[PATCH 00/24] alpha: catch up on architecture Kconfig options

[PATCH 00/24] alpha: catch up on architecture Kconfig options

[Matt Turner]

Alpha is missing a long list of Kconfig options that other architectures
have picked up over the years, some of them for no better reason than
nobody having gone through the list.  I diffed the select statements in
every other arch/*/Kconfig against arch/alpha/Kconfig and worked through
what turned up.  This series is the result: two fixes it depends on, and
the options that are either free or close to it.

The patches are ordered from least to most contentious, so the front of
the series can be applied on its own if the tail needs discussion.

Patches 1-2 are fixes.  arch_irqs_disabled_flags() only reported
interrupts as disabled at IPL_MAX, but PALcode enters handlers at the
IPL of the interrupt being delivered, so a device or timer handler
answered that interrupts were enabled.  handle_irq() also called
irq_to_desc() before irq_enter(), running generic code with the preempt
count still saying task context and RCU not yet watching.  Both matter on
their own; patches 23 and 24 are what made them visible.

Patches 3-11 are one-line selects with no Alpha code behind them:
instrumentation (UBSAN, gcov, kmemleak), EDAC, and four properties Alpha
has always had but never declared (LL/SC atomics, hardware multiply,
__int128, the existing asm/compiler.h, and the non-overlapping user and
kernel address spaces).

Patches 12-17 add a small amount of code: an empty thread_struct
whitelist, _PAGE_SPECIAL on a free PTE bit, the page table check helpers,
and then the three things that follow from those - the page table helper
self test, lockless GUP, and the early memtest.  Note that early_memtest()
is called from arch_mm_preinit() rather than paging_init(), because Alpha
calls paging_init() from setup_arch(), before parse_early_param() has seen
the memtest= option.

Patches 18-20 change something visible.  Unhandled user faults now print
the usual message under the debug.exception-trace sysctl.  .eh_frame is
discarded: gcc emits it for Alpha regardless of
-fno-asynchronous-unwind-tables, it was allocated in the loaded image, and
nothing consumes it, since the stack trace code scans for text addresses
rather than unwinding DWARF.  That is worth about 1.1MB.  With that and
the relocation sections placed explicitly, the kernel links with no
orphans left, so the last of the three asks the linker to say so.

Patches 21-24 are the ones I expect to draw comment.  Patch 22 adds a
uapi header, so the perf register numbering is an ABI decision.  Patch 23
is SPARSE_IRQ: without it Marvel carries a 12.6MB static irq_desc[] in
.data for 32768 possible interrupts, of which a real ES47 uses 87, and
the kernel links at a fixed address just above the console reservation
where that 12.6MB is the difference between fitting and not.  Patch 24
instruments the entry assembly for lockdep hardirq tracking.

Tested with gcc 17 under QEMU (-M clipper -smp 2, an ALPHA_GENERIC build)
with PROVE_LOCKING enabled: no splats, early_memtest passes all four
patterns over the free memblock ranges with nothing reserved,
debug_vm_pgtable validates with no warning, a vmsplice() of an anonymous
mapping through pin_user_pages_fast() returns the right data, and an
unhandled SIGSEGV prints the new trace line.  Patch 23 was tested on an
AlphaServer ES47.

Not included, and worth mentioning: ARCH_HAS_KCOV.  A kernel with
KCOV_INSTRUMENT_ALL boots and runs, but CONFIG_KCOV_SELFTEST panics.  The
self test deliberately arms kcov with no coverage area so that any
instrumented function reached from interrupt context faults, checking
that nothing escapes the window before the preempt count says hardirq.
On Alpha something does.  Patch 2 fixes one such site; the panic survives
it, so the entry paths need an audit first.

Also available at:

  git://git.kernel.org/pub/scm/linux/kernel/git/mattst88/alpha.git arch-kconfig-options

Matt Turner (24):
  alpha: fix arch_irqs_disabled_flags() to treat any raised IPL as
    disabled
  alpha: enter hardirq context before looking up the irq descriptor
  alpha: select ARCH_HAS_UBSAN
  alpha: select ARCH_HAS_GCOV_PROFILE_ALL
  alpha: select HAVE_DEBUG_KMEMLEAK
  alpha: select EDAC_SUPPORT
  alpha: select ARCH_SUPPORTS_ATOMIC_RMW
  alpha: select ARCH_HAS_FAST_MULTIPLIER
  alpha: select ARCH_SUPPORTS_INT128
  alpha: select HAVE_ARCH_COMPILER_H
  alpha: select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
  alpha: add HAVE_ARCH_THREAD_STRUCT_WHITELIST support
  alpha: add ARCH_HAS_PTE_SPECIAL support
  alpha: add ARCH_SUPPORTS_PAGE_TABLE_CHECK support
  alpha: select ARCH_HAS_DEBUG_VM_PGTABLE
  alpha: select HAVE_GUP_FAST
  alpha: select ARCH_USE_MEMTEST
  alpha: select SYSCTL_EXCEPTION_TRACE
  alpha: discard .eh_frame and the relocation sections
  alpha: select ARCH_WANT_LD_ORPHAN_WARN
  alpha: select ARCH_WANT_IRQS_OFF_ACTIVATE_MM
  alpha: add HAVE_PERF_REGS and HAVE_PERF_USER_STACK_DUMP support
  alpha: select SPARSE_IRQ
  alpha: add TRACE_IRQFLAGS_SUPPORT

 arch/alpha/Kconfig                      | 21 ++++++
 arch/alpha/include/asm/irqflags.h       |  2 +-
 arch/alpha/include/asm/perf_regs.h      |  7 ++
 arch/alpha/include/asm/pgtable.h        | 21 +++++-
 arch/alpha/include/asm/processor.h      |  7 ++
 arch/alpha/include/uapi/asm/perf_regs.h | 34 ++++++++++
 arch/alpha/kernel/Makefile              |  1 +
 arch/alpha/kernel/entry.S               | 54 +++++++++++++Matt Turner (24):
  alpha: fix arch_irqs_disabled_flags() to treat any raised IPL as
    disabled
  alpha: enter hardirq context before looking up the irq descriptor
  alpha: select ARCH_HAS_UBSAN
  alpha: select ARCH_HAS_GCOV_PROFILE_ALL
  alpha: select HAVE_DEBUG_KMEMLEAK
  alpha: select EDAC_SUPPORT
  alpha: select ARCH_SUPPORTS_ATOMIC_RMW
  alpha: select ARCH_HAS_FAST_MULTIPLIER
  alpha: select ARCH_SUPPORTS_INT128
  alpha: select HAVE_ARCH_COMPILER_H
  alpha: select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
  alpha: add HAVE_ARCH_THREAD_STRUCT_WHITELIST support
  alpha: add ARCH_HAS_PTE_SPECIAL support
  alpha: add ARCH_SUPPORTS_PAGE_TABLE_CHECK support
  alpha: select ARCH_HAS_DEBUG_VM_PGTABLE
  alpha: select HAVE_GUP_FAST
  alpha: select ARCH_USE_MEMTEST
  alpha: select SYSCTL_EXCEPTION_TRACE
  alpha: discard .eh_frame and the relocation sections
  alpha: select ARCH_WANT_LD_ORPHAN_WARN
  alpha: select ARCH_WANT_IRQS_OFF_ACTIVATE_MM
  alpha: add HAVE_PERF_REGS and HAVE_PERF_USER_STACK_DUMP support
  alpha: select SPARSE_IRQ
  alpha: add TRACE_IRQFLAGS_SUPPORT

 arch/alpha/Kconfig                      | 21 ++++++
 arch/alpha/include/asm/irqflags.h       |  2 +-
 arch/alpha/include/asm/perf_regs.h      |  7 ++
 arch/alpha/include/asm/pgtable.h        | 21 +++++-
 arch/alpha/include/asm/processor.h      |  7 ++
 arch/alpha/include/uapi/asm/perf_regs.h | 34 ++++++++++
 arch/alpha/kernel/Makefile              |  1 +
 arch/alpha/kernel/entry.S               | 54 +++++++++++++---
 arch/alpha/kernel/irq.c                 |  9 ++-
 arch/alpha/kernel/irq_alpha.c           | 13 ++++
 arch/alpha/kernel/perf_regs.c           | 86 +++++++++++++++++++++++++
 arch/alpha/kernel/vmlinux.lds.S         | 11 ++++
 arch/alpha/mm/fault.c                   | 29 +++++++++
 arch/alpha/mm/init.c                    |  5 ++
 14 files changed, 287 insertions(+), 13 deletions(-)
 create mode 100644 arch/alpha/include/asm/perf_regs.h
 create mode 100644 arch/alpha/include/uapi/asm/perf_regs.h
 create mode 100644 arch/alpha/kernel/perf_regs.c

-- 
2.54.0

[PATCH 01/24] alpha: fix arch_irqs_disabled_flags() to treat any raised IPL as disabled

[Matt Turner]

arch_irqs_disabled_flags() only reported interrupts as disabled at
IPL_MAX, but the kernel is not the only thing that sets the IPL.  PALcode
raises PS.IPL to the level of the interrupt being delivered before
entering the handler, so a handler entered for a device interrupt runs at
IPL_DEV0 or IPL_DEV1, and the timer at IPL_TIMER.  Interrupts at and
below that level are blocked, but arch_irqs_disabled() answered that
interrupts were enabled.

Treat any IPL above IPL_MIN, the level arch_local_irq_enable() restores,
as interrupts disabled.  This matters as soon as lockdep is asked to
track hardirq state, where irqs_disabled() is expected to be true inside
an interrupt handler.

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/include/asm/irqflags.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git ./arch/alpha/include/asm/irqflags.h ./arch/alpha/include/asm/irqflags.h
index f207544f52de..ebbf5801f7a5 100644
--- ./arch/alpha/include/asm/irqflags.h
+++ ./arch/alpha/include/asm/irqflags.h
@@ -57,7 +57,7 @@ static inline void arch_local_irq_restore(unsigned long flags)
 
 static inline bool arch_irqs_disabled_flags(unsigned long flags)
 {
-	return (flags & 7) == IPL_MAX;
+	return (flags & 7) > IPL_MIN;
 }
 
 static inline bool arch_irqs_disabled(void)
-- 
2.54.0

Re: [PATCH 01/24] alpha: fix arch_irqs_disabled_flags() to treat any raised IPL as disabled

[Magnus Lindholm]

Hi, Matt

On Tue, Sep 1, 2026 at 5:50 PM Matt Turner <mattst88@gmail.com> wrote:
>
> arch_irqs_disabled_flags() only reported interrupts as disabled at
> IPL_MAX, but the kernel is not the only thing that sets the IPL.  PALcode
> raises PS.IPL to the level of the interrupt being delivered before
> entering the handler, so a handler entered for a device interrupt runs at
> IPL_DEV0 or IPL_DEV1, and the timer at IPL_TIMER.  Interrupts at and
> below that level are blocked, but arch_irqs_disabled() answered that
> interrupts were enabled.
>
> Treat any IPL above IPL_MIN, the level arch_local_irq_enable() restores,
> as interrupts disabled.  This matters as soon as lockdep is asked to
> track hardirq state, where irqs_disabled() is expected to be true inside
> an interrupt handler.
>

Hi Matt,

Thanks for the explanation, but I still do not think that treating every
raised IPL as "IRQs disabled" is correct.

The Alpha Architecture Reference Manual, Section 19.1.2, says that an
interrupt is delivered when its IPL is greater than the IPL in the
current PS. Table 19-1 in Section 19.2 documents the OSF PAL IPL range
from 0 to 7. An intermediate IPL therefore masks only interrupts at or
below that priority; higher-priority interrupts remain enabled. Only
IPL 7 masks all OS-visible interrupt levels.

The 21164 Hardware Reference Manual, Section 4.15.3, states the same
rule: an interrupt is enabled when the current IPL is less than the
interrupt's target IPL.

Thus, IPL_MIN means interrupts are enabled, an intermediate IPL is only
a partial mask, and IPL_MAX masks all interrupt levels.

I therefore think arch_irqs_disabled_flags() should retain the meaning
of fully disabled local IRQs:

        return (flags & 7) == IPL_MAX;

If lockdep or generic entry requires IRQs to be disabled on entry, I
think the entry code should first raise the live IPL to IPL_MAX, rather
than report an intermediate IPL as fully disabled.

Regards,
Magnus

[PATCH 02/24] alpha: enter hardirq context before looking up the irq descriptor

[Matt Turner]

handle_irq() called irq_to_desc() before irq_enter(), so that lookup ran
with the preempt count still saying task context and with RCU not yet
watching.  Generic code called from an interrupt handler should see
hardirq context, and irq_to_desc() is more than an array index once
SPARSE_IRQ is in use.

Move irq_enter() to the top of the function and add the matching
irq_exit() to the invalid interrupt path.

