[PATCH 0/3] Additional refactoring of Hyper-V arch specific code

[PATCH 0/3] Additional refactoring of Hyper-V arch specific code

[Michael Kelley]

This patch set moves additional Hyper-V code under arch/x86 into
arch-neutral hv_common.c where it can be shared by x86 and
and ARM64 implementations.  The move reduces the overall lines
of code across both architectures, and removes code under
arch/ that isn't really architecture-specific.

The code is moved into hv_common.c because it must be
built-in to the kernel image, and not be part of a module.

No functional changes are intended.
Michael Kelley (3):
  Drivers: hv: Make portions of Hyper-V init code be arch neutral
  Drivers: hv: Add arch independent default functions for some Hyper-V
    handlers
  Drivers: hv: Move Hyper-V misc functionality to arch-neutral code

 arch/x86/hyperv/hv_init.c       | 101 +++-----------------
 arch/x86/include/asm/mshyperv.h |   4 -
 arch/x86/kernel/cpu/mshyperv.c  |  24 -----
 drivers/hv/hv_common.c          | 198 ++++++++++++++++++++++++++++++++++++++++
 include/asm-generic/mshyperv.h  |  10 ++
 5 files changed, 219 insertions(+), 118 deletions(-)

-- 
1.8.3.1

[PATCH 1/3] Drivers: hv: Make portions of Hyper-V init code be arch neutral

[Michael Kelley]

The code to allocate and initialize the hv_vp_index array is
architecture neutral. Similarly, the code to allocate and
populate the hypercall input and output arg pages is architecture
neutral.  Move both sets of code out from arch/x86 and into
utility functions in drivers/hv/hv_common.c that can be shared
by Hyper-V initialization on ARM64.

No functional changes. However, the allocation of the hypercall
input and output arg pages is done differently so that the
size is always the Hyper-V page size, even if not the same as
the guest page size (such as with ARM64's 64K page size).

Signed-off-by: Michael Kelley <mikelley@microsoft.com>
---
 arch/x86/hyperv/hv_init.c       |  91 +++-------------------------
 arch/x86/include/asm/mshyperv.h |   4 --
 arch/x86/kernel/cpu/mshyperv.c  |   7 ---
 drivers/hv/hv_common.c          | 131 ++++++++++++++++++++++++++++++++++++++++
 include/asm-generic/mshyperv.h  |  10 +++
 5 files changed, 151 insertions(+), 92 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 6952e21..5cc0c0f 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -39,48 +39,17 @@
 /* Storage to save the hypercall page temporarily for hibernation */
 static void *hv_hypercall_pg_saved;
 
-u32 *hv_vp_index;
-EXPORT_SYMBOL_GPL(hv_vp_index);
-
 struct hv_vp_assist_page **hv_vp_assist_page;
 EXPORT_SYMBOL_GPL(hv_vp_assist_page);
 
-void  __percpu **hyperv_pcpu_input_arg;
-EXPORT_SYMBOL_GPL(hyperv_pcpu_input_arg);
-
-void  __percpu **hyperv_pcpu_output_arg;
-EXPORT_SYMBOL_GPL(hyperv_pcpu_output_arg);
-
-u32 hv_max_vp_index;
-EXPORT_SYMBOL_GPL(hv_max_vp_index);
-
 static int hv_cpu_init(unsigned int cpu)
 {
-	u64 msr_vp_index;
 	struct hv_vp_assist_page **hvp = &hv_vp_assist_page[smp_processor_id()];
-	void **input_arg;
-	struct page *pg;
-
-	/* hv_cpu_init() can be called with IRQs disabled from hv_resume() */
-	pg = alloc_pages(irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL, hv_root_partition ? 1 : 0);
-	if (unlikely(!pg))
-		return -ENOMEM;
-
-	input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
-	*input_arg = page_address(pg);
-	if (hv_root_partition) {
-		void **output_arg;
-
-		output_arg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
-		*output_arg = page_address(pg + 1);
-	}
-
-	msr_vp_index = hv_get_register(HV_REGISTER_VP_INDEX);
-
-	hv_vp_index[smp_processor_id()] = msr_vp_index;
+	int ret;
 
