Commit 8fcc4ae6 authored by James Morse's avatar James Morse Committed by Rafael J. Wysocki
Browse files

arm64: acpi: Make apei_claim_sea() synchronise with APEI's irq work 



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: default avatarJames Morse <james.morse@arm.com>
Tested-by: default avatarTyler Baicar <baicar@os.amperecomputing.com>
Acked-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 7f17b4a1

arch/arm64/kernel/acpi.c

+25 −0
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ 
#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>
@@ -269,6 +270,7 @@ 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))
@@ -276,6 +278,12 @@ int apei_claim_sea(struct pt_regs *regs) 


	current_flags = local_daif_save_flags();



	/* current_flags isn't useful here as daif doesn't tell us about pNMI */

	return_to_irqs_enabled = !irqs_disabled_flags(arch_local_save_flags());



	if (regs)

		return_to_irqs_enabled = interrupts_enabled(regs);



	/*

	 * SEA can interrupt SError, mask it and describe this as an NMI so

	 * that APEI defers the handling.
@@ -284,6 +292,23 @@ 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_ratelimited("APEI work queued but not completed");

			err = -EINPROGRESS;

		}

	}



	local_daif_restore(current_flags);



	return err;

arch/arm64/mm/fault.c

+7 −5
Original line number Diff line number Diff line
@@ -635,11 +635,13 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs) 


	inf = esr_to_fault_info(esr);



	if (user_mode(regs) && apei_claim_sea(regs) == 0) {

		/*

	 * Return value ignored as we rely on signal merging.

	 * Future patches will make this more robust.

		 * APEI claimed this as a firmware-first notification.

		 * Some processing deferred to task_work before ret_to_user().

		 */

	apei_claim_sea(regs);

		return 0;

	}



	if (esr & ESR_ELx_FnV)

		siaddr = NULL;

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