Assisted-by: Claude:claude-opus-5
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/kernel/irq.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git ./arch/alpha/kernel/irq.c ./arch/alpha/kernel/irq.c
index 4a6a8b1d5a8b..5867a1655045 100644
--- ./arch/alpha/kernel/irq.c
+++ ./arch/alpha/kernel/irq.c
@@ -107,18 +107,21 @@ handle_irq(int irq)
 	 * handled by some other CPU. (or is disabled)
 	 */
 	static unsigned int illegal_count=0;
-	struct irq_desc *desc = irq_to_desc(irq);
-	
+	struct irq_desc *desc;
+
+	irq_enter();
+
+	desc = irq_to_desc(irq);
 	if (!desc || ((unsigned) irq > ACTUAL_NR_IRQS &&
 	    illegal_count < MAX_ILLEGAL_IRQS)) {
 		irq_err_count++;
 		illegal_count++;
 		printk(KERN_CRIT "device_interrupt: invalid interrupt %d\n",
 		       irq);
+		irq_exit();
 		return;
 	}
 
-	irq_enter();
 	generic_handle_irq_desc(desc);
 	irq_exit();
 }
-- 
2.54.0

Re: [PATCH 02/24] alpha: enter hardirq context before looking up the irq descriptor

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:50 PM Matt Turner <mattst88@gmail.com> wrote:
>
> handle_irq() called irq_to_desc() before irq_enter(), so that lookup ran
> with the preempt count still saying task context and with RCU not yet
> watching.  Generic code called from an interrupt handler should see
> hardirq context, and irq_to_desc() is more than an array index once
> SPARSE_IRQ is in use.
>
> Move irq_enter() to the top of the function and add the matching
> irq_exit() to the invalid interrupt path.
>
> Assisted-by: Claude:claude-opus-5
> Signed-off-by: Matt Turner <mattst88@gmail.com>
> ---
>  arch/alpha/kernel/irq.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git ./arch/alpha/kernel/irq.c ./arch/alpha/kernel/irq.c
> index 4a6a8b1d5a8b..5867a1655045 100644
> --- ./arch/alpha/kernel/irq.c
> +++ ./arch/alpha/kernel/irq.c
> @@ -107,18 +107,21 @@ handle_irq(int irq)
>          * handled by some other CPU. (or is disabled)
>          */
>         static unsigned int illegal_count=0;
> -       struct irq_desc *desc = irq_to_desc(irq);
> -
> +       struct irq_desc *desc;
> +
> +       irq_enter();
> +
> +       desc = irq_to_desc(irq);
>         if (!desc || ((unsigned) irq > ACTUAL_NR_IRQS &&
>             illegal_count < MAX_ILLEGAL_IRQS)) {
>                 irq_err_count++;
>                 illegal_count++;
>                 printk(KERN_CRIT "device_interrupt: invalid interrupt %d\n",
>                        irq);
> +               irq_exit();
>                 return;
>         }
>
> -       irq_enter();
>         generic_handle_irq_desc(desc);
>         irq_exit();
>  }
> --
> 2.54.0
>

Going over this code again, I noticed what may be redundant hardirq
accounting in the existing device-interrupt path.

For type 3 interrupts, do_entInt() already wraps
alpha_mv.device_interrupt() in irq_enter()/irq_exit(). The platform
dispatcher then calls handle_irq(), which enters and exits hardirq
context again. Therefore, irq_to_desc() is already reached in hardirq
context before this patch. The patch moves it from nesting level one
to level two rather than from task context to hardirq context.

The RTC path does not have the outer irq_enter(), so the change is
needed there.

Would it be cleaner for do_entInt() to own the hardirq context for
both paths and remove the pair from handle_irq()? Or is there another
caller which requires handle_irq() to manage it itself?

I tested the patch on a two-CPU UP2000 with lockdep, IRQ flag tracing,
and sparse IRQs enabled. SCSI and network interrupts operated normally,
I observed no lockdep or IRQ-related warnings, and debug_locks remained
enabled in /proc/lockdep_stats.


Regards
Magnus

[PATCH 03/24] alpha: select ARCH_HAS_UBSAN

[Matt Turner]

GCC's undefined behavior sanitizer has no architecture-specific runtime
requirements. Enable it for Alpha to allow UBSAN instrumentation of the
kernel.

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
index e53ef2d88463..1aa76a2d9750 100644
--- ./arch/alpha/Kconfig
+++ ./arch/alpha/Kconfig
@@ -5,6 +5,7 @@ config ALPHA
 	select ARCH_32BIT_USTAT_F_TINODE
 	select ARCH_HAS_CURRENT_STACK_POINTER
 	select ARCH_HAS_DMA_OPS if PCI
+	select ARCH_HAS_UBSAN
 	select ARCH_MIGHT_HAVE_PC_PARPORT
 	select ARCH_MIGHT_HAVE_PC_SERIO
 	select ARCH_MODULE_NEEDS_WEAK_PER_CPU if SMP
-- 
2.54.0

Re: [PATCH 03/24] alpha: select ARCH_HAS_UBSAN

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:50 PM Matt Turner <mattst88@gmail.com> wrote:
>
> GCC's undefined behavior sanitizer has no architecture-specific runtime
> requirements. Enable it for Alpha to allow UBSAN instrumentation of the
> kernel.
>
I tested this patch on top of my rebased Alpha GENERIC_ENTRY patch on an
AlphaServer ES40. The kernel built and booted successfully with
CONFIG_UBSAN=y, and the UBSAN instrumentation is active.

CONFIG_UBSAN_ALIGNMENT did expose a misaligned struct bucket_table
allocation in lib/rhashtable.c. This appears to be a generic rhashtable
allocation-alignment issue rather than an Alpha UBSAN problem.

Tested-by: Magnus Lindholm <linmag7@gmail.com>
Reviewed-by: Magnus Lindholm <linmag7@gmail.com>

Regards,
Magnus

[PATCH 04/24] alpha: select ARCH_HAS_GCOV_PROFILE_ALL

[Matt Turner]

GCC's gcov instrumentation (-fprofile-arcs -ftest-coverage) has no
architecture-specific runtime requirements. Enable GCOV_PROFILE_ALL
support for Alpha to allow whole-kernel code coverage analysis.

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
index 1aa76a2d9750..a6024590ea6e 100644
--- ./arch/alpha/Kconfig
+++ ./arch/alpha/Kconfig
@@ -5,6 +5,7 @@ config ALPHA
 	select ARCH_32BIT_USTAT_F_TINODE
 	select ARCH_HAS_CURRENT_STACK_POINTER
 	select ARCH_HAS_DMA_OPS if PCI
+	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_HAS_UBSAN
 	select ARCH_MIGHT_HAVE_PC_PARPORT
 	select ARCH_MIGHT_HAVE_PC_SERIO
-- 
2.54.0

Re: [PATCH 04/24] alpha: select ARCH_HAS_GCOV_PROFILE_ALL

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:50 PM Matt Turner <mattst88@gmail.com> wrote:
>
> GCC's gcov instrumentation (-fprofile-arcs -ftest-coverage) has no
> architecture-specific runtime requirements. Enable GCOV_PROFILE_ALL
> support for Alpha to allow whole-kernel code coverage analysis.
>
> Assisted-by: Claude:claude-opus-4-6
> Signed-off-by: Matt Turner <mattst88@gmail.com>
> ---
>  arch/alpha/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
> index 1aa76a2d9750..a6024590ea6e 100644
> --- ./arch/alpha/Kconfig
> +++ ./arch/alpha/Kconfig
> @@ -5,6 +5,7 @@ config ALPHA
>         select ARCH_32BIT_USTAT_F_TINODE
>         select ARCH_HAS_CURRENT_STACK_POINTER
>         select ARCH_HAS_DMA_OPS if PCI
> +       select ARCH_HAS_GCOV_PROFILE_ALL
>         select ARCH_HAS_UBSAN
>         select ARCH_MIGHT_HAVE_PC_PARPORT
>         select ARCH_MIGHT_HAVE_PC_SERIO
> --
> 2.54.0
>
I built and booted this on a two-CPU UP2000 with GCOV_KERNEL and
GCOV_PROFILE_ALL enabled. Debugfs exposed 1226 .gcda files, including
the expected arch/alpha objects. I observed no GCOV-related errors or
kernel warnings.

This also appears to warrant changing Alpha from "TODO" to "ok" in
Documentation/features/debug/gcov-profile-all/arch-support.txt.

Tested-by: Magnus Lindholm <linmag7@gmail.com>
Reviewed-by: Magnus Lindholm <linmag7@gmail.com>

Regards,
Magnus

[PATCH 05/24] alpha: select HAVE_DEBUG_KMEMLEAK

[Matt Turner]

Kmemleak needs no architecture support beyond the standard linker script
symbols for the data and bss sections, which Alpha already provides, and
a scan of the kernel stacks, which is done generically.

Assisted-by: Claude:claude-opus-5
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
index a6024590ea6e..a435b71203f0 100644
--- ./arch/alpha/Kconfig
+++ ./arch/alpha/Kconfig
@@ -17,6 +17,7 @@ config ALPHA
 	select PCI_DOMAINS if PCI
 	select PCI_SYSCALL if PCI
 	select HAVE_ASM_MODVERSIONS
+	select HAVE_DEBUG_KMEMLEAK
 	select HAVE_PAGE_SIZE_8KB
 	select HAVE_PCSPKR_PLATFORM
 	select HAVE_PERF_EVENTS
-- 
2.54.0

Re: [PATCH 05/24] alpha: select HAVE_DEBUG_KMEMLEAK

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:50 PM Matt Turner <mattst88@gmail.com> wrote:
>
> Kmemleak needs no architecture support beyond the standard linker script
> symbols for the data and bss sections, which Alpha already provides, and
> a scan of the kernel stacks, which is done generically.
>

I tested this on an AlphaServer ES40 with CONFIG_DEBUG_KMEMLEAK=y.
The kernel built and booted successfully, and a manual kmemleak scan
completed normally.

The scan reported three suspected allocations from the sym53c8xx_2
driver. These appear unrelated to this patch and may be false
positives caused by references stored in DMA-coherent memory.
Either way, the patch looks good to me.

Tested-by: Magnus Lindholm <linmag7@gmail.com>
Reviewed-by: Magnus Lindholm <linmag7@gmail.com>

[PATCH 06/24] alpha: select EDAC_SUPPORT

[Matt Turner]

The EDAC core builds and works on Alpha; it only needs the architecture
to declare support.  There is no Alpha memory controller driver yet, but
the core is what a future driver, or the existing machine check error
decoding in err_ev6.c and err_ev7.c, would report through.

Assisted-by: Claude:claude-opus-5
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
index a435b71203f0..d2f9ef592f78 100644
--- ./arch/alpha/Kconfig
+++ ./arch/alpha/Kconfig
@@ -30,6 +30,7 @@ config ALPHA
 	select ARCH_WANT_IPC_PARSE_VERSION
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select AUDIT_ARCH
+	select EDAC_SUPPORT
 	select GENERIC_CPU_VULNERABILITIES
 	select GENERIC_SMP_IDLE_THREAD
 	select HAS_IOPORT
-- 
2.54.0

Re: [PATCH 06/24] alpha: select EDAC_SUPPORT

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:51 PM Matt Turner <mattst88@gmail.com> wrote:
>
> The EDAC core builds and works on Alpha; it only needs the architecture
> to declare support.  There is no Alpha memory controller driver yet, but
> the core is what a future driver, or the existing machine check error
> decoding in err_ev6.c and err_ev7.c, would report through.
>
I tested this on an AlphaServer ES40 with CONFIG_RAS=y and
CONFIG_EDAC=y. The kernel built and booted successfully, and the
generic EDAC sysfs hierarchy was created under
/sys/devices/system/edac/mc.

Possibly we could adapt this to have EDAC support, I know it was
mentioned on the list:

https://lore.kernel.org/linux-alpha/20251125224352.32034-1-linmag7@gmail.com/

Either way, this looks good to me,

Tested-by: Magnus Lindholm <linmag7@gmail.com>
Reviewed-by: Magnus Lindholm <linmag7@gmail.com>

[PATCH 07/24] alpha: select ARCH_SUPPORTS_ATOMIC_RMW

[Matt Turner]

Alpha has native LL/SC instructions (LDL_L/STL_C, LDQ_L/STQ_C) that
provide atomic read-modify-write capability, and already selects
ARCH_HAVE_NMI_SAFE_CMPXCHG.

Selecting ARCH_SUPPORTS_ATOMIC_RMW enables MUTEX_SPIN_ON_OWNER and
RWSEM_SPIN_ON_OWNER on SMP, allowing optimistic spinning on contended
locks rather than immediately sleeping.