-	if (msr_vp_index > hv_max_vp_index)
-		hv_max_vp_index = msr_vp_index;
+	ret = hv_common_cpu_init(cpu);
+	if (ret)
+		return ret;
 
 	if (!hv_vp_assist_page)
 		return 0;
@@ -198,25 +167,8 @@ static int hv_cpu_die(unsigned int cpu)
 {
 	struct hv_reenlightenment_control re_ctrl;
 	unsigned int new_cpu;
-	unsigned long flags;
-	void **input_arg;
-	void *pg;
 
-	local_irq_save(flags);
-	input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
-	pg = *input_arg;
-	*input_arg = NULL;
-
-	if (hv_root_partition) {
-		void **output_arg;
-
-		output_arg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
-		*output_arg = NULL;
-	}
-
-	local_irq_restore(flags);
-
-	free_pages((unsigned long)pg, hv_root_partition ? 1 : 0);
+	hv_common_cpu_die(cpu);
 
 	if (hv_vp_assist_page && hv_vp_assist_page[cpu])
 		wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, 0);
@@ -368,7 +320,7 @@ void __init hyperv_init(void)
 {
 	u64 guest_id, required_msrs;
 	union hv_x64_msr_hypercall_contents hypercall_msr;
-	int cpuhp, i;
+	int cpuhp;
 
 	if (x86_hyper_type != X86_HYPER_MS_HYPERV)
 		return;
@@ -380,36 +332,14 @@ void __init hyperv_init(void)
 	if ((ms_hyperv.features & required_msrs) != required_msrs)
 		return;
 
-	/*
-	 * Allocate the per-CPU state for the hypercall input arg.
-	 * If this allocation fails, we will not be able to setup
-	 * (per-CPU) hypercall input page and thus this failure is
-	 * fatal on Hyper-V.
-	 */
-	hyperv_pcpu_input_arg = alloc_percpu(void  *);
-
-	BUG_ON(hyperv_pcpu_input_arg == NULL);
-
-	/* Allocate the per-CPU state for output arg for root */
-	if (hv_root_partition) {
-		hyperv_pcpu_output_arg = alloc_percpu(void *);
-		BUG_ON(hyperv_pcpu_output_arg == NULL);
-	}
-
-	/* Allocate percpu VP index */
-	hv_vp_index = kmalloc_array(num_possible_cpus(), sizeof(*hv_vp_index),
-				    GFP_KERNEL);
-	if (!hv_vp_index)
+	if (hv_common_init())
 		return;
 
-	for (i = 0; i < num_possible_cpus(); i++)
-		hv_vp_index[i] = VP_INVAL;
-
 	hv_vp_assist_page = kcalloc(num_possible_cpus(),
 				    sizeof(*hv_vp_assist_page), GFP_KERNEL);
 	if (!hv_vp_assist_page) {
 		ms_hyperv.hints &= ~HV_X64_ENLIGHTENED_VMCS_RECOMMENDED;
-		goto free_vp_index;
+		goto common_free;
 	}
 
 	cpuhp = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/hyperv_init:online",
@@ -507,9 +437,8 @@ void __init hyperv_init(void)
 free_vp_assist_page:
 	kfree(hv_vp_assist_page);
 	hv_vp_assist_page = NULL;
-free_vp_index:
-	kfree(hv_vp_index);
-	hv_vp_index = NULL;
+common_free:
+	hv_common_free();
 }
 
 /*
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 67ff0d6..adccbc20 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -36,8 +36,6 @@ static inline u64 hv_get_register(unsigned int reg)
 extern int hyperv_init_cpuhp;
 
 extern void *hv_hypercall_pg;
-extern void  __percpu  **hyperv_pcpu_input_arg;
-extern void  __percpu  **hyperv_pcpu_output_arg;
 
 extern u64 hv_current_partition_id;
 
@@ -170,8 +168,6 @@ int hyperv_fill_flush_guest_mapping_list(
 		struct hv_guest_mapping_flush_list *flush,
 		u64 start_gfn, u64 end_gfn);
 
-extern bool hv_root_partition;
-
 #ifdef CONFIG_X86_64
 void hv_apic_init(void);
 void __init hv_init_spinlocks(void);
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index cc8f177..9bcf417 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -34,13 +34,6 @@
 #include <clocksource/hyperv_timer.h>
 #include <asm/numa.h>
 
