[PATCH Dovetail 6.17 v3 0/4] dovetail: Add support for hyper-v as hypervisor

[PATCH Dovetail 6.17 v3 0/4] dovetail: Add support for hyper-v as hypervisor

[Florian Bezdeka]

Hi all,

with this series applied dovetail is successfully booting up on a
Windows host using the Hyper-V hypervisor as virtualization platform.

You won't get any RT guarantees - that's clear - but it helps to test
non-RT stuff using a dovetail enabled kernel on such a platform.

The following config knobs were turned on during testing:
  - CONFIG_HYPERV
  - CONFIG_HYPERV_NET
  - CONFIG_HYPERV_KEYBOARD
  - CONFIG_HYPERV_TIMER
  - CONFIG_HYPERV_UTILS
  - CONFIG_HYPERV_BALLOON
  - CONFIG_HYPERV_IOMMU
  - CONFIG_HYPERV_STORAGE

Best regards,
Florian

Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Philippe Gerum <rpm@xenomai.org>

Signed-off-by: Florian Bezdeka <florian.bezdeka@siemens.com>
---
Changes in v3:
- Rebased on top of Dovetail 6.17 rc
- Set patch prefix to 6.17
- Adress review comments from Philippe, basically git log update of
  patch 1
- Link to v2: https://lore.kernel.org/r/20250602-flo-add-hyperv-support-for-6-15-v2-0-f1c802b1aba3@siemens.com

Changes in v2:
- Added correct "Dovetail 6.16" prefix
- Updated Cc list
- Link to v1: https://lore.kernel.org/r/20250602-flo-add-hyperv-support-for-6-15-v1-0-449e6c20debd@siemens.com

---
Florian Bezdeka (4):
      clocksource/hyper-v: irq_pipeline: Enable pipelined clock events
      x86: irq_pipeline: Implement inband handler for hyper-v specific vectors
      hyper-v: x86: dovetail: Close race window in PV spinlocks
      x86: irq_pipeline: Allow CONFIG_HYPERV in combination with CONFIG_DOVETAIL

 arch/x86/hyperv/hv_spinlock.c      |  4 ++--
 arch/x86/kernel/irq_pipeline.c     |  9 +++++++++
 drivers/clocksource/hyperv_timer.c | 34 +++++++++++++++++++++++++++++++++-
 drivers/hv/Kconfig                 |  2 +-
 4 files changed, 45 insertions(+), 4 deletions(-)
---
base-commit: e978823786e09bd5842045153f99af39ffebbcfc
change-id: 20250602-flo-add-hyperv-support-for-6-15-37378bd63fe1

Best regards,
-- 
Florian Bezdeka <florian.bezdeka@siemens.com>

[PATCH Dovetail 6.17 v3 1/4] clocksource/hyper-v: irq_pipeline: Enable pipelined clock events

[Florian Bezdeka]

Make the clock event around the STIMER0 pipeline safe. The
implementation is following the same pattern that we already have in
place for the x86 LAPIC interrupt / clock event.

To get the proxy tick working we need to link the hyperv clock event
device with the STIMER0 vector. This part is also following the pattern
of the x86 lapic interrupt. Both have a fixed arch specific vector
assigned.

Signed-off-by: Florian Bezdeka <florian.bezdeka@siemens.com>
---
 drivers/clocksource/hyperv_timer.c | 34 +++++++++++++++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index 2edc13ca184e0..0850b0c385a8e 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -26,6 +26,7 @@
 #include <clocksource/hyperv_timer.h>
 #include <hyperv/hvhdk.h>
 #include <asm/mshyperv.h>
+#include <asm/trace/irq_vectors.h>
 
 static struct clock_event_device __percpu *hv_clock_event;
 /* Note: offset can hold negative values after hibernation. */
@@ -53,6 +54,30 @@ static int stimer0_irq = -1;
 static int stimer0_message_sint;
 static __maybe_unused DEFINE_PER_CPU(long, stimer0_evt);
 
+#ifdef CONFIG_IRQ_PIPELINE
+
+#define HV_STIMER_IRQ	apicm_vector_irq(HYPERV_STIMER0_VECTOR)
+
+static irqreturn_t hv_stimer_oob_handler(int irq, void *dev_id)
+{
+	struct clock_event_device *evt = this_cpu_ptr(hv_clock_event);
+
+	trace_local_timer_entry(HYPERV_STIMER0_VECTOR);
+	clockevents_handle_event(evt);
+	trace_local_timer_exit(HYPERV_STIMER0_VECTOR);
+
+	return IRQ_HANDLED;
+}
+
+static struct irqaction hv_stimer_oob_action = {
+	.handler = hv_stimer_oob_handler,
+	.name = "Out-of-band STIMER0 timer interrupt",
+	.flags = IRQF_TIMER | IRQF_PERCPU,
+};
+#else
+#define HV_STIMER_IRQ	-1
+#endif
+
 /*
  * Common code for stimer0 interrupts coming via Direct Mode or
  * as a VMbus message.
@@ -137,8 +162,9 @@ static int hv_stimer_init(unsigned int cpu)
 
 	ce = per_cpu_ptr(hv_clock_event, cpu);
 	ce->name = "Hyper-V clockevent";
-	ce->features = CLOCK_EVT_FEAT_ONESHOT;
+	ce->features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_PIPELINE;
 	ce->cpumask = cpumask_of(cpu);
+	ce->irq = HV_STIMER_IRQ;
 