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
index d2f9ef592f78..0655e36608cc 100644
--- ./arch/alpha/Kconfig
+++ ./arch/alpha/Kconfig
@@ -12,6 +12,7 @@ config ALPHA
 	select ARCH_MODULE_NEEDS_WEAK_PER_CPU if SMP
 	select ARCH_NO_PREEMPT
 	select ARCH_NO_SG_CHAIN
+	select ARCH_SUPPORTS_ATOMIC_RMW
 	select ARCH_USE_CMPXCHG_LOCKREF
 	select FORCE_PCI
 	select PCI_DOMAINS if PCI
-- 
2.54.0

Re: [PATCH 07/24] alpha: select ARCH_SUPPORTS_ATOMIC_RMW

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:51 PM Matt Turner <mattst88@gmail.com> wrote:
>
> Alpha has native LL/SC instructions (LDL_L/STL_C, LDQ_L/STQ_C) that
> provide atomic read-modify-write capability, and already selects
> ARCH_HAVE_NMI_SAFE_CMPXCHG.
>
> Selecting ARCH_SUPPORTS_ATOMIC_RMW enables MUTEX_SPIN_ON_OWNER and
> RWSEM_SPIN_ON_OWNER on SMP, allowing optimistic spinning on contended
> locks rather than immediately sleeping.
>

I tested this on an AlphaServer ES40 with four CPUs and
CONFIG_PROVE_LOCKING=y, CONFIG_DEBUG_MUTEXES=y, and
CONFIG_DEBUG_RWSEMS=y.

Both the mutex_lock and rwsem_lock locktorture tests completed
successfully under contention across all four CPUs.

Tested-by: Magnus Lindholm <linmag7@gmail.com>
Reviewed-by: Magnus Lindholm <linmag7@gmail.com>

Regards,
Magnus

[PATCH 08/24] alpha: select ARCH_HAS_FAST_MULTIPLIER

[Matt Turner]

All Alpha CPUs have hardware integer multiply (MULL/MULQ). EV4 and EV5
implement it in microcode; EV56 and later have fast single-cycle
multiply. Since no EV4 system is likely to run a modern kernel, select
this unconditionally to enable multiply-based fast paths in hweight and
string routines.

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
index 0655e36608cc..9e8e571949c4 100644
--- ./arch/alpha/Kconfig
+++ ./arch/alpha/Kconfig
@@ -5,6 +5,7 @@ config ALPHA
 	select ARCH_32BIT_USTAT_F_TINODE
 	select ARCH_HAS_CURRENT_STACK_POINTER
 	select ARCH_HAS_DMA_OPS if PCI
+	select ARCH_HAS_FAST_MULTIPLIER
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_HAS_UBSAN
 	select ARCH_MIGHT_HAVE_PC_PARPORT
-- 
2.54.0

Re: [PATCH 08/24] alpha: select ARCH_HAS_FAST_MULTIPLIER

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:51 PM Matt Turner <mattst88@gmail.com> wrote:
>
> All Alpha CPUs have hardware integer multiply (MULL/MULQ). EV4 and EV5
> implement it in microcode; EV56 and later have fast single-cycle
> multiply. Since no EV4 system is likely to run a modern kernel, select
> this unconditionally to enable multiply-based fast paths in hweight and
> string routines.
>

I tested this on an AlphaServer ES40 (EV67). A test module exercised
the multiplication-based memchr_inv() path with offsets 0 through 7,
buffer lengths from 17 through 257 bytes, four fill values, and
mismatches at the beginning, middle, and end of each buffer. All
tests passed.

On EV67, hweight uses the native CTPOP instruction, so the generic
multiplication-based hweight path is not selected by this configuration.

Tested-by: Magnus Lindholm <linmag7@gmail.com>
Reviewed-by: Magnus Lindholm <linmag7@gmail.com>

Regards,
Magnus

[PATCH 09/24] alpha: select ARCH_SUPPORTS_INT128

[Matt Turner]

gcc supports __int128 on Alpha, and the 64x64 to 128-bit multiply that
the users in the scheduler and in lib/ care about maps onto mulq/umulh
rather than an out-of-line libgcc helper.

Gate the select on CC_HAS_INT128 as the other 64-bit architectures do.

Assisted-by: Claude:claude-opus-5
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
index 9e8e571949c4..00365031ea6e 100644
--- ./arch/alpha/Kconfig
+++ ./arch/alpha/Kconfig
@@ -14,6 +14,7 @@ config ALPHA
 	select ARCH_NO_PREEMPT
 	select ARCH_NO_SG_CHAIN
 	select ARCH_SUPPORTS_ATOMIC_RMW
+	select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
 	select ARCH_USE_CMPXCHG_LOCKREF
 	select FORCE_PCI
 	select PCI_DOMAINS if PCI
-- 
2.54.0

Re: [PATCH 09/24] alpha: select ARCH_SUPPORTS_INT128

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:51 PM Matt Turner <mattst88@gmail.com> wrote:
>
> gcc supports __int128 on Alpha, and the 64x64 to 128-bit multiply that
> the users in the scheduler and in lib/ care about maps onto mulq/umulh
> rather than an out-of-line libgcc helper.
>
> Gate the select on CC_HAS_INT128 as the other 64-bit architectures do.
>

I tested this on an AlphaServer ES40 with
CONFIG_ARCH_SUPPORTS_INT128=y. The kernel built and booted
successfully, and the bits KUnit suite passed, including
genmask_u128_test:

  # bits-test: pass:6 fail:0 skip:0 total:6
  ok 1 bits-test

Tested-by: Magnus Lindholm <linmag7@gmail.com>
Reviewed-by: Magnus Lindholm <linmag7@gmail.com>

[PATCH 10/24] alpha: select HAVE_ARCH_COMPILER_H

[Matt Turner]

Alpha already provides asm/compiler.h (wrapping uapi/asm/compiler.h)
which defines architecture-specific compiler intrinsics like
__kernel_cmpbge, __kernel_cttz, __kernel_ctlz, and __kernel_ctpop.

Selecting HAVE_ARCH_COMPILER_H causes linux/compiler_types.h to include
asm/compiler.h, making these definitions available consistently.

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
index 00365031ea6e..6ccd03768083 100644
--- ./arch/alpha/Kconfig
+++ ./arch/alpha/Kconfig
@@ -19,6 +19,7 @@ config ALPHA
 	select FORCE_PCI
 	select PCI_DOMAINS if PCI
 	select PCI_SYSCALL if PCI
+	select HAVE_ARCH_COMPILER_H
 	select HAVE_ASM_MODVERSIONS
 	select HAVE_DEBUG_KMEMLEAK
 	select HAVE_PAGE_SIZE_8KB
-- 
2.54.0

Re: [PATCH 10/24] alpha: select HAVE_ARCH_COMPILER_H

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:51 PM Matt Turner <mattst88@gmail.com> wrote:
>
> Alpha already provides asm/compiler.h (wrapping uapi/asm/compiler.h)
> which defines architecture-specific compiler intrinsics like
> __kernel_cmpbge, __kernel_cttz, __kernel_ctlz, and __kernel_ctpop.
>
> Selecting HAVE_ARCH_COMPILER_H causes linux/compiler_types.h to include
> asm/compiler.h, making these definitions available consistently.


I tested this on an AlphaServer ES40. The kernel built and booted
successfully with CONFIG_HAVE_ARCH_COMPILER_H=y, and the in-tree
test_bitops module completed without errors.

While testing this patch, the FFS KUnit suite exposed a separate,
pre-existing issue in the EV67 Alpha fls64() implementation. The
zero-input tests failed with the contradictory diagnostic:

  Expected fls64(input) == 0, but
      fls64(input) == 0 (0x0)

The EV67 implementation passes zero to __kernel_ctlz(), which GCC maps
to __builtin_clzl(). The result of __builtin_clzl(0) is undefined, so
the compiler can optimize the comparison inconsistently with the value
returned by the Alpha ctlz instruction.

I verified the diagnosis by changing fls64() to handle zero explicitly:

  return word ? 64 - __kernel_ctlz(word) : 0;

With that change, the FFS KUnit result improved from 8/9 to 9/9 tests
passing.

This appears unrelated to this patch, since asm/bitops.h already
included asm/compiler.h directly before HAVE_ARCH_COMPILER_H was
selected. I am mentioning it here since this patch led to the issue
being discovered.

Tested-by: Magnus Lindholm <linmag7@gmail.com>
Reviewed-by: Magnus Lindholm <linmag7@gmail.com>

[PATCH 11/24] alpha: select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE

[Matt Turner]

Alpha has a clean split between user and kernel address spaces: user
space occupies 0x0000000000000000-0x000003ffffffffff (TASK_SIZE), while
kernel space uses KSEG and vmalloc regions near the top of the 64-bit
address space. These are strictly non-overlapping.

This enables optimizations in BPF and tracing that can skip address
range checks when user and kernel pointers are distinguishable by
address alone.

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
index 6ccd03768083..2ae514bea4cf 100644
--- ./arch/alpha/Kconfig
+++ ./arch/alpha/Kconfig
@@ -7,6 +7,7 @@ config ALPHA
 	select ARCH_HAS_DMA_OPS if PCI
 	select ARCH_HAS_FAST_MULTIPLIER
 	select ARCH_HAS_GCOV_PROFILE_ALL
+	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
 	select ARCH_HAS_UBSAN
 	select ARCH_MIGHT_HAVE_PC_PARPORT
 	select ARCH_MIGHT_HAVE_PC_SERIO
-- 
2.54.0

Re: [PATCH 11/24] alpha: select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:51 PM Matt Turner <mattst88@gmail.com> wrote:
>
> Alpha has a clean split between user and kernel address spaces: user
> space occupies 0x0000000000000000-0x000003ffffffffff (TASK_SIZE), while
> kernel space uses KSEG and vmalloc regions near the top of the 64-bit
> address space. These are strictly non-overlapping.
>
> This enables optimizations in BPF and tracing that can skip address
> range checks when user and kernel pointers are distinguishable by
> address alone.
>

I tested this on an AlphaServer ES40. The kernel built and booted
successfully with CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE=y.

I verified that userspace mappings were below TASK_SIZE
(0x0000040000000000), while the kernel text was in the high Alpha
kernel address range:

  0x000002000025a000  highest observed userspace mapping
  0xfffffc0000310000  _stext

This confirms that the observed user and kernel virtual address ranges
are non-overlapping.

Tested-by: Magnus Lindholm <linmag7@gmail.com>
Reviewed-by: Magnus Lindholm <linmag7@gmail.com>

[PATCH 12/24] alpha: add HAVE_ARCH_THREAD_STRUCT_WHITELIST support

[Matt Turner]

Alpha's thread_struct is empty (all per-thread state lives in
thread_info), so the whitelist is trivially empty. This is more
explicit than the generic fallback, which computes the full
thread_struct size as copyable.

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/Kconfig                 | 1 +
 arch/alpha/include/asm/processor.h | 7 +++++++
 2 files changed, 8 insertions(+)

diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
index 2ae514bea4cf..e6fa8da0abff 100644
--- ./arch/alpha/Kconfig
+++ ./arch/alpha/Kconfig
@@ -42,6 +42,7 @@ config ALPHA
 	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_ARCH_SECCOMP
 	select HAVE_ARCH_SECCOMP_FILTER
+	select HAVE_ARCH_THREAD_STRUCT_WHITELIST
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_MOD_ARCH_SPECIFIC
 	select LOCK_MM_AND_FIND_VMA
diff --git ./arch/alpha/include/asm/processor.h ./arch/alpha/include/asm/processor.h
index 5dce5518a211..c461a26d47b3 100644
--- ./arch/alpha/include/asm/processor.h
+++ ./arch/alpha/include/asm/processor.h
@@ -26,6 +26,13 @@
 struct thread_struct { };
 #define INIT_THREAD  { }
 
+static inline void arch_thread_struct_whitelist(unsigned long *offset,
+						unsigned long *size)
+{
+	*offset = 0;
+	*size = 0;
+}
+
 /* Do necessary setup to start up a newly executed thread.  */
 struct pt_regs;
 extern void start_thread(struct pt_regs *, unsigned long, unsigned long);
-- 
2.54.0

Re: [PATCH 12/24] alpha: add HAVE_ARCH_THREAD_STRUCT_WHITELIST support

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:51 PM Matt Turner <mattst88@gmail.com> wrote:
>
> Alpha's thread_struct is empty (all per-thread state lives in
> thread_info), so the whitelist is trivially empty. This is more
> explicit than the generic fallback, which computes the full
> thread_struct size as copyable.
>
> Assisted-by: Claude:claude-opus-4-6
> Signed-off-by: Matt Turner <mattst88@gmail.com>


I tested this on an AlphaServer ES40 with
CONFIG_HARDENED_USERCOPY=y.