-/* Is Linux running as the root partition? */
-bool hv_root_partition;
-EXPORT_SYMBOL_GPL(hv_root_partition);
-
-struct ms_hyperv_info ms_hyperv;
-EXPORT_SYMBOL_GPL(ms_hyperv);
-
 #if IS_ENABLED(CONFIG_HYPERV)
 static void (*vmbus_handler)(void);
 static void (*hv_stimer0_handler)(void);
diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index 7f42da9..9305850 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -15,10 +15,141 @@
 #include <linux/types.h>
 #include <linux/export.h>
 #include <linux/bitfield.h>
+#include <linux/cpumask.h>
+#include <linux/slab.h>
 #include <asm/hyperv-tlfs.h>
 #include <asm/mshyperv.h>
 
 
+/* Is Linux running as the root partition? */
+bool hv_root_partition;
+EXPORT_SYMBOL_GPL(hv_root_partition);
+
+struct ms_hyperv_info ms_hyperv;
+EXPORT_SYMBOL_GPL(ms_hyperv);
+
+u32 *hv_vp_index;
+EXPORT_SYMBOL_GPL(hv_vp_index);
+
+u32 hv_max_vp_index;
+EXPORT_SYMBOL_GPL(hv_max_vp_index);
+
+void  __percpu **hyperv_pcpu_input_arg;
+EXPORT_SYMBOL_GPL(hyperv_pcpu_input_arg);
+
+void  __percpu **hyperv_pcpu_output_arg;
+EXPORT_SYMBOL_GPL(hyperv_pcpu_output_arg);
+
+/*
+ * Hyper-V specific initialization and shutdown code that is
+ * common across all architectures.  Called from architecture
+ * specific initialization functions.
+ */
+
+void __init hv_common_free(void)
+{
+	kfree(hv_vp_index);
+	hv_vp_index = NULL;
+
+	free_percpu(hyperv_pcpu_output_arg);
+	hyperv_pcpu_output_arg = NULL;
+
+	free_percpu(hyperv_pcpu_input_arg);
+	hyperv_pcpu_input_arg = NULL;
+}
+
+int __init hv_common_init(void)
+{
+	int i;
+
+	/*
+	 * Allocate the per-CPU state for the hypercall input arg.
+	 * If this allocation fails, we will not be able to setup
+	 * (per-CPU) hypercall input page and thus this failure is
+	 * fatal on Hyper-V.
+	 */
+	hyperv_pcpu_input_arg = alloc_percpu(void  *);
+	BUG_ON(!hyperv_pcpu_input_arg);
+
+	/* Allocate the per-CPU state for output arg for root */
+	if (hv_root_partition) {
+		hyperv_pcpu_output_arg = alloc_percpu(void *);
+		BUG_ON(!hyperv_pcpu_output_arg);
+	}
+
+	hv_vp_index = kmalloc_array(num_possible_cpus(), sizeof(*hv_vp_index),
+				    GFP_KERNEL);
+	if (!hv_vp_index) {
+		hv_common_free();
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < num_possible_cpus(); i++)
+		hv_vp_index[i] = VP_INVAL;
+
+	return 0;
+}
+
+/*
+ * Hyper-V specific initialization and die code for
+ * individual CPUs that is common across all architectures.
+ * Called by the CPU hotplug mechanism.
+ */
+
+int hv_common_cpu_init(unsigned int cpu)
+{
+	void **inputarg, **outputarg;
+	u64 msr_vp_index;
+	gfp_t flags;
+	int pgcount = hv_root_partition ? 2 : 1;
+
+	/* hv_cpu_init() can be called with IRQs disabled from hv_resume() */
+	flags = irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL;
+
+	inputarg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
+	*inputarg = kmalloc(pgcount * HV_HYP_PAGE_SIZE, flags);
+	if (!(*inputarg))
+		return -ENOMEM;
+
+	if (hv_root_partition) {
+		outputarg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
+		*outputarg = (char *)(*inputarg) + HV_HYP_PAGE_SIZE;
+	}
+
+	msr_vp_index = hv_get_register(HV_REGISTER_VP_INDEX);
+
+	hv_vp_index[cpu] = msr_vp_index;
+
+	if (msr_vp_index > hv_max_vp_index)
+		hv_max_vp_index = msr_vp_index;
+
+	return 0;
+}
+
+int hv_common_cpu_die(unsigned int cpu)
+{
+	unsigned long flags;
+	void **inputarg, **outputarg;
+	void *mem;
+
+	local_irq_save(flags);
+
+	inputarg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
+	mem = *inputarg;
+	*inputarg = NULL;
+
+	if (hv_root_partition) {
+		outputarg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
+		*outputarg = NULL;
+	}
+
+	local_irq_restore(flags);
+
+	kfree(mem);
+
+	return 0;
+}
+
 /* Bit mask of the extended capability to query: see HV_EXT_CAPABILITY_xxx */
 bool hv_query_ext_cap(u64 cap_query)
 {
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index 9a000ba..2a187fe 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -38,6 +38,9 @@ struct ms_hyperv_info {
 };
 extern struct ms_hyperv_info ms_hyperv;
 
