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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: James Morse <james.morse@arm.com>
Tested-by: Tyler Baicar <baicar@os.amperecomputing.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
James Morse 2020-05-01 17:45:43 +01:00 committed by Rafael J. Wysocki
parent 7f17b4a121
commit 8fcc4ae6fa
2 changed files with 32 additions and 5 deletions
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25
arch/arm64/kernel/acpi.c
View File

@ -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;

12
arch/arm64/mm/fault.c
View File

@ -635,11 +635,13 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs)
inf = esr_to_fault_info(esr);
/*
* Return value ignored as we rely on signal merging.
* Future patches will make this more robust.
*/
apei_claim_sea(regs);
if (user_mode(regs) && apei_claim_sea(regs) == 0) {
/*
* APEI claimed this as a firmware-first notification.
* Some processing deferred to task_work before ret_to_user().
*/
return 0;
}
if (esr & ESR_ELx_FnV)
siaddr = NULL;