The task_struct slab reports a zero-sized usercopy region, as expected
for Alpha's empty thread_struct:

  $ cat /sys/kernel/slab/task_struct/usersize
  0

The usercopy KUnit suite also passed all tests:

  # usercopy: pass:4 fail:0 skip:0 total:4
  ok 1 usercopy

Tested-by: Magnus Lindholm <linmag7@gmail.com>
Reviewed-by: Magnus Lindholm <linmag7@gmail.com>

[PATCH 13/24] alpha: add ARCH_HAS_PTE_SPECIAL support

[Matt Turner]

Add _PAGE_SPECIAL using bit 19 (0x80000), which is unused in the Alpha
PTE layout. This enables pte_special()/pte_mkspecial() for marking PTEs
that are not backed by struct page (VDSO mappings, zero page,
io_remap_pfn_range, etc.).

Include _PAGE_SPECIAL in _PAGE_CHG_MASK so it is preserved across
pte_modify() calls.

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/Kconfig               | 1 +
 arch/alpha/include/asm/pgtable.h | 5 ++++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
index e6fa8da0abff..4c38405cd6cd 100644
--- ./arch/alpha/Kconfig
+++ ./arch/alpha/Kconfig
@@ -8,6 +8,7 @@ config ALPHA
 	select ARCH_HAS_FAST_MULTIPLIER
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
+	select ARCH_HAS_PTE_SPECIAL
 	select ARCH_HAS_UBSAN
 	select ARCH_MIGHT_HAVE_PC_PARPORT
 	select ARCH_MIGHT_HAVE_PC_SERIO
diff --git ./arch/alpha/include/asm/pgtable.h ./arch/alpha/include/asm/pgtable.h
index 8e00cf9dc39d..bdff33b505bc 100644
--- ./arch/alpha/include/asm/pgtable.h
+++ ./arch/alpha/include/asm/pgtable.h
@@ -73,6 +73,7 @@ struct vm_area_struct;
 /* .. and these are ours ... */
 #define _PAGE_DIRTY	0x20000
 #define _PAGE_ACCESSED	0x40000
+#define _PAGE_SPECIAL	0x80000
 
 /* We borrow bit 39 to store the exclusive marker in swap PTEs. */
 #define _PAGE_SWP_EXCLUSIVE	0x8000000000UL
@@ -94,7 +95,7 @@ struct vm_area_struct;
 #define _PFN_MASK	0xFFFFFFFF00000000UL
 
 #define _PAGE_TABLE	(_PAGE_VALID | __DIRTY_BITS | __ACCESS_BITS)
-#define _PAGE_CHG_MASK	(_PFN_MASK | __DIRTY_BITS | __ACCESS_BITS)
+#define _PAGE_CHG_MASK	(_PFN_MASK | __DIRTY_BITS | __ACCESS_BITS | _PAGE_SPECIAL)
 
 /*
  * All the normal masks have the "page accessed" bits on, as any time they are used,
@@ -238,6 +239,8 @@ extern inline pte_t pte_mkold(pte_t pte)	{ pte_val(pte) &= ~(__ACCESS_BITS); ret
 extern inline pte_t pte_mkwrite_novma(pte_t pte){ pte_val(pte) &= ~_PAGE_FOW; return pte; }
 extern inline pte_t pte_mkdirty(pte_t pte)	{ pte_val(pte) |= __DIRTY_BITS; return pte; }
 extern inline pte_t pte_mkyoung(pte_t pte)	{ pte_val(pte) |= __ACCESS_BITS; return pte; }
+extern inline int pte_special(pte_t pte)	{ return pte_val(pte) & _PAGE_SPECIAL; }
+extern inline pte_t pte_mkspecial(pte_t pte)	{ pte_val(pte) |= _PAGE_SPECIAL; return pte; }
 
 /*
  * The smp_rmb() in the following functions are required to order the load of
-- 
2.54.0

Re: [PATCH 13/24] alpha: add ARCH_HAS_PTE_SPECIAL support

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:51 PM Matt Turner <mattst88@gmail.com> wrote:
>
> Add _PAGE_SPECIAL using bit 19 (0x80000), which is unused in the Alpha
> PTE layout. This enables pte_special()/pte_mkspecial() for marking PTEs
> that are not backed by struct page (VDSO mappings, zero page,
> io_remap_pfn_range, etc.).
>
> Include _PAGE_SPECIAL in _PAGE_CHG_MASK so it is preserved across
> pte_modify() calls.
>
> Assisted-by: Claude:claude-opus-4-6
> Signed-off-by: Matt Turner <mattst88@gmail.com>

I tested this on an AlphaServer ES40 with
CONFIG_ARCH_HAS_PTE_SPECIAL=y.

A focused anonymous-memory test faulted in 256 shared zero pages,
changed their protections from read-write to read-only and back, and
then wrote to every page to trigger replacement with private COW pages.

The test completed successfully, all data checks passed, and no
page-table or bad-PTE warnings appeared in dmesg.

Tested-by: Magnus Lindholm <linmag7@gmail.com>
Reviewed-by: Magnus Lindholm <linmag7@gmail.com>

[PATCH 14/24] alpha: add ARCH_SUPPORTS_PAGE_TABLE_CHECK support

[Matt Turner]

Add the page table check helpers needed for CONFIG_PAGE_TABLE_CHECK
and select ARCH_SUPPORTS_PAGE_TABLE_CHECK in Kconfig.

Alpha does not support huge pages, so pmd_user_accessible_page() and
pud_user_accessible_page() always return false. pte_user_accessible_page()
checks for present PTEs with user read access (_PAGE_URE).

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/Kconfig               |  1 +
 arch/alpha/include/asm/pgtable.h | 16 ++++++++++++++++
 2 files changed, 17 insertions(+)

diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
index 4c38405cd6cd..d7e2859aaedb 100644
--- ./arch/alpha/Kconfig
+++ ./arch/alpha/Kconfig
@@ -17,6 +17,7 @@ config ALPHA
 	select ARCH_NO_SG_CHAIN
 	select ARCH_SUPPORTS_ATOMIC_RMW
 	select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
+	select ARCH_SUPPORTS_PAGE_TABLE_CHECK
 	select ARCH_USE_CMPXCHG_LOCKREF
 	select FORCE_PCI
 	select PCI_DOMAINS if PCI
diff --git ./arch/alpha/include/asm/pgtable.h ./arch/alpha/include/asm/pgtable.h
index bdff33b505bc..310361920a1f 100644
--- ./arch/alpha/include/asm/pgtable.h
+++ ./arch/alpha/include/asm/pgtable.h
@@ -232,6 +232,22 @@ extern inline void pud_clear(pud_t * pudp)	{ pud_val(*pudp) = 0; }
 extern inline int pte_write(pte_t pte)		{ return !(pte_val(pte) & _PAGE_FOW); }
 extern inline int pte_dirty(pte_t pte)		{ return pte_val(pte) & _PAGE_DIRTY; }
 extern inline int pte_young(pte_t pte)		{ return pte_val(pte) & _PAGE_ACCESSED; }
+extern inline int pte_user(pte_t pte)		{ return pte_val(pte) & _PAGE_URE; }
+
+static inline bool pte_user_accessible_page(pte_t pte, unsigned long addr)
+{
+	return pte_present(pte) && pte_user(pte);
+}
+
+static inline bool pmd_user_accessible_page(pmd_t pmd, unsigned long addr)
+{
+	return false;
+}
+
+static inline bool pud_user_accessible_page(pud_t pud, unsigned long addr)
+{
+	return false;
+}
 
 extern inline pte_t pte_wrprotect(pte_t pte)	{ pte_val(pte) |= _PAGE_FOW; return pte; }
 extern inline pte_t pte_mkclean(pte_t pte)	{ pte_val(pte) &= ~(__DIRTY_BITS); return pte; }
-- 
2.54.0

Re: [PATCH 14/24] alpha: add ARCH_SUPPORTS_PAGE_TABLE_CHECK support

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:51 PM Matt Turner <mattst88@gmail.com> wrote:
>
> Add the page table check helpers needed for CONFIG_PAGE_TABLE_CHECK
> and select ARCH_SUPPORTS_PAGE_TABLE_CHECK in Kconfig.
>
> Alpha does not support huge pages, so pmd_user_accessible_page() and
> pud_user_accessible_page() always return false. pte_user_accessible_page()
> checks for present PTEs with user read access (_PAGE_URE).
>

This patch does not build with CONFIG_PAGE_TABLE_CHECK enabled on
v7.3-rc1.

Commit cf8771ca4cdb ("mm/page_table_check: Pass mm_struct to
pxx_user_accessible_page()") changed these helpers from:

        pte_user_accessible_page(pte, addr)

to:

        pte_user_accessible_page(mm, addr, pte)

The Alpha definitions added here still use the old two-argument API.
The same applies to pmd_user_accessible_page() and
pud_user_accessible_page().

Could you update the helpers to use the new three-argument signatures?

Regards,
Magnus

[PATCH 15/24] alpha: select ARCH_HAS_DEBUG_VM_PGTABLE

[Matt Turner]

CONFIG_DEBUG_VM_PGTABLE runs a boot-time self test over the page table
helpers: the protection bit accessors, pte_modify(), the swap entry
encoding including the exclusive marker, and, where the architecture
supports them, the huge page helpers.  Alpha implements everything the
test needs for a three-level page table without huge page support.

Assisted-by: Claude:claude-opus-5
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
index d7e2859aaedb..87fe81bc4709 100644
--- ./arch/alpha/Kconfig
+++ ./arch/alpha/Kconfig
@@ -4,6 +4,7 @@ config ALPHA
 	default y
 	select ARCH_32BIT_USTAT_F_TINODE
 	select ARCH_HAS_CURRENT_STACK_POINTER
+	select ARCH_HAS_DEBUG_VM_PGTABLE
 	select ARCH_HAS_DMA_OPS if PCI
 	select ARCH_HAS_FAST_MULTIPLIER
 	select ARCH_HAS_GCOV_PROFILE_ALL
-- 
2.54.0

Re: [PATCH 15/24] alpha: select ARCH_HAS_DEBUG_VM_PGTABLE

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:51 PM Matt Turner <mattst88@gmail.com> wrote:
>
> CONFIG_DEBUG_VM_PGTABLE runs a boot-time self test over the page table
> helpers: the protection bit accessors, pte_modify(), the swap entry
> encoding including the exclusive marker, and, where the architecture
> supports them, the huge page helpers.  Alpha implements everything the
> test needs for a three-level page table without huge page support.
>
> Assisted-by: Claude:claude-opus-5
> Signed-off-by: Matt Turner <mattst88@gmail.com>
> ---
>  arch/alpha/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
> index d7e2859aaedb..87fe81bc4709 100644
> --- ./arch/alpha/Kconfig
> +++ ./arch/alpha/Kconfig
> @@ -4,6 +4,7 @@ config ALPHA
>         default y
>         select ARCH_32BIT_USTAT_F_TINODE
>         select ARCH_HAS_CURRENT_STACK_POINTER
> +       select ARCH_HAS_DEBUG_VM_PGTABLE
>         select ARCH_HAS_DMA_OPS if PCI
>         select ARCH_HAS_FAST_MULTIPLIER
>         select ARCH_HAS_GCOV_PROFILE_ALL
> --
> 2.54.0
>

I applied this manually on top of v7.3-rc1 plus Alpha GENERIC_ENTRY v5.
The Kconfig hunk needed a trivial context adjustment.

I built and booted it on a two-CPU UP2000 with
ARCH_HAS_DEBUG_VM_PGTABLE and DEBUG_VM_PGTABLE enabled. The boot-time
page-table helper validation ran without warnings.

This also appears to warrant changing Alpha from "TODO" to "ok" in
Documentation/features/debug/debug-vm-pgtable/arch-support.txt.

Tested-by: Magnus Lindholm <linmag7@gmail.com>
Reviewed-by: Magnus Lindholm <linmag7@gmail.com>

Regards,
Magnus

[PATCH 16/24] alpha: select HAVE_GUP_FAST

[Matt Turner]

The lockless GUP fast path needs the architecture to distinguish PTEs
with no struct page behind them and to keep page table pages alive while
a walker holds no lock.  Alpha now has ARCH_HAS_PTE_SPECIAL, and it has
selected MMU_GATHER_RCU_TABLE_FREE for a long time, so both requirements
are met.

PTEs are a single 64-bit word on Alpha, so the lockless reads that the
generic walker performs cannot tear, and no arch-specific
gup_fast_permitted() or ptep_get_lockless() is needed.