+extern void  __percpu  **hyperv_pcpu_input_arg;
+extern void  __percpu  **hyperv_pcpu_output_arg;
+
 extern u64 hv_do_hypercall(u64 control, void *inputaddr, void *outputaddr);
 extern u64 hv_do_fast_hypercall8(u16 control, u64 input8);
 
@@ -151,6 +154,8 @@ static inline void vmbus_signal_eom(struct hv_message *msg, u32 old_msg_type)
 extern int vmbus_interrupt;
 extern int vmbus_irq;
 
+extern bool hv_root_partition;
+
 #if IS_ENABLED(CONFIG_HYPERV)
 /*
  * Hypervisor's notion of virtual processor ID is different from
@@ -164,6 +169,11 @@ static inline void vmbus_signal_eom(struct hv_message *msg, u32 old_msg_type)
 /* Sentinel value for an uninitialized entry in hv_vp_index array */
 #define VP_INVAL	U32_MAX
 
+int __init hv_common_init(void);
+void __init hv_common_free(void);
+int hv_common_cpu_init(unsigned int cpu);
+int hv_common_cpu_die(unsigned int cpu);
+
 void *hv_alloc_hyperv_page(void);
 void *hv_alloc_hyperv_zeroed_page(void);
 void hv_free_hyperv_page(unsigned long addr);
-- 
1.8.3.1

Re: [PATCH 1/3] Drivers: hv: Make portions of Hyper-V init code be arch neutral

[Wei Liu]

On Sun, Jul 11, 2021 at 08:25:14PM -0700, Michael Kelley wrote:
[...]
> +int hv_common_cpu_init(unsigned int cpu)
> +{
> +	void **inputarg, **outputarg;
> +	u64 msr_vp_index;
> +	gfp_t flags;
> +	int pgcount = hv_root_partition ? 2 : 1;
> +
> +	/* hv_cpu_init() can be called with IRQs disabled from hv_resume() */
> +	flags = irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL;
> +
> +	inputarg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
> +	*inputarg = kmalloc(pgcount * HV_HYP_PAGE_SIZE, flags);

This is changed from alloc_pages to kmalloc. Does it ensure the
alignment is still correct? 

Wei.

Re: [PATCH 1/3] Drivers: hv: Make portions of Hyper-V init code be arch neutral

[Wei Liu]

On Mon, Jul 12, 2021 at 06:24:00PM +0000, Wei Liu wrote:
> On Sun, Jul 11, 2021 at 08:25:14PM -0700, Michael Kelley wrote:
> [...]
> > +int hv_common_cpu_init(unsigned int cpu)
> > +{
> > +	void **inputarg, **outputarg;
> > +	u64 msr_vp_index;
> > +	gfp_t flags;
> > +	int pgcount = hv_root_partition ? 2 : 1;
> > +
> > +	/* hv_cpu_init() can be called with IRQs disabled from hv_resume() */
> > +	flags = irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL;
> > +
> > +	inputarg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
> > +	*inputarg = kmalloc(pgcount * HV_HYP_PAGE_SIZE, flags);
> 
> This is changed from alloc_pages to kmalloc. Does it ensure the
> alignment is still correct? 

kmalloc is rather complex and can be backed by either SLUB, SLAB or
SLOB, all of which differ from the others.

I _think_ for large allocations (> 1 native page) they tend to pass the
request on to the page allocator, but still there is a level of
indirection.

If the host page size is 64KiB, while the allocation is only 4KiB or
8KiB, could there be a chance that they become misaligned?

Wei.

> 
> Wei.

