Hi James,
On 29/01/2019 18:49, James Morse wrote:
> APEI is unable to do all of its error handling work in nmi-context, so
> it defers non-fatal work onto the irq_work queue. arch_irq_work_raise()
> sends an IPI to the calling cpu, but this is not guaranteed to be taken
> before returning to user-space.
>
> Unless the exception interrupted a context with irqs-masked,
> irq_work_run() can run immediately. Otherwise return -EINPROGRESS to
> indicate ghes_notify_sea() found some work to do, but it hasn't
> finished yet.
>
> With this apei_claim_sea() returning '0' means this external-abort was
> also notification of a firmware-first RAS error, and that APEI has
> processed the CPER records.
>
> Signed-off-by: James Morse <james.morse@xxxxxxx>
> Reviewed-by: Punit Agrawal <punit.agrawal@xxxxxxx>
> Tested-by: Tyler Baicar <tbaicar@xxxxxxxxxxxxxx>
> Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> CC: Xie XiuQi <xiexiuqi@xxxxxxxxxx>
> CC: gengdongjiu <gengdongjiu@xxxxxxxxxx>
>
> ---
> Changes since v7:
> * Added Catalin's ack, then:
> * Added __irq_enter()/exit() calls so if we interrupted preemptible code, the
> preempt count matches what other irq-work expects.
> * Changed the 'if (!arch_irqs_disabled_flags(interrupted_flags))' test to be
> safe before/after Julien's PMR series.
>
> Changes since v6:
> * Added pr_warn() for the EINPROGRESS case so panic-tracebacks show
> 'APEI was here'.
> * Tinkered with the commit message
>
> Changes since v2:
> * Removed IS_ENABLED() check, done by the caller unless we have a dummy
> definition.
> ---
> arch/arm64/kernel/acpi.c | 23 +++++++++++++++++++++++
> arch/arm64/mm/fault.c | 9 ++++-----
> 2 files changed, 27 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> index 803f0494dd3e..8288ae0c8f3b 100644
> --- a/arch/arm64/kernel/acpi.c
> +++ b/arch/arm64/kernel/acpi.c
> @@ -22,6 +22,7 @@
> #include <linux/init.h>
> #include <linux/irq.h>
> #include <linux/irqdomain.h>
> +#include <linux/irq_work.h>
> #include <linux/memblock.h>
> #include <linux/of_fdt.h>
> #include <linux/smp.h>
> @@ -268,12 +269,17 @@ pgprot_t __acpi_get_mem_attribute(phys_addr_t addr)
> int apei_claim_sea(struct pt_regs *regs)
> {
> int err = -ENOENT;
> + bool return_to_irqs_enabled;
> unsigned long current_flags;
>
> if (!IS_ENABLED(CONFIG_ACPI_APEI_GHES))
> return err;
>
> current_flags = arch_local_save_flags();
> + return_to_irqs_enabled = !irqs_disabled_flags(current_flags);
> +
> + if (regs)
> + return_to_irqs_enabled = interrupts_enabled(regs);
>
> /*
> * SEA can interrupt SError, mask it and describe this as an NMI so
> @@ -283,6 +289,23 @@ int apei_claim_sea(struct pt_regs *regs)
> nmi_enter();
> err = ghes_notify_sea();
> nmi_exit();
> +
> + /*
> + * APEI NMI-like notifications are deferred to irq_work. Unless
> + * we interrupted irqs-masked code, we can do that now.
> + */
> + if (!err) {
> + if (return_to_irqs_enabled) {
> + local_daif_restore(DAIF_PROCCTX_NOIRQ);
> + __irq_enter();
> + irq_work_run();
> + __irq_exit();
> + } else {
> + pr_warn("APEI work queued but not completed");
> + err = -EINPROGRESS;
> + }
> + }
> +
Reviewed-by: Julien Thierry <julien.thierry@xxxxxxx>
Cheers,
--
Julien Thierry
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