Assisted-by: Claude:claude-opus-5
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
index 87fe81bc4709..352615956b1e 100644
--- ./arch/alpha/Kconfig
+++ ./arch/alpha/Kconfig
@@ -26,6 +26,7 @@ config ALPHA
 	select HAVE_ARCH_COMPILER_H
 	select HAVE_ASM_MODVERSIONS
 	select HAVE_DEBUG_KMEMLEAK
+	select HAVE_GUP_FAST
 	select HAVE_PAGE_SIZE_8KB
 	select HAVE_PCSPKR_PLATFORM
 	select HAVE_PERF_EVENTS
-- 
2.54.0

Re: [PATCH 16/24] alpha: select HAVE_GUP_FAST

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:51 PM Matt Turner <mattst88@gmail.com> wrote:
>
> The lockless GUP fast path needs the architecture to distinguish PTEs
> with no struct page behind them and to keep page table pages alive while
> a walker holds no lock.  Alpha now has ARCH_HAS_PTE_SPECIAL, and it has
> selected MMU_GATHER_RCU_TABLE_FREE for a long time, so both requirements
> are met.
>
> PTEs are a single 64-bit word on Alpha, so the lockless reads that the
> generic walker performs cannot tear, and no arch-specific
> gup_fast_permitted() or ptep_get_lockless() is needed.
>
> Assisted-by: Claude:claude-opus-5
> Signed-off-by: Matt Turner <mattst88@gmail.com>


I tested this on an Alpha UP2000 with CONFIG_HAVE_GUP_FAST=y,
CONFIG_ARCH_HAS_PTE_SPECIAL=y, and
CONFIG_MMU_GATHER_RCU_TABLE_FREE=y.

The in-tree gup_test completed the get_user_pages_fast() and
pin_user_pages_fast() benchmarks with both read-only and writable pins.
Each case ran ten iterations over a 16 MiB mapping, fetching 123 pages
per call.

All four cases completed with ioctl status 0 and no failures.

Tested-by: Magnus Lindholm <linmag7@gmail.com>
Reviewed-by: Magnus Lindholm <linmag7@gmail.com>

[PATCH 17/24] alpha: select ARCH_USE_MEMTEST

[Matt Turner]

Wire up the generic early memtest from arch_mm_preinit(), which runs
after parse_early_param() has picked up the memtest= command line option
and before memblock_free_all() hands the memory to the buddy allocator.
paging_init() would be the natural place, but Alpha calls it from
setup_arch(), before the option is parsed, so the test would never run.

The test range starts at the first DRAM address rather than physical zero
because low memory on Alpha is owned by the console and PALcode.

Tested under QEMU with memtest=4: all four patterns pass over the free
memblock ranges, with no bad memory reserved.

Assisted-by: Claude:claude-opus-5
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/Kconfig   | 1 +
 arch/alpha/mm/init.c | 5 +++++
 2 files changed, 6 insertions(+)

diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
index 352615956b1e..c4b4a9b8d770 100644
--- ./arch/alpha/Kconfig
+++ ./arch/alpha/Kconfig
@@ -20,6 +20,7 @@ config ALPHA
 	select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
 	select ARCH_SUPPORTS_PAGE_TABLE_CHECK
 	select ARCH_USE_CMPXCHG_LOCKREF
+	select ARCH_USE_MEMTEST
 	select FORCE_PCI
 	select PCI_DOMAINS if PCI
 	select PCI_SYSCALL if PCI
diff --git ./arch/alpha/mm/init.c ./arch/alpha/mm/init.c
index f4d65a60c869..6c28947d6e2d 100644
--- ./arch/alpha/mm/init.c
+++ ./arch/alpha/mm/init.c
@@ -226,6 +226,11 @@ void __init paging_init(void)
 	memset(absolute_pointer(ZERO_PGE), 0, PAGE_SIZE);
 }
 
+void __init arch_mm_preinit(void)
+{
+	early_memtest(memblock_start_of_DRAM(), PFN_PHYS(max_low_pfn));
+}
+
 #if defined(CONFIG_ALPHA_GENERIC) || defined(CONFIG_ALPHA_SRM)
 void
 srm_paging_stop (void)
-- 
2.54.0

Re: [PATCH 17/24] alpha: select ARCH_USE_MEMTEST

[Magnus Lindholm]

On Tue, Sep 1, 2026 at 5:51 PM Matt Turner <mattst88@gmail.com> wrote:
>
> Wire up the generic early memtest from arch_mm_preinit(), which runs
> after parse_early_param() has picked up the memtest= command line option
> and before memblock_free_all() hands the memory to the buddy allocator.
> paging_init() would be the natural place, but Alpha calls it from
> setup_arch(), before the option is parsed, so the test would never run.
>
> The test range starts at the first DRAM address rather than physical zero
> because low memory on Alpha is owned by the console and PALcode.
>
> Tested under QEMU with memtest=4: all four patterns pass over the free
> memblock ranges, with no bad memory reserved.
>
> Assisted-by: Claude:claude-opus-5
> Signed-off-by: Matt Turner <mattst88@gmail.com>


I tested this on an Alpha UP2000 with CONFIG_MEMTEST=y and memtest=4.
The early memory test completed successfully and reported:

  EarlyMemtestBad:       0 kB

It would also be useful to add ALPHA to the memtest= architecture list
in Documentation/admin-guide/kernel-parameters.txt.

Tested-by: Magnus Lindholm <linmag7@gmail.com>
Reviewed-by: Magnus Lindholm <linmag7@gmail.com>

[PATCH 18/24] alpha: select SYSCTL_EXCEPTION_TRACE

[Matt Turner]

Report unhandled user faults the way other architectures do, and hook up
the debug.exception-trace sysctl that controls the reporting.

The message gives the faulting address, the PC and the user stack
pointer, and is rate limited.

Assisted-by: Claude:claude-opus-5
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/Kconfig    |  1 +
 arch/alpha/mm/fault.c | 29 +++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
index c4b4a9b8d770..4c60c442207c 100644
--- ./arch/alpha/Kconfig
+++ ./arch/alpha/Kconfig
@@ -59,6 +59,7 @@ config ALPHA
 	select MMU_GATHER_NO_RANGE
 	select MMU_GATHER_RCU_TABLE_FREE
 	select SPARSEMEM_EXTREME if SPARSEMEM
+	select SYSCTL_EXCEPTION_TRACE
 	select ZONE_DMA
 	select TRACE_IRQFLAGS_SUPPORT
 	select ARCH_WANT_FRAME_POINTERS
diff --git ./arch/alpha/mm/fault.c ./arch/alpha/mm/fault.c
index a9816bbc9f34..dfe427d93072 100644
--- ./arch/alpha/mm/fault.c
+++ ./arch/alpha/mm/fault.c
@@ -27,8 +27,32 @@
 #include <linux/uaccess.h>
 #include <linux/perf_event.h>
 
+#include <asm/pal.h>
+
 extern void die_if_kernel(char *,struct pt_regs *,long, unsigned long *);
 
+int show_unhandled_signals = 1;
+
+static void
+show_signal_msg(struct pt_regs *regs, unsigned long address, int signo,
+		const char *desc)
+{
+	const char *level;
+
+	if (!show_unhandled_signals || !unhandled_signal(current, signo))
+		return;
+	if (!printk_ratelimit())
+		return;
+
+	/* Losing init is fatal, so shout about it.  */
+	level = task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG;
+
+	printk("%s%s[%d]: %s at %016lx pc %016lx sp %016lx\n",
+	       level, current->comm, task_pid_nr(current), desc,
+	       address, regs->pc, rdusp());
+	print_vma_addr(KERN_CONT "  in ", regs->pc);
+	printk(KERN_CONT "\n");
+}
 
 /*
  * Force a new ASN for a task.
@@ -217,12 +241,17 @@ do_page_fault(unsigned long address, unsigned long mmcsr,
 	mmap_read_unlock(mm);
 	/* Send a sigbus, regardless of whether we were in kernel
 	   or user mode.  */
+	if (user_mode(regs))
+		show_signal_msg(regs, address, SIGBUS, "bus error");
 	force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *) address);
 	if (!user_mode(regs))
 		goto no_context;
 	return;
 
  do_sigsegv:
+	show_signal_msg(regs, address, SIGSEGV,
+			si_code == SEGV_MAPERR ? "unmapped access"
+					       : "access violation");
 	force_sig_fault(SIGSEGV, si_code, (void __user *) address);
 	return;
 
-- 
2.54.0

Re: [PATCH 18/24] alpha: select SYSCTL_EXCEPTION_TRACE

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:51 PM Matt Turner <mattst88@gmail.com> wrote:
>
> Report unhandled user faults the way other architectures do, and hook up
> the debug.exception-trace sysctl that controls the reporting.
>
> The message gives the faulting address, the PC and the user stack
> pointer, and is rate limited.
>
> Assisted-by: Claude:claude-opus-5
> Signed-off-by: Matt Turner <mattst88@gmail.com>
> ---

I tested this on an Alpha UP2000. With debug.exception-trace=1,
unhandled SEGV_MAPERR and SEGV_ACCERR faults produced the expected
"unmapped access" and "access violation" messages.

With debug.exception-trace=0, both processes still received SIGSEGV,
but no additional messages were written to the kernel log.

Tested-by: Magnus Lindholm <linmag7@gmail.com>
Reviewed-by: Magnus Lindholm <linmag7@gmail.com>

[PATCH 19/24] alpha: discard .eh_frame and the relocation sections

[Matt Turner]

gcc emits .eh_frame for Alpha even though the kernel builds with
-fno-asynchronous-unwind-tables, and nothing in the kernel consumes it:
the stack trace code scans the stack for text addresses rather than
unwinding DWARF.  It was allocated in the loaded image, so dropping it
shrinks vmlinux by about 1.1MB for a Marvel SMP configuration.

The .rela* sections are equally useless, as the kernel image is not
relocatable.  The linker was already dropping their contents.

Both were being placed as orphan sections, which is what drew attention
to them.

Assisted-by: Claude:claude-opus-5
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/kernel/vmlinux.lds.S | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git ./arch/alpha/kernel/vmlinux.lds.S ./arch/alpha/kernel/vmlinux.lds.S
index 95704e64b6a6..c44941d3b874 100644
--- ./arch/alpha/kernel/vmlinux.lds.S
+++ ./arch/alpha/kernel/vmlinux.lds.S
@@ -76,5 +76,16 @@ SECTIONS
 	MODINFO
 	ELF_DETAILS
 
+	/*
+	 * gcc emits .eh_frame for Alpha even with
+	 * -fno-asynchronous-unwind-tables, and the kernel has no DWARF
+	 * unwinder to consume it.  The relocation sections are likewise
+	 * useless as the kernel image is not relocatable.
+	 */
+	/DISCARD/ : {
+		*(.eh_frame)
+		*(.rela .rela*)
+	}
+
 	DISCARDS
 }
-- 
2.54.0

Re: [PATCH 19/24] alpha: discard .eh_frame and the relocation sections

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:51 PM Matt Turner <mattst88@gmail.com> wrote:
>
> gcc emits .eh_frame for Alpha even though the kernel builds with
> -fno-asynchronous-unwind-tables, and nothing in the kernel consumes it:
> the stack trace code scans the stack for text addresses rather than
> unwinding DWARF.  It was allocated in the loaded image, so dropping it
> shrinks vmlinux by about 1.1MB for a Marvel SMP configuration.
>
> The .rela* sections are equally useless, as the kernel image is not
> relocatable.  The linker was already dropping their contents.
>
> Both were being placed as orphan sections, which is what drew attention
> to them.
>
> Assisted-by: Claude:claude-opus-5
> Signed-off-by: Matt Turner <mattst88@gmail.com>
> ---

I verified that .eh_frame and .rela* sections were present in the
linker input objects but absent from the final vmlinux. The resulting
compressed kernel image also booted successfully on an Alpha UP2000.

Tested-by: Magnus Lindholm <linmag7@gmail.com>
Reviewed-by: Magnus Lindholm <linmag7@gmail.com>

[PATCH 20/24] alpha: select ARCH_WANT_LD_ORPHAN_WARN

[Matt Turner]

With .eh_frame and the relocation sections now placed explicitly, an
Alpha kernel links with no orphan sections left, so ask the linker to
warn if new ones appear.

Assisted-by: Claude:claude-opus-5
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
index 4c60c442207c..827b224f2f8a 100644
--- ./arch/alpha/Kconfig
+++ ./arch/alpha/Kconfig
@@ -38,6 +38,7 @@ config ALPHA
 	select AUTO_IRQ_AFFINITY if SMP
 	select GENERIC_IRQ_SHOW
 	select ARCH_WANT_IPC_PARSE_VERSION
+	select ARCH_WANT_LD_ORPHAN_WARN
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select AUDIT_ARCH
 	select EDAC_SUPPORT
-- 
2.54.0

Re: [PATCH 20/24] alpha: select ARCH_WANT_LD_ORPHAN_WARN

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:51 PM Matt Turner <mattst88@gmail.com> wrote:
>
> With .eh_frame and the relocation sections now placed explicitly, an
> Alpha kernel links with no orphan sections left, so ask the linker to
> warn if new ones appear.
>
> Assisted-by: Claude:claude-opus-5
> Signed-off-by: Matt Turner <mattst88@gmail.com>

Build tested this for Alpla, looks good to me.