RE: [PATCH 1/3] Drivers: hv: Make portions of Hyper-V init code be arch neutral

[Michael Kelley]

From: Wei Liu <wei.liu@kernel.org> Sent: Monday, July 12, 2021 11:24 AM
> 
> On Sun, Jul 11, 2021 at 08:25:14PM -0700, Michael Kelley wrote:
> [...]
> > +int hv_common_cpu_init(unsigned int cpu)
> > +{
> > +	void **inputarg, **outputarg;
> > +	u64 msr_vp_index;
> > +	gfp_t flags;
> > +	int pgcount = hv_root_partition ? 2 : 1;
> > +
> > +	/* hv_cpu_init() can be called with IRQs disabled from hv_resume() */
> > +	flags = irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL;
> > +
> > +	inputarg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
> > +	*inputarg = kmalloc(pgcount * HV_HYP_PAGE_SIZE, flags);
> 
> This is changed from alloc_pages to kmalloc. Does it ensure the
> alignment is still correct?
> 
> Wei.

It does.  The alignment guarantee made by kmalloc() was changed a
couple of years ago.  See commit 59bb47985c1d.  Here's the current text
from the comments preceding kmalloc():

* The allocated object address is aligned to at least ARCH_KMALLOC_MINALIGN
 * bytes. For @size of power of two bytes, the alignment is also guaranteed
 * to be at least to the size.

Michael

Re: [PATCH 1/3] Drivers: hv: Make portions of Hyper-V init code be arch neutral

[Wei Liu]

On Mon, Jul 12, 2021 at 06:41:21PM +0000, Michael Kelley wrote:
> From: Wei Liu <wei.liu@kernel.org> Sent: Monday, July 12, 2021 11:24 AM
> > 
> > On Sun, Jul 11, 2021 at 08:25:14PM -0700, Michael Kelley wrote:
> > [...]
> > > +int hv_common_cpu_init(unsigned int cpu)
> > > +{
> > > +	void **inputarg, **outputarg;
> > > +	u64 msr_vp_index;
> > > +	gfp_t flags;
> > > +	int pgcount = hv_root_partition ? 2 : 1;
> > > +
> > > +	/* hv_cpu_init() can be called with IRQs disabled from hv_resume() */
> > > +	flags = irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL;
> > > +
> > > +	inputarg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
> > > +	*inputarg = kmalloc(pgcount * HV_HYP_PAGE_SIZE, flags);
> > 
> > This is changed from alloc_pages to kmalloc. Does it ensure the
> > alignment is still correct?
> > 
> > Wei.
> 
> It does.  The alignment guarantee made by kmalloc() was changed a
> couple of years ago.  See commit 59bb47985c1d.  Here's the current text
> from the comments preceding kmalloc():
> 
> * The allocated object address is aligned to at least ARCH_KMALLOC_MINALIGN
>  * bytes. For @size of power of two bytes, the alignment is also guaranteed
>  * to be at least to the size.

OK. That's good.

Wei.

> 
> Michael
> 

[PATCH 2/3] Drivers: hv: Add arch independent default functions for some Hyper-V handlers

[Michael Kelley]

Architecture independent Hyper-V code calls various arch-specific handlers
when needed.  To aid in supporting multiple architectures, provide weak
defaults that can be overridden by arch-specific implementations where
appropriate.  But when arch-specific overrides aren't needed or haven't
been implemented yet for a particular architecture, these stubs reduce
the amount of clutter under arch/.

No functional change.

Signed-off-by: Michael Kelley <mikelley@microsoft.com>
---
 arch/x86/hyperv/hv_init.c      |  2 --
 arch/x86/kernel/cpu/mshyperv.c |  6 ------
 drivers/hv/hv_common.c         | 49 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 49 insertions(+), 8 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 5cc0c0f..e87a029 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -468,7 +468,6 @@ void hyperv_cleanup(void)
 	hypercall_msr.as_uint64 = 0;
 	wrmsrl(HV_X64_MSR_REFERENCE_TSC, hypercall_msr.as_uint64);
 }
-EXPORT_SYMBOL_GPL(hyperv_cleanup);
 
 void hyperv_report_panic(struct pt_regs *regs, long err, bool in_die)
 {
@@ -542,4 +541,3 @@ bool hv_is_isolation_supported(void)
 {
 	return hv_get_isolation_type() != HV_ISOLATION_TYPE_NONE;
 }
-EXPORT_SYMBOL_GPL(hv_is_isolation_supported);
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 9bcf417..3e5a3f5 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -58,14 +58,12 @@ void hv_setup_vmbus_handler(void (*handler)(void))
 {
 	vmbus_handler = handler;
 }
-EXPORT_SYMBOL_GPL(hv_setup_vmbus_handler);
 
 void hv_remove_vmbus_handler(void)
 {
 	/* We have no way to deallocate the interrupt gate */
 	vmbus_handler = NULL;
 }
-EXPORT_SYMBOL_GPL(hv_remove_vmbus_handler);
 
