To split up APEIs in_nmi() path, the caller needs to always be
in_nmi(). Add a helper to do the work and claim the notification.
When KVM or the arch code takes an exception that might be a RAS
notification, it asks the APEI firmware-first code whether it wants
to claim the exception. A future kernel-first mechanism may be queried
afterwards, and claim the notification, otherwise we fall through
to the existing default behaviour.
The NOTIFY_SEA code was merged before considering multiple, possibly
interacting, NMI-like notifications and the need to consider kernel
first in the future. Make the 'claiming' behaviour explicit.
Restructuring the APEI code to allow multiple NMI-like notifications
means any notification that might interrupt interrupts-masked
code must always be wrapped in nmi_enter()/nmi_exit(). This will
allow APEI to use in_nmi() to use the right fixmap entries.
Mask SError over this window to prevent an asynchronous RAS error
arriving and tripping 'nmi_enter()'s BUG_ON(in_nmi()).
Signed-off-by: James Morse <james.morse@xxxxxxx>
Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Tested-by: Tyler Baicar <tbaicar@xxxxxxxxxxxxxx>
---
Why does apei_claim_sea() take a pt_regs? This gets used later to take
APEI by the hand through NMI->IRQ context, depending on what we
interrupted.
Changes since v6:
* Moved the voice of the commit message.
* moved arch_local_save_flags() below the !IS_ENABLED drop-out
* Moved the dummy declaration into the if-ACPI part of the header instead
of if-APEI.
Changes since v4:
* Made irqs-unmasked comment a lockdep assert.
Changes since v3:
* Removed spurious whitespace change
* Updated comment in acpi.c to cover SError masking
Changes since v2:
* Added dummy definition for !ACPI and culled IS_ENABLED() checks.
---
arch/arm64/include/asm/acpi.h | 4 +++-
arch/arm64/include/asm/daifflags.h | 1 +
arch/arm64/include/asm/kvm_ras.h | 16 ++++++++++++++-
arch/arm64/kernel/acpi.c | 31 ++++++++++++++++++++++++++++++
arch/arm64/mm/fault.c | 24 +++++------------------
5 files changed, 55 insertions(+), 21 deletions(-)
diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
index 709208dfdc8b..4ed19b26ec1a 100644
--- a/arch/arm64/include/asm/acpi.h
+++ b/arch/arm64/include/asm/acpi.h
@@ -18,6 +18,7 @@
#include <asm/cputype.h>
#include <asm/io.h>
+#include <asm/ptrace.h>
#include <asm/smp_plat.h>
#include <asm/tlbflush.h>
@@ -99,9 +100,10 @@ static inline u32 get_acpi_id_for_cpu(unsigned int cpu)
static inline void arch_fix_phys_package_id(int num, u32 slot) { }
void __init acpi_init_cpus(void);
-
+int apei_claim_sea(struct pt_regs *regs);
#else
static inline void acpi_init_cpus(void) { }
+static inline int apei_claim_sea(struct pt_regs *regs) { return -ENOENT; }
#endif /* CONFIG_ACPI */
#ifdef CONFIG_ARM64_ACPI_PARKING_PROTOCOL
diff --git a/arch/arm64/include/asm/daifflags.h b/arch/arm64/include/asm/daifflags.h
index 8d91f2233135..fa90779fc752 100644
--- a/arch/arm64/include/asm/daifflags.h
+++ b/arch/arm64/include/asm/daifflags.h
@@ -20,6 +20,7 @@
#define DAIF_PROCCTX 0
#define DAIF_PROCCTX_NOIRQ PSR_I_BIT
+#define DAIF_ERRCTX (PSR_I_BIT | PSR_A_BIT)
/* mask/save/unmask/restore all exceptions, including interrupts. */
static inline void local_daif_mask(void)
diff --git a/arch/arm64/include/asm/kvm_ras.h b/arch/arm64/include/asm/kvm_ras.h
index 6096f0251812..8ac6ee77437c 100644
--- a/arch/arm64/include/asm/kvm_ras.h
+++ b/arch/arm64/include/asm/kvm_ras.h
@@ -4,8 +4,22 @@
#ifndef __ARM64_KVM_RAS_H__
#define __ARM64_KVM_RAS_H__
+#include <linux/acpi.h>
+#include <linux/errno.h>
#include <linux/types.h>
-int kvm_handle_guest_sea(phys_addr_t addr, unsigned int esr);
+#include <asm/acpi.h>
+
+/*
+ * Was this synchronous external abort a RAS notification?