Tested-by: Magnus Lindholm <linmag7@gmail.com>
Reviewed-by: Magnus Lindholm <linmag7@gmail.com>

> ---
>  arch/alpha/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
> index 4c60c442207c..827b224f2f8a 100644
> --- ./arch/alpha/Kconfig
> +++ ./arch/alpha/Kconfig
> @@ -38,6 +38,7 @@ config ALPHA
>         select AUTO_IRQ_AFFINITY if SMP
>         select GENERIC_IRQ_SHOW
>         select ARCH_WANT_IPC_PARSE_VERSION
> +       select ARCH_WANT_LD_ORPHAN_WARN
>         select ARCH_HAVE_NMI_SAFE_CMPXCHG
>         select AUDIT_ARCH
>         select EDAC_SUPPORT
> --
> 2.54.0
>

[PATCH 21/24] alpha: select ARCH_WANT_IRQS_OFF_ACTIVATE_MM

[Matt Turner]

activate_mm() on Alpha calls __load_new_mm_context() which assigns a
new ASID and invokes PALcode swpctx. On SMP, an interrupt arriving
between the ASID update and the page table switch could see
inconsistent state. Ensure activate_mm() is called with interrupts
disabled during exec.

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
index 827b224f2f8a..bda8443a7323 100644
--- ./arch/alpha/Kconfig
+++ ./arch/alpha/Kconfig
@@ -37,6 +37,7 @@ config ALPHA
 	select GENERIC_PCI_IOMAP
 	select AUTO_IRQ_AFFINITY if SMP
 	select GENERIC_IRQ_SHOW
+	select ARCH_WANT_IRQS_OFF_ACTIVATE_MM
 	select ARCH_WANT_IPC_PARSE_VERSION
 	select ARCH_WANT_LD_ORPHAN_WARN
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
-- 
2.54.0

Re: [PATCH 21/24] alpha: select ARCH_WANT_IRQS_OFF_ACTIVATE_MM

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:51 PM Matt Turner <mattst88@gmail.com> wrote:
>
> activate_mm() on Alpha calls __load_new_mm_context() which assigns a
> new ASID and invokes PALcode swpctx. On SMP, an interrupt arriving
> between the ASID update and the page table switch could see
> inconsistent state. Ensure activate_mm() is called with interrupts
> disabled during exec.
>
> Assisted-by: Claude:claude-opus-4-6
> Signed-off-by: Matt Turner <mattst88@gmail.com>
> ---
>  arch/alpha/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
> index 827b224f2f8a..bda8443a7323 100644
> --- ./arch/alpha/Kconfig
> +++ ./arch/alpha/Kconfig
> @@ -37,6 +37,7 @@ config ALPHA
>         select GENERIC_PCI_IOMAP
>         select AUTO_IRQ_AFFINITY if SMP
>         select GENERIC_IRQ_SHOW
> +       select ARCH_WANT_IRQS_OFF_ACTIVATE_MM
>         select ARCH_WANT_IPC_PARSE_VERSION
>         select ARCH_WANT_LD_ORPHAN_WARN
>         select ARCH_HAVE_NMI_SAFE_CMPXCHG
> --
> 2.54.0
>

I tested this on a two-CPU Alpha UP2000. I ran 20,000 successive
execve() operations pinned to each online CPU. All executions completed
successfully, with no MMU, ASN, or page-table errors in the kernel log.

Tested-by: Magnus Lindholm <linmag7@gmail.com>
Reviewed-by: Magnus Lindholm <linmag7@gmail.com>

Magnus

[PATCH 22/24] alpha: add HAVE_PERF_REGS and HAVE_PERF_USER_STACK_DUMP support

[Matt Turner]

Implement the perf register sampling interface for Alpha. This enables
perf to capture register state and user stack dumps with samples,
supporting --call-graph dwarf.

The perf_regs enum exposes the registers available in pt_regs: r0-r8,
r16-r28, gp, pc, and ps. Registers r9-r15 are callee-saved and live
in switch_stack, not pt_regs, so they are not included.

A switch statement maps perf register indices to pt_regs fields since
Alpha's pt_regs layout is non-contiguous (unlike architectures where
direct array indexing works).

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/Kconfig                      |  2 +
 arch/alpha/include/asm/perf_regs.h      |  7 ++
 arch/alpha/include/uapi/asm/perf_regs.h | 34 ++++++++++
 arch/alpha/kernel/Makefile              |  1 +
 arch/alpha/kernel/perf_regs.c           | 86 +++++++++++++++++++++++++
 5 files changed, 130 insertions(+)
 create mode 100644 arch/alpha/include/asm/perf_regs.h
 create mode 100644 arch/alpha/include/uapi/asm/perf_regs.h
 create mode 100644 arch/alpha/kernel/perf_regs.c

diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
index bda8443a7323..74d13a29b8a9 100644
--- ./arch/alpha/Kconfig
+++ ./arch/alpha/Kconfig
@@ -31,6 +31,8 @@ config ALPHA
 	select HAVE_PAGE_SIZE_8KB
 	select HAVE_PCSPKR_PLATFORM
 	select HAVE_PERF_EVENTS
+	select HAVE_PERF_REGS
+	select HAVE_PERF_USER_STACK_DUMP
 	select NEED_DMA_MAP_STATE
 	select NEED_SG_DMA_LENGTH
 	select GENERIC_IRQ_PROBE
diff --git ./arch/alpha/include/asm/perf_regs.h ./arch/alpha/include/asm/perf_regs.h
new file mode 100644
index 000000000000..6045da1a2a4f
--- /dev/null
+++ ./arch/alpha/include/asm/perf_regs.h
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_ALPHA_PERF_REGS_H
+#define _ASM_ALPHA_PERF_REGS_H
+
+#include <uapi/asm/perf_regs.h>
+
+#endif /* _ASM_ALPHA_PERF_REGS_H */
diff --git ./arch/alpha/include/uapi/asm/perf_regs.h ./arch/alpha/include/uapi/asm/perf_regs.h
new file mode 100644
index 000000000000..afeb6a1584cd
--- /dev/null
+++ ./arch/alpha/include/uapi/asm/perf_regs.h
@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _UAPI_ASM_ALPHA_PERF_REGS_H
+#define _UAPI_ASM_ALPHA_PERF_REGS_H
+
+enum perf_event_alpha_regs {
+	PERF_REG_ALPHA_R0,
+	PERF_REG_ALPHA_R1,
+	PERF_REG_ALPHA_R2,
+	PERF_REG_ALPHA_R3,
+	PERF_REG_ALPHA_R4,
+	PERF_REG_ALPHA_R5,
+	PERF_REG_ALPHA_R6,
+	PERF_REG_ALPHA_R7,
+	PERF_REG_ALPHA_R8,
+	PERF_REG_ALPHA_R16,
+	PERF_REG_ALPHA_R17,
+	PERF_REG_ALPHA_R18,
+	PERF_REG_ALPHA_R19,
+	PERF_REG_ALPHA_R20,
+	PERF_REG_ALPHA_R21,
+	PERF_REG_ALPHA_R22,
+	PERF_REG_ALPHA_R23,
+	PERF_REG_ALPHA_R24,
+	PERF_REG_ALPHA_R25,
+	PERF_REG_ALPHA_R26,
+	PERF_REG_ALPHA_R27,
+	PERF_REG_ALPHA_R28,
+	PERF_REG_ALPHA_GP,
+	PERF_REG_ALPHA_PC,
+	PERF_REG_ALPHA_PS,
+	PERF_REG_ALPHA_MAX,
+};
+
+#endif /* _UAPI_ASM_ALPHA_PERF_REGS_H */
diff --git ./arch/alpha/kernel/Makefile ./arch/alpha/kernel/Makefile
index 4ea5c189e60e..0c04b89676ed 100644
--- ./arch/alpha/kernel/Makefile
+++ ./arch/alpha/kernel/Makefile
@@ -18,6 +18,7 @@ obj-$(CONFIG_PCI)	+= pci.o pci_iommu.o pci-sysfs.o
 obj-$(CONFIG_SRM_ENV)	+= srm_env.o
 obj-$(CONFIG_MODULES)	+= module.o
 obj-$(CONFIG_PERF_EVENTS) += perf_event.o
+obj-$(CONFIG_HAVE_PERF_REGS) += perf_regs.o
 obj-$(CONFIG_RTC_DRV_ALPHA) += rtc.o
 obj-$(CONFIG_AUDIT)	+= audit.o
 
diff --git ./arch/alpha/kernel/perf_regs.c ./arch/alpha/kernel/perf_regs.c
new file mode 100644
index 000000000000..e15081ac95e0
--- /dev/null
+++ ./arch/alpha/kernel/perf_regs.c
@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/perf_event.h>
+#include <asm/perf_regs.h>
+#include <asm/ptrace.h>
+
+u64 perf_reg_value(struct pt_regs *regs, int idx)
+{
+	switch (idx) {
+	case PERF_REG_ALPHA_R0:
+		return regs->r0;
+	case PERF_REG_ALPHA_R1:
+		return regs->r1;
+	case PERF_REG_ALPHA_R2:
+		return regs->r2;
+	case PERF_REG_ALPHA_R3:
+		return regs->r3;
+	case PERF_REG_ALPHA_R4:
+		return regs->r4;
+	case PERF_REG_ALPHA_R5:
+		return regs->r5;
+	case PERF_REG_ALPHA_R6:
+		return regs->r6;
+	case PERF_REG_ALPHA_R7:
+		return regs->r7;
+	case PERF_REG_ALPHA_R8:
+		return regs->r8;
+	case PERF_REG_ALPHA_R16:
+		return regs->r16;
+	case PERF_REG_ALPHA_R17:
+		return regs->r17;
+	case PERF_REG_ALPHA_R18:
+		return regs->r18;
+	case PERF_REG_ALPHA_R19:
+		return regs->r19;
+	case PERF_REG_ALPHA_R20:
+		return regs->r20;
+	case PERF_REG_ALPHA_R21:
+		return regs->r21;
+	case PERF_REG_ALPHA_R22:
+		return regs->r22;
+	case PERF_REG_ALPHA_R23:
+		return regs->r23;
+	case PERF_REG_ALPHA_R24:
+		return regs->r24;
+	case PERF_REG_ALPHA_R25:
+		return regs->r25;
+	case PERF_REG_ALPHA_R26:
+		return regs->r26;
+	case PERF_REG_ALPHA_R27:
+		return regs->r27;
+	case PERF_REG_ALPHA_R28:
+		return regs->r28;
+	case PERF_REG_ALPHA_GP:
+		return regs->gp;
+	case PERF_REG_ALPHA_PC:
+		return regs->pc;
+	case PERF_REG_ALPHA_PS:
+		return regs->ps;
+	default:
+		WARN_ON_ONCE(1);
+		return 0;
+	}
+}
+
+#define REG_RESERVED (~((1ULL << PERF_REG_ALPHA_MAX) - 1))
+
+int perf_reg_validate(u64 mask)
+{
+	if (!mask || mask & REG_RESERVED)
+		return -EINVAL;
+
+	return 0;
+}
+
+u64 perf_reg_abi(struct task_struct *task)
+{
+	return PERF_SAMPLE_REGS_ABI_64;
+}
+
+void perf_get_regs_user(struct perf_regs *regs_user,
+			struct pt_regs *regs)
+{
+	regs_user->regs = task_pt_regs(current);
+	regs_user->abi = perf_reg_abi(current);
+}
-- 
2.54.0

Re: [PATCH 22/24] alpha: add HAVE_PERF_REGS and HAVE_PERF_USER_STACK_DUMP support

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:51 PM Matt Turner <mattst88@gmail.com> wrote:
>
> Implement the perf register sampling interface for Alpha. This enables
> perf to capture register state and user stack dumps with samples,
> supporting --call-graph dwarf.
>
> The perf_regs enum exposes the registers available in pt_regs: r0-r8,
> r16-r28, gp, pc, and ps. Registers r9-r15 are callee-saved and live
> in switch_stack, not pt_regs, so they are not included.
>
> A switch statement maps perf register indices to pt_regs fields since
> Alpha's pt_regs layout is non-contiguous (unlike architectures where
> direct array indexing works).
>

I tested this on an Alpha UP2000. Basic perf recording works, but
user-register and user-stack sampling still appear to need some
additional work.

`perf record --user-regs=?` reports an empty register list, since
tools/perf does not yet provide the Alpha register mask, names, or
IP/SP mappings. Adding DWARF call-graph sampling consequently fails
with EINVAL. I think the corresponding tools/perf support could be
added as a separate patch in this series.

