u64 val;
>
> - /*
> - * 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. Detect this case
> - * by checking the allocation of the pending table for the
> - * current CPU.
> - */
> - if (gic_data_rdist()->pend_page)
> - return 0;
> -
> if (!gic_rdists_supports_plpis()) {
> pr_info("CPU%d: LPIs not supported\n", smp_processor_id());
> return -ENXIO;
> @@ -3516,7 +3528,18 @@ static int redist_disable_lpis(void)
> if (!(val & GICR_CTLR_ENABLE_LPIS))
> return 0;
>
> - pr_warn("CPU%d: Booted with LPIs enabled, memory probably corrupted\n",
> + /*
> + * 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 (gic_data_rdist()->lpi_enabled)
> + return 0;
> +
> + /*
> + * From that point on, we only try to do some damage control.
> + */
> + pr_warn("GICv3: CPU%d: Booted with LPIs enabled, memory probably corrupted\n",
> smp_processor_id());
> add_taint(TAINT_CRAP, LOCKDEP_STILL_OK);
>
> @@ -3772,7 +3795,8 @@ int __init its_init(struct fwnode_handle *handle, struct rdists *rdists,
> }
>
> gic_rdists = rdists;
> - err = its_alloc_lpi_tables();
> +
> + err = allocate_lpi_tables();
> if (err)
> return err;
>
> diff --git a/include/linux/irqchip/arm-gic-v3.h b/include/linux/irqchip/arm-gic-v3.h
> index 8bdbb5f29494..266093e845bb 100644
> --- a/include/linux/irqchip/arm-gic-v3.h
> +++ b/include/linux/irqchip/arm-gic-v3.h
> @@ -585,6 +585,7 @@ struct rdists {
> void __iomem *rd_base;
> struct page *pend_page;
> phys_addr_t phys_base;
> + bool lpi_enabled;
> } __percpu *rdist;
> struct page *prop_page;
> u64 flags;
>
--
Julien Thierry
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