 	/*
 	 * Lower the rating of the Hyper-V timer in a TDX VM without paravisor,
@@ -305,6 +331,12 @@ int hv_stimer_alloc(bool have_percpu_irqs)
 		hv_remove_stimer0_irq();
 		goto free_clock_event;
 	}
+
+#ifdef CONFIG_IRQ_PIPELINE
+	ret = setup_percpu_irq(HV_STIMER_IRQ, &hv_stimer_oob_action);
+	if (ret)
+		goto free_clock_event;
+#endif
 	return ret;
 
 free_clock_event:

-- 
2.39.5

[PATCH Dovetail 6.17 v3 2/4] x86: irq_pipeline: Implement inband handler for hyper-v specific vectors

[Florian Bezdeka]

Both vectors were already routed to the inband stage but were not
implemented / handled there. We ended up ignoring those IRQs. That
resulted in a boot hang on hyper-v.

Signed-off-by: Florian Bezdeka <florian.bezdeka@siemens.com>
---
 arch/x86/kernel/irq_pipeline.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/x86/kernel/irq_pipeline.c b/arch/x86/kernel/irq_pipeline.c
index 1d6dfc6e95122..d6162310929c6 100644
--- a/arch/x86/kernel/irq_pipeline.c
+++ b/arch/x86/kernel/irq_pipeline.c
@@ -160,6 +160,15 @@ static void do_sysvec_inband(struct irq_desc *desc, struct pt_regs *regs)
 	case POSTED_INTR_NESTED_VECTOR:
 		run_sysvec_on_irqstack_cond(__sysvec_kvm_posted_intr_nested_ipi, regs);
 		break;
+#endif
+#if IS_ENABLED(CONFIG_HYPERV)
+	case HYPERV_REENLIGHTENMENT_VECTOR:
+		run_sysvec_on_irqstack_cond(__sysvec_hyperv_reenlightenment,
+					regs);
+		break;
+	case HYPERV_STIMER0_VECTOR:
+		run_sysvec_on_irqstack_cond(__sysvec_hyperv_stimer0, regs);
+		break;
 #endif
 	case HYPERVISOR_CALLBACK_VECTOR:
 		run_sysvec_on_irqstack_cond(pipeline_hv_callback, regs);

-- 
2.39.5

[PATCH Dovetail 6.17 v3 3/4] hyper-v: x86: dovetail: Close race window in PV spinlocks

[Florian Bezdeka]

Stalling the in-band stage is not enough, we have to disable hard IRQs
to avoid additional instructions between the comparison of the value
and the rdmsrl() - as explained in the comment above.

Signed-off-by: Florian Bezdeka <florian.bezdeka@siemens.com>
---
 arch/x86/hyperv/hv_spinlock.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/hyperv/hv_spinlock.c b/arch/x86/hyperv/hv_spinlock.c
index 81b006601370c..282a0c69c9110 100644
--- a/arch/x86/hyperv/hv_spinlock.c
+++ b/arch/x86/hyperv/hv_spinlock.c
@@ -44,7 +44,7 @@ static void hv_qlock_wait(u8 *byte, u8 val)
 	 * into 'idle' state by the hypervisor and kept in that state for
 	 * an unspecified amount of time.
 	 */
-	local_irq_save(flags);
+	flags = hard_local_irq_save();
 	/*
 	 * Only issue the rdmsrq() when the lock state has not changed.
 	 */
@@ -55,7 +55,7 @@ static void hv_qlock_wait(u8 *byte, u8 val)
 
 		(void)msr_val;
 	}
-	local_irq_restore(flags);
+	hard_local_irq_restore(flags);
 }
 
 /*

-- 
2.39.5

[PATCH Dovetail 6.17 v3 4/4] x86: irq_pipeline: Allow CONFIG_HYPERV in combination with CONFIG_DOVETAIL

[Florian Bezdeka]

No known issues anymore, so we can allow that combination now.

Signed-off-by: Florian Bezdeka <florian.bezdeka@siemens.com>
---
 drivers/hv/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
index cf9cf77ac2187..6c7e76fd1b01e 100644
--- a/drivers/hv/Kconfig
+++ b/drivers/hv/Kconfig
@@ -5,7 +5,7 @@ menu "Microsoft Hyper-V guest support"
 config HYPERV
 	tristate "Microsoft Hyper-V client drivers"
 	depends on ((X86 && X86_LOCAL_APIC && HYPERVISOR_GUEST) \
-		|| (ARM64 && !CPU_BIG_ENDIAN)) && !IRQ_PIPELINE
+		|| (ARM64 && !CPU_BIG_ENDIAN))
 	select PARAVIRT
 	select X86_HV_CALLBACK_VECTOR if X86
 	select OF_EARLY_FLATTREE if OF

-- 
2.39.5

Re: [PATCH Dovetail 6.17 v3 1/4] clocksource/hyper-v: irq_pipeline: Enable pipelined clock events

[Philippe Gerum]

Florian Bezdeka <florian.bezdeka@siemens.com> writes:

> Make the clock event around the STIMER0 pipeline safe. The
> implementation is following the same pattern that we already have in
> place for the x86 LAPIC interrupt / clock event.
>
> To get the proxy tick working we need to link the hyperv clock event
> device with the STIMER0 vector. This part is also following the pattern
> of the x86 lapic interrupt. Both have a fixed arch specific vector
> assigned.
>

Series merged, thanks.

-- 
Philippe.