On 22/03/18 18:14, James Morse wrote:
> To ensure APEI always takes the same locks when processing a notification
> we need the nmi-like callers to always call APEI 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. We can then go on to see if (a future)
> kernel-first mechanism wants to claim the notification, before
> falling through to the existing default behaviour.
>
> The NOTIFY_SEA code was merged before we had multiple, possibly
> interacting, NMI-like notifications and the need to consider kernel
> first in the future. Make the 'claiming' behaviour explicit.
>
> As we're restructuring the APEI code to allow multiple NMI-like
> notifications, any notification that might interrupt interrupts-masked
> code must always be wrapped in nmi_enter()/nmi_exit(). This allows APEI
> to use in_nmi() to choose between the raw/regular spinlock routines.
>
> We 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>
> ---
> 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. See patch 11.
>
> Changes since v1:
> * Tinkered with the commit message
>
> arch/arm64/include/asm/acpi.h | 3 +++
> arch/arm64/include/asm/daifflags.h | 1 +
> arch/arm64/include/asm/kvm_ras.h | 20 +++++++++++++++++++-
> arch/arm64/kernel/acpi.c | 30 ++++++++++++++++++++++++++++++
> arch/arm64/mm/fault.c | 31 +++++++------------------------
> 5 files changed, 60 insertions(+), 25 deletions(-)
>
> diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
> index 32f465a80e4e..256811cd4b8b 100644
> --- a/arch/arm64/include/asm/acpi.h
> +++ b/arch/arm64/include/asm/acpi.h
> @@ -16,6 +16,7 @@
> #include <linux/psci.h>
>
> #include <asm/cputype.h>
> +#include <asm/ptrace.h>
> #include <asm/smp_plat.h>
> #include <asm/tlbflush.h>
>
> @@ -94,6 +95,8 @@ void __init acpi_init_cpus(void);
> static inline void acpi_init_cpus(void) { }
> #endif /* CONFIG_ACPI */
>
> +int apei_claim_sea(struct pt_regs *regs);
> +
> #ifdef CONFIG_ARM64_ACPI_PARKING_PROTOCOL
> bool acpi_parking_protocol_valid(int cpu);
> void __init
> diff --git a/arch/arm64/include/asm/daifflags.h b/arch/arm64/include/asm/daifflags.h
> index 22e4c83de5a5..cbd753855bf3 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 5f72b07b7912..9d52bc333110 100644
> --- a/arch/arm64/include/asm/kvm_ras.h
> +++ b/arch/arm64/include/asm/kvm_ras.h
> @@ -4,8 +4,26 @@
> #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.
> + *
> + * Call with irqs unmaksed.
> + */
> +static inline int kvm_handle_guest_sea(phys_addr_t addr, unsigned int esr)
> +{
> + int ret = -ENOENT;
> +
> + if (IS_ENABLED(CONFIG_ACPI_APEI_SEA))
> + ret = apei_claim_sea(NULL);
Nit: it is a bit odd to see this "IS_ENABLED(CONFIG_ACPI_APEI_SEA)"
check both in this function and in the only other function this calls
(apei_claim_sea). Could this somehow be improved by having a dummy
apei_claim_sea if CONFIG_ACPI_APEI doesn't exist?
> +
> + return ret;
> +}
>
> #endif /* __ARM64_KVM_RAS_H__ */
> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> index 7b09487ff8fb..6a4823a3eb5e 100644
> --- a/arch/arm64/kernel/acpi.c
> +++ b/arch/arm64/kernel/acpi.c
> @@ -33,6 +33,8 @@
>
> #ifdef CONFIG_ACPI_APEI
> # include <linux/efi.h>
> +# include <acpi/ghes.h>
> +# include <asm/daifflags.h>
> # include <asm/pgtable.h>
> #endif
>
> @@ -261,4 +263,32 @@ pgprot_t arch_apei_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 = arch_local_save_flags();
> +
> + if (!IS_ENABLED(CONFIG_ACPI_APEI_SEA))
> + return err;
> +
> + /*
> + * APEI expects an NMI-like notification to always be called
> + * in NMI context.
> + */
> + local_daif_restore(DAIF_ERRCTX);
> + nmi_enter();
> + err = ghes_notify_sea();
> + nmi_exit();
> + local_daif_restore(current_flags);
> +
> + return err;
> +}
> #endif
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index adac28ce9be3..303c8b425c82 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>
> @@ -44,8 +46,6 @@
> #include <asm/pgtable.h>
> #include <asm/tlbflush.h>
>
> -#include <acpi/ghes.h>
> -
> struct fault_info {
> int (*fn)(unsigned long addr, unsigned int esr,
> struct pt_regs *regs);
> @@ -579,19 +579,12 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs)
> pr_err("Synchronous External Abort: %s (0x%08x) at 0x%016lx\n",
> inf->name, esr, addr);
>
> - /*
> - * Synchronous aborts may interrupt code which had interrupts masked.
> - * Before calling out into the wider kernel tell the interested
> - * subsystems.
> - */
> if (IS_ENABLED(CONFIG_ACPI_APEI_SEA)) {
> - if (interrupts_enabled(regs))
> - nmi_enter();
> -
> - ghes_notify_sea();
> -
> - if (interrupts_enabled(regs))
> - nmi_exit();
> + /*
> + * Return value ignored as we rely on signal merging.
> + * Future patches will make this more robust.
> + */
> + apei_claim_sea(regs);
> }
>
> info.si_signo = SIGBUS;
> @@ -673,16 +666,6 @@ static const struct fault_info fault_info[] = {
> { do_bad, SIGBUS, BUS_FIXME, "unknown 63" },
> };
>
> -int kvm_handle_guest_sea(phys_addr_t addr, unsigned int esr)
> -{
> - int ret = -ENOENT;
> -
> - if (IS_ENABLED(CONFIG_ACPI_APEI_SEA))
> - ret = ghes_notify_sea();
> -
> - return ret;
> -}
> -
> asmlinkage void __exception do_mem_abort(unsigned long addr, unsigned int esr,
> struct pt_regs *regs)
> {
>
Otherwise:
Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx>
M.
--
Jazz is not dead. It just smells funny...