There also appears to be one kernel-side issue with user-stack
sampling. The generic code obtains the stack pointer through
user_stack_pointer(regs), which returns regs->usp on Alpha.

Alpha already has alpha_snapshot_usp(), which initializes this field
for user-mode register frames, but it is currently local to traps.c
and is only called from do_entArith() and do_entIF(). The interrupt
entry path through do_entInt() does not call it.

Perhaps alpha_snapshot_usp() could be moved to a shared header and
called near the beginning of do_entInt(), before dispatching the
interrupt. That would ensure that perf_irq() receives a valid
regs->usp for interrupts taken from userspace, without adding this
work to the SAVE_ALL assembly macro.

The perf register ABI also appears to be missing SP. This could be
provided using current_user_stack_pointer(), as in the older Alpha
implementation.

I have some older Alpha kernel and tools/perf patches which implement
similar support. They target an older API, but I will send them
off-list in case any of the code is useful. Please feel free to reuse
or adapt whatever helps.

Regards,
Magnus

[PATCH 23/24] alpha: select SPARSE_IRQ

[Matt Turner]

NR_IRQS on Alpha is sized for the largest configuration each platform
supports, and for Marvel that is 32 PIDs, or 32784 interrupts.  Without
SPARSE_IRQ that becomes a static irq_desc[] array of 12.6 MB in .data,
carried by every Marvel and every generic kernel regardless of how many
interrupts the machine actually has.  A real ES47 uses 87 of them.

That is not just wasted memory, it constrains where the kernel can be
loaded.  The image links at a fixed 0xfffffc0001010000, just above the
console's low memory reservation, and with memory striping enabled the
console leaves only about 16 MB of usable low memory before the rest is
relocated to an interleaved aperture.  A 12.6 MB array of mostly unused
interrupt descriptors is the difference between fitting and not.

Alpha already goes through irq_to_desc() rather than indexing irq_desc[]
directly, so nothing stands in the way.  The platforms do wire up their
interrupts by number, though, which needs the descriptors to exist by
then, so provide arch_probe_nr_irqs() returning the machine vector's
count instead of taking the NR_IRQS_LEGACY default.  Without it every
interrupt above 15 would have no descriptor and the handler setup would
be silently dropped.

Tested on an ES47 (Marvel, 2 EV7z): boots with all device interrupts
working, and .data drops by 12.6 MB, from 15.7 MB to 3.1 MB.
---
 arch/alpha/Kconfig            |  1 +
 arch/alpha/kernel/irq_alpha.c | 13 +++++++++++++
 2 files changed, 14 insertions(+)

diff --git ./arch/alpha/Kconfig ./arch/alpha/Kconfig
index 74d13a29b8a9..06c3e55f01f2 100644
--- ./arch/alpha/Kconfig
+++ ./arch/alpha/Kconfig
@@ -62,6 +62,7 @@ config ALPHA
 	select CPU_NO_EFFICIENT_FFS if !ALPHA_EV67
 	select MMU_GATHER_NO_RANGE
 	select MMU_GATHER_RCU_TABLE_FREE
+	select SPARSE_IRQ
 	select SPARSEMEM_EXTREME if SPARSEMEM
 	select SYSCTL_EXCEPTION_TRACE
 	select ZONE_DMA
diff --git ./arch/alpha/kernel/irq_alpha.c ./arch/alpha/kernel/irq_alpha.c
index 1b799aafb7dc..3274568d6d52 100644
--- ./arch/alpha/kernel/irq_alpha.c
+++ ./arch/alpha/kernel/irq_alpha.c
@@ -148,6 +148,19 @@ common_init_isa_dma(void)
 	outb(0, DMA2_CLR_MASK_REG);
 }
 
+/*
+ * The platforms wire up their interrupts by calling into the generic irq
+ * code with fixed interrupt numbers, so the descriptors have to exist by
+ * then.  Preallocate the machine's full complement rather than take the
+ * NR_IRQS_LEGACY default, which would leave everything above IRQ 15
+ * without a descriptor and silently drop the handler setup.
+ */
+int __init
+arch_probe_nr_irqs(void)
+{
+	return alpha_mv.nr_irqs;
+}
+
 void __init
 init_IRQ(void)
 {
-- 
2.54.0

Re: [PATCH 23/24] alpha: select SPARSE_IRQ

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:52 PM Matt Turner <mattst88@gmail.com> wrote:
>
> NR_IRQS on Alpha is sized for the largest configuration each platform
> supports, and for Marvel that is 32 PIDs, or 32784 interrupts.  Without
> SPARSE_IRQ that becomes a static irq_desc[] array of 12.6 MB in .data,
> carried by every Marvel and every generic kernel regardless of how many
> interrupts the machine actually has.  A real ES47 uses 87 of them.
>
> That is not just wasted memory, it constrains where the kernel can be
> loaded.  The image links at a fixed 0xfffffc0001010000, just above the
> console's low memory reservation, and with memory striping enabled the
> console leaves only about 16 MB of usable low memory before the rest is
> relocated to an interleaved aperture.  A 12.6 MB array of mostly unused
> interrupt descriptors is the difference between fitting and not.
>
> Alpha already goes through irq_to_desc() rather than indexing irq_desc[]
> directly, so nothing stands in the way.  The platforms do wire up their
> interrupts by number, though, which needs the descriptors to exist by
> then, so provide arch_probe_nr_irqs() returning the machine vector's
> count instead of taking the NR_IRQS_LEGACY default.  Without it every
> interrupt above 15 would have no descriptor and the handler setup would
> be silently dropped.
>
> Tested on an ES47 (Marvel, 2 EV7z): boots with all device interrupts
> working, and .data drops by 12.6 MB, from 15.7 MB to 3.1 MB.
> ---
>  arch/alpha/Kconfig            |  1 +
>  arch/alpha/kernel/irq_alpha.c | 13 +++++++++++++
>  2 files changed, 14 insertions(+)
>

This patch appears to be missing your Signed-off-by tag.

Tested on a two-CPU UP2000 with CONFIG_SPARSE_IRQ=y. The kernel booted
successfully and created IRQ descriptors 0 through 63. SCSI devices on
IRQs 19 and 27 and Ethernet on IRQ 43 operated normally, with their
interrupt counts increasing. I observed no IRQ setup failures or other
IRQ-related warnings.

Regards

Magnus

[PATCH 24/24] alpha: add TRACE_IRQFLAGS_SUPPORT

[Matt Turner]

Instrument the entry/exit assembly to track hardirq state for lockdep.

TRACE_IRQS_OFF is called after SAVE_ALL at each exception/interrupt
entry point and at syscall entry.  TRACE_IRQS_ON is called at
restore_all before returning to userspace, where PAL_rti will restore
the user IPL (re-enabling interrupts).

The function call clobbers caller-saved registers, so the
TRACE_IRQS_OFF macro reloads $0 and $16-$18 from the pt_regs frame.
$8 (current_thread_info) is preserved because it is declared as a
global register variable.

Together with the previously added STACKTRACE_SUPPORT and
LOCKDEP_SUPPORT, this enables LOCK_DEBUGGING_SUPPORT on Alpha.

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Matt Turner <mattst88@gmail.com>
---
 arch/alpha/kernel/entry.S | 54 +++++++++++++++++++++++++++++++++------
 1 file changed, 46 insertions(+), 8 deletions(-)

diff --git ./arch/alpha/kernel/entry.S ./arch/alpha/kernel/entry.S
index 9f2608de2544..ed5df48503d0 100644
--- ./arch/alpha/kernel/entry.S
+++ ./arch/alpha/kernel/entry.S
@@ -241,6 +241,36 @@
 	.cfi_adjust_cfa_offset	-SWITCH_STACK_SIZE
 .endm
 
+/*
+ * Trace hardirq state changes for lockdep.  TRACE_IRQS_OFF is called
+ * after SAVE_ALL at each entry point where PALcode enters with IPL
+ * raised (interrupts disabled).  TRACE_IRQS_ON is called before
+ * returning to userspace, where PAL_rti will restore the user IPL.
+ *
+ * The function call clobbers caller-saved registers; $8 is preserved
+ * because it is declared as a global register variable for
+ * current_thread_info.  We reload $0 and $16-$18 from the pt_regs
+ * frame that SAVE_ALL created, since entry points pass those to their
+ * C handlers.
+ */
+.macro TRACE_IRQS_OFF
+#ifdef CONFIG_TRACE_IRQFLAGS
+	jsr	$26, trace_hardirqs_off
+	ldgp	$gp, 0($26)
+	ldq	$0, 0($sp)
+	ldq	$16, 160($sp)
+	ldq	$17, 168($sp)
+	ldq	$18, 176($sp)
+#endif
+.endm
+
+.macro TRACE_IRQS_ON
+#ifdef CONFIG_TRACE_IRQFLAGS
+	jsr	$26, trace_hardirqs_on
+	ldgp	$gp, 0($26)
+#endif
+.endm
+
 /*
  * Non-syscall kernel entry points.
  */
@@ -248,8 +278,9 @@
 CFI_START_OSF_FRAME entInt
 	SAVE_ALL
 	lda	$8, 0x3fff
-	lda	$26, ret_from_sys_call
 	bic	$sp, $8, $8
+	TRACE_IRQS_OFF
+	lda	$26, ret_from_sys_call
 	mov	$sp, $19
 	jsr	$31, do_entInt
 CFI_END_OSF_FRAME entInt
@@ -257,14 +288,18 @@ CFI_END_OSF_FRAME entInt
 CFI_START_OSF_FRAME entArith
 	SAVE_ALL
 	lda	$8, 0x3fff
-	lda	$26, ret_from_sys_call
 	bic	$sp, $8, $8
+	TRACE_IRQS_OFF
+	lda	$26, ret_from_sys_call
 	mov	$sp, $18
 	jsr	$31, do_entArith
 CFI_END_OSF_FRAME entArith
 
 CFI_START_OSF_FRAME entMM
 	SAVE_ALL
+	lda	$8, 0x3fff
+	bic	$sp, $8, $8
+	TRACE_IRQS_OFF
 /* save $9 - $15 so the inline exception code can manipulate them.  */
 	subq	$sp, 64, $sp
 	.cfi_adjust_cfa_offset	64
@@ -284,8 +319,6 @@ CFI_START_OSF_FRAME entMM
 	.cfi_rel_offset	$15, 48
 	addq	$sp, 64, $19
 /* handle the fault */
-	lda	$8, 0x3fff
-	bic	$sp, $8, $8
 	jsr	$26, do_page_fault
 /* reload the registers after the exception code played.  */
 	ldq	$9, 0($sp)
@@ -311,8 +344,9 @@ CFI_END_OSF_FRAME entMM
 CFI_START_OSF_FRAME entIF
 	SAVE_ALL
 	lda	$8, 0x3fff
-	lda	$26, ret_from_sys_call
 	bic	$sp, $8, $8
+	TRACE_IRQS_OFF
+	lda	$26, ret_from_sys_call
 	mov	$sp, $17
 	jsr	$31, do_entIF
 CFI_END_OSF_FRAME entIF
@@ -451,6 +485,9 @@ entUnaUser:
 	.cfi_restore	$0
 	.cfi_adjust_cfa_offset	-256
 	SAVE_ALL		/* setup normal kernel stack */
+	lda	$8, 0x3fff
+	bic	$sp, $8, $8
+	TRACE_IRQS_OFF
 	lda	$sp, -64($sp)
 	.cfi_adjust_cfa_offset	64
 	stq	$9, 0($sp)
@@ -467,9 +504,7 @@ entUnaUser:
 	.cfi_rel_offset	$13, 32
 	.cfi_rel_offset	$14, 40
 	.cfi_rel_offset	$15, 48
-	lda	$8, 0x3fff
 	addq	$sp, 64, $19
-	bic	$sp, $8, $8
 	jsr	$26, do_entUnaUser
 	ldq	$9, 0($sp)
 	ldq	$10, 8($sp)
@@ -493,8 +528,9 @@ CFI_END_OSF_FRAME entUna
 CFI_START_OSF_FRAME entDbg
 	SAVE_ALL
 	lda	$8, 0x3fff
-	lda	$26, ret_from_sys_call
 	bic	$sp, $8, $8
+	TRACE_IRQS_OFF
+	lda	$26, ret_from_sys_call
 	mov	$sp, $16
 	jsr	$31, do_entDbg
 CFI_END_OSF_FRAME entDbg
@@ -543,6 +579,7 @@ entSys:
 
 	lda	$8, 0x3fff
 	bic	$sp, $8, $8
+	TRACE_IRQS_OFF
 	lda	$4, NR_syscalls($31)
 	stq	$16, SP_OFF+24($sp)
 	lda	$5, sys_call_table
@@ -586,6 +623,7 @@ ret_to_user:
 	and	$17, _TIF_WORK_MASK, $2
 	bne	$2, work_pending
 restore_all:
+	TRACE_IRQS_ON
 	ldl	$2, TI_STATUS($8)
 	and	$2, TS_SAVED_FP | TS_RESTORE_FP, $3
 	bne	$3, restore_fpu
-- 
2.54.0

Re: [PATCH 24/24] alpha: add TRACE_IRQFLAGS_SUPPORT

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:52 PM Matt Turner <mattst88@gmail.com> wrote:
>
> Instrument the entry/exit assembly to track hardirq state for lockdep.
>
> TRACE_IRQS_OFF is called after SAVE_ALL at each exception/interrupt
> entry point and at syscall entry.  TRACE_IRQS_ON is called at
> restore_all before returning to userspace, where PAL_rti will restore
> the user IPL (re-enabling interrupts).
>
> The function call clobbers caller-saved registers, so the
> TRACE_IRQS_OFF macro reloads $0 and $16-$18 from the pt_regs frame.
> $8 (current_thread_info) is preserved because it is declared as a
> global register variable.
>
> Together with the previously added STACKTRACE_SUPPORT and
> LOCKDEP_SUPPORT, this enables LOCK_DEBUGGING_SUPPORT on Alpha.
>
> Assisted-by: Claude:claude-opus-4-6
> Signed-off-by: Matt Turner <mattst88@gmail.com>

I think this patch needs to be rebased on top of Alpha GENERIC_ENTRY
v5. Both patches are based on entry.S blob 9f2608de2544 and modify the
same entry and return paths, so they cannot currently be applied in
either order.