+ * Returns '0' for errors handled by some RAS subsystem, or -ENOENT.
+ */
+static inline int kvm_handle_guest_sea(phys_addr_t addr, unsigned int esr)
+{
+ /* apei_claim_sea(NULL) expects to mask interrupts itself */
+ lockdep_assert_irqs_enabled();
+
+ return apei_claim_sea(NULL);
+}
#endif /* __ARM64_KVM_RAS_H__ */
diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
index 44e3c351e1ea..803f0494dd3e 100644
--- a/arch/arm64/kernel/acpi.c
+++ b/arch/arm64/kernel/acpi.c
@@ -27,8 +27,10 @@
#include <linux/smp.h>
#include <linux/serial_core.h>
+#include <acpi/ghes.h>
#include <asm/cputype.h>
#include <asm/cpu_ops.h>
+#include <asm/daifflags.h>
#include <asm/pgtable.h>
#include <asm/smp_plat.h>
@@ -256,3 +258,32 @@ pgprot_t __acpi_get_mem_attribute(phys_addr_t addr)
return __pgprot(PROT_NORMAL_NC);
return __pgprot(PROT_DEVICE_nGnRnE);
}
+
+/*
+ * Claim Synchronous External Aborts as a firmware first notification.
+ *
+ * Used by KVM and the arch do_sea handler.
+ * @regs may be NULL when called from process context.
+ */
+int apei_claim_sea(struct pt_regs *regs)
+{
+ int err = -ENOENT;
+ unsigned long current_flags;
+
+ if (!IS_ENABLED(CONFIG_ACPI_APEI_GHES))
+ return err;
+
+ current_flags = arch_local_save_flags();
+
+ /*
+ * SEA can interrupt SError, mask it and describe this as an NMI so
+ * that APEI defers the handling.
+ */
+ local_daif_restore(DAIF_ERRCTX);
+ nmi_enter();
+ err = ghes_notify_sea();
+ nmi_exit();
+ local_daif_restore(current_flags);
+
+ return err;
+}
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index eeeb576b33d7..956afc7d932a 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -18,6 +18,7 @@
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
+#include <linux/acpi.h>
#include <linux/extable.h>
#include <linux/signal.h>
#include <linux/mm.h>
@@ -33,6 +34,7 @@
#include <linux/preempt.h>
#include <linux/hugetlb.h>
+#include <asm/acpi.h>
#include <asm/bug.h>
#include <asm/cmpxchg.h>
#include <asm/cpufeature.h>
@@ -46,8 +48,6 @@
#include <asm/tlbflush.h>
#include <asm/traps.h>
-#include <acpi/ghes.h>
-
struct fault_info {
int (*fn)(unsigned long addr, unsigned int esr,
struct pt_regs *regs);
@@ -630,19 +630,10 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs)
inf = esr_to_fault_info(esr);
/*
- * Synchronous aborts may interrupt code which had interrupts masked.
- * Before calling out into the wider kernel tell the interested
- * subsystems.
+ * Return value ignored as we rely on signal merging.
+ * Future patches will make this more robust.
*/
- if (IS_ENABLED(CONFIG_ACPI_APEI_SEA)) {
- if (interrupts_enabled(regs))
- nmi_enter();
-
- ghes_notify_sea();
-
- if (interrupts_enabled(regs))
- nmi_exit();
- }
+ apei_claim_sea(regs);
if (esr & ESR_ELx_FnV)
siaddr = NULL;
@@ -720,11 +711,6 @@ static const struct fault_info fault_info[] = {
{ do_bad, SIGKILL, SI_KERNEL, "unknown 63" },
};
-int kvm_handle_guest_sea(phys_addr_t addr, unsigned int esr)
-{
- return ghes_notify_sea();
-}
-
asmlinkage void __exception do_mem_abort(unsigned long addr, unsigned int esr,
struct pt_regs *regs)
{
--
2.19.2