With GENERIC_ENTRY, the syscall IRQ-state transitions are already
handled by syscall_enter_from_user_mode_randomize_stack() and
syscall_exit_to_user_mode(). Non-syscall user returns go through
exit_to_user_mode(), which also performs the final hardirqs-on
transition.

The interrupt path already calls raw_local_irq_disable() and updates
the lockdep state in do_entInt(), while kernel-mode PAL returns retain
the Alpha-specific lockdep_on_restore() handling.

Adding TRACE_IRQS_OFF to entSys and TRACE_IRQS_ON to restore_all would
therefore duplicate the generic-entry transitions. I think the patch
should instead be rebased and limited to any entry paths which remain
uncovered after GENERIC_ENTRY v5 is applied.

Keeping these transitions in the generic C entry helpers where
possible would also avoid additional register-save and restore logic
in entry.S.

Regards,
Magnus

Re: [PATCH 00/24] alpha: catch up on architecture Kconfig options

[Magnus Lindholm]

Hi Matt,

On Tue, Sep 1, 2026 at 5:50 PM Matt Turner <mattst88@gmail.com> wrote:
>
> Alpha is missing a long list of Kconfig options that other architectures
> have picked up over the years, some of them for no better reason than
> nobody having gone through the list.  I diffed the select statements in
> every other arch/*/Kconfig against arch/alpha/Kconfig and worked through
> what turned up.  This series is the result: two fixes it depends on, and
> the options that are either free or close to it.
>
> The patches are ordered from least to most contentious, so the front of
> the series can be applied on its own if the tail needs discussion.
>
> Patches 1-2 are fixes.  arch_irqs_disabled_flags() only reported
> interrupts as disabled at IPL_MAX, but PALcode enters handlers at the
> IPL of the interrupt being delivered, so a device or timer handler
> answered that interrupts were enabled.  handle_irq() also called
> irq_to_desc() before irq_enter(), running generic code with the preempt
> count still saying task context and RCU not yet watching.  Both matter on
> their own; patches 23 and 24 are what made them visible.
>
> Patches 3-11 are one-line selects with no Alpha code behind them:
> instrumentation (UBSAN, gcov, kmemleak), EDAC, and four properties Alpha
> has always had but never declared (LL/SC atomics, hardware multiply,
> __int128, the existing asm/compiler.h, and the non-overlapping user and
> kernel address spaces).
>
> Patches 12-17 add a small amount of code: an empty thread_struct
> whitelist, _PAGE_SPECIAL on a free PTE bit, the page table check helpers,
> and then the three things that follow from those - the page table helper
> self test, lockless GUP, and the early memtest.  Note that early_memtest()
> is called from arch_mm_preinit() rather than paging_init(), because Alpha
> calls paging_init() from setup_arch(), before parse_early_param() has seen
> the memtest= option.
>
> Patches 18-20 change something visible.  Unhandled user faults now print
> the usual message under the debug.exception-trace sysctl.  .eh_frame is
> discarded: gcc emits it for Alpha regardless of
> -fno-asynchronous-unwind-tables, it was allocated in the loaded image, and
> nothing consumes it, since the stack trace code scans for text addresses
> rather than unwinding DWARF.  That is worth about 1.1MB.  With that and
> the relocation sections placed explicitly, the kernel links with no
> orphans left, so the last of the three asks the linker to say so.
>
> Patches 21-24 are the ones I expect to draw comment.  Patch 22 adds a
> uapi header, so the perf register numbering is an ABI decision.  Patch 23
> is SPARSE_IRQ: without it Marvel carries a 12.6MB static irq_desc[] in
> .data for 32768 possible interrupts, of which a real ES47 uses 87, and
> the kernel links at a fixed address just above the console reservation
> where that 12.6MB is the difference between fitting and not.  Patch 24
> instruments the entry assembly for lockdep hardirq tracking.
>
> Tested with gcc 17 under QEMU (-M clipper -smp 2, an ALPHA_GENERIC build)
> with PROVE_LOCKING enabled: no splats, early_memtest passes all four
> patterns over the free memblock ranges with nothing reserved,
> debug_vm_pgtable validates with no warning, a vmsplice() of an anonymous
> mapping through pin_user_pages_fast() returns the right data, and an
> unhandled SIGSEGV prints the new trace line.  Patch 23 was tested on an
> AlphaServer ES47.
>
> Not included, and worth mentioning: ARCH_HAS_KCOV.  A kernel with
> KCOV_INSTRUMENT_ALL boots and runs, but CONFIG_KCOV_SELFTEST panics.  The
> self test deliberately arms kcov with no coverage area so that any
> instrumented function reached from interrupt context faults, checking
> that nothing escapes the window before the preempt count says hardirq.
> On Alpha something does.  Patch 2 fixes one such site; the panic survives
> it, so the entry paths need an audit first.
>

Thanks for taking the time to do this! This is a nice collection of patches.
I've started on the review and testing, I will keep at it.
As general feedback for the series, I noticed that several of the
corresponding architecture feature matrices still list Alpha as TODO.
The Alpha entries should be changed to "ok" for:

  ARCH_HAS_GCOV_PROFILE_ALL
  HAVE_DEBUG_KMEMLEAK
  ARCH_HAS_PTE_SPECIAL
  ARCH_HAS_DEBUG_VM_PGTABLE
  HAVE_PERF_REGS
  HAVE_PERF_USER_STACK_DUMP

These correspond to patches 4, 5, 13, 15, and 22.  It would probably be
best to include each documentation update in the patch which enables the
corresponding feature.

It would also be helpful if the next revision were rebased onto
v7.3-rc1 and applied cleanly on top of my Alpha GENERIC_ENTRY v5 series.
I am currently testing only the patches which applied successfully.

Alpha GENERIC_ENTRY v5 series is available here:
https://lore.kernel.org/linux-alpha/20260902184058.198679-1-linmag7@gmail.com/T/#t

Regards,
Magnus

Re: [PATCH 00/24] alpha: catch up on architecture Kconfig options

[Matt Turner]

On Wed, Sep 2, 2026 at 2:54 PM Magnus Lindholm <linmag7@gmail.com> wrote:
>
> Hi Matt,
>
> On Tue, Sep 1, 2026 at 5:50 PM Matt Turner <mattst88@gmail.com> wrote:
> >
> > Alpha is missing a long list of Kconfig options that other architectures
> > have picked up over the years, some of them for no better reason than
> > nobody having gone through the list.  I diffed the select statements in
> > every other arch/*/Kconfig against arch/alpha/Kconfig and worked through
> > what turned up.  This series is the result: two fixes it depends on, and
> > the options that are either free or close to it.
> >
> > The patches are ordered from least to most contentious, so the front of
> > the series can be applied on its own if the tail needs discussion.
> >
> > Patches 1-2 are fixes.  arch_irqs_disabled_flags() only reported
> > interrupts as disabled at IPL_MAX, but PALcode enters handlers at the
> > IPL of the interrupt being delivered, so a device or timer handler
> > answered that interrupts were enabled.  handle_irq() also called
> > irq_to_desc() before irq_enter(), running generic code with the preempt
> > count still saying task context and RCU not yet watching.  Both matter on
> > their own; patches 23 and 24 are what made them visible.
> >
> > Patches 3-11 are one-line selects with no Alpha code behind them:
> > instrumentation (UBSAN, gcov, kmemleak), EDAC, and four properties Alpha
> > has always had but never declared (LL/SC atomics, hardware multiply,
> > __int128, the existing asm/compiler.h, and the non-overlapping user and
> > kernel address spaces).
> >
> > Patches 12-17 add a small amount of code: an empty thread_struct
> > whitelist, _PAGE_SPECIAL on a free PTE bit, the page table check helpers,
> > and then the three things that follow from those - the page table helper
> > self test, lockless GUP, and the early memtest.  Note that early_memtest()
> > is called from arch_mm_preinit() rather than paging_init(), because Alpha
> > calls paging_init() from setup_arch(), before parse_early_param() has seen
> > the memtest= option.
> >
> > Patches 18-20 change something visible.  Unhandled user faults now print
> > the usual message under the debug.exception-trace sysctl.  .eh_frame is
> > discarded: gcc emits it for Alpha regardless of
> > -fno-asynchronous-unwind-tables, it was allocated in the loaded image, and
> > nothing consumes it, since the stack trace code scans for text addresses
> > rather than unwinding DWARF.  That is worth about 1.1MB.  With that and
> > the relocation sections placed explicitly, the kernel links with no
> > orphans left, so the last of the three asks the linker to say so.
> >
> > Patches 21-24 are the ones I expect to draw comment.  Patch 22 adds a
> > uapi header, so the perf register numbering is an ABI decision.  Patch 23
> > is SPARSE_IRQ: without it Marvel carries a 12.6MB static irq_desc[] in
> > .data for 32768 possible interrupts, of which a real ES47 uses 87, and
> > the kernel links at a fixed address just above the console reservation
> > where that 12.6MB is the difference between fitting and not.  Patch 24
> > instruments the entry assembly for lockdep hardirq tracking.
> >
> > Tested with gcc 17 under QEMU (-M clipper -smp 2, an ALPHA_GENERIC build)
> > with PROVE_LOCKING enabled: no splats, early_memtest passes all four
> > patterns over the free memblock ranges with nothing reserved,
> > debug_vm_pgtable validates with no warning, a vmsplice() of an anonymous
> > mapping through pin_user_pages_fast() returns the right data, and an
> > unhandled SIGSEGV prints the new trace line.  Patch 23 was tested on an
> > AlphaServer ES47.
> >
> > Not included, and worth mentioning: ARCH_HAS_KCOV.  A kernel with
> > KCOV_INSTRUMENT_ALL boots and runs, but CONFIG_KCOV_SELFTEST panics.  The
> > self test deliberately arms kcov with no coverage area so that any
> > instrumented function reached from interrupt context faults, checking
> > that nothing escapes the window before the preempt count says hardirq.
> > On Alpha something does.  Patch 2 fixes one such site; the panic survives
> > it, so the entry paths need an audit first.
> >
>
> Thanks for taking the time to do this! This is a nice collection of patches.
> I've started on the review and testing, I will keep at it.
> As general feedback for the series, I noticed that several of the
> corresponding architecture feature matrices still list Alpha as TODO.
> The Alpha entries should be changed to "ok" for:
>
>   ARCH_HAS_GCOV_PROFILE_ALL
>   HAVE_DEBUG_KMEMLEAK
>   ARCH_HAS_PTE_SPECIAL
>   ARCH_HAS_DEBUG_VM_PGTABLE
>   HAVE_PERF_REGS
>   HAVE_PERF_USER_STACK_DUMP
>
> These correspond to patches 4, 5, 13, 15, and 22.  It would probably be
> best to include each documentation update in the patch which enables the
> corresponding feature.

Oh, definitely. Thanks for catching that.

> It would also be helpful if the next revision were rebased onto
> v7.3-rc1 and applied cleanly on top of my Alpha GENERIC_ENTRY v5 series.
> I am currently testing only the patches which applied successfully.
>
> Alpha GENERIC_ENTRY v5 series is available here:
> https://lore.kernel.org/linux-alpha/20260902184058.198679-1-linmag7@gmail.com/T/#t

Perfect, I will do it!