 /*
  * Routines to do per-architecture handling of stimer0
@@ -100,25 +98,21 @@ void hv_setup_kexec_handler(void (*handler)(void))
 {
 	hv_kexec_handler = handler;
 }
-EXPORT_SYMBOL_GPL(hv_setup_kexec_handler);
 
 void hv_remove_kexec_handler(void)
 {
 	hv_kexec_handler = NULL;
 }
-EXPORT_SYMBOL_GPL(hv_remove_kexec_handler);
 
 void hv_setup_crash_handler(void (*handler)(struct pt_regs *regs))
 {
 	hv_crash_handler = handler;
 }
-EXPORT_SYMBOL_GPL(hv_setup_crash_handler);
 
 void hv_remove_crash_handler(void)
 {
 	hv_crash_handler = NULL;
 }
-EXPORT_SYMBOL_GPL(hv_remove_crash_handler);
 
 #ifdef CONFIG_KEXEC_CORE
 static void hv_machine_shutdown(void)
diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index 9305850..c429306 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -16,6 +16,7 @@
 #include <linux/export.h>
 #include <linux/bitfield.h>
 #include <linux/cpumask.h>
+#include <linux/ptrace.h>
 #include <linux/slab.h>
 #include <asm/hyperv-tlfs.h>
 #include <asm/mshyperv.h>
@@ -195,3 +196,51 @@ bool hv_query_ext_cap(u64 cap_query)
 	return hv_extended_cap & cap_query;
 }
 EXPORT_SYMBOL_GPL(hv_query_ext_cap);
+
+/* These __weak functions provide default "no-op" behavior and
+ * may be overridden by architecture specific versions. Architectures
+ * for which the default "no-op" behavior is sufficient can leave
+ * them unimplemented and not be cluttered with a bunch of stub
+ * functions in arch-specific code.
+ */
+
+bool __weak hv_is_isolation_supported(void)
+{
+	return false;
+}
+EXPORT_SYMBOL_GPL(hv_is_isolation_supported);
+
+void __weak hv_setup_vmbus_handler(void (*handler)(void))
+{
+}
+EXPORT_SYMBOL_GPL(hv_setup_vmbus_handler);
+
+void __weak hv_remove_vmbus_handler(void)
+{
+}
+EXPORT_SYMBOL_GPL(hv_remove_vmbus_handler);
+
+void __weak hv_setup_kexec_handler(void (*handler)(void))
+{
+}
+EXPORT_SYMBOL_GPL(hv_setup_kexec_handler);
+
+void __weak hv_remove_kexec_handler(void)
+{
+}
+EXPORT_SYMBOL_GPL(hv_remove_kexec_handler);
+
+void __weak hv_setup_crash_handler(void (*handler)(struct pt_regs *regs))
+{
+}
+EXPORT_SYMBOL_GPL(hv_setup_crash_handler);
+
+void __weak hv_remove_crash_handler(void)
+{
+}
+EXPORT_SYMBOL_GPL(hv_remove_crash_handler);
+
+void __weak hyperv_cleanup(void)
+{
+}
+EXPORT_SYMBOL_GPL(hyperv_cleanup);
-- 
1.8.3.1

[PATCH 3/3] Drivers: hv: Move Hyper-V misc functionality to arch-neutral code

[Michael Kelley]

The check for whether hibernation is possible, and the enabling of
Hyper-V panic notification during kexec, are both architecture neutral.
Move the code from under arch/x86 and into drivers/hv/hv_common.c where
it can also be used for ARM64.

No functional change.

Signed-off-by: Michael Kelley <mikelley@microsoft.com>
---
 arch/x86/hyperv/hv_init.c      |  8 +-------
 arch/x86/kernel/cpu/mshyperv.c | 11 -----------
 drivers/hv/hv_common.c         | 18 ++++++++++++++++++
 3 files changed, 19 insertions(+), 18 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index e87a029..6f247e7 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -7,10 +7,10 @@
  * Author : K. Y. Srinivasan <kys@microsoft.com>
  */
 
-#include <linux/acpi.h>
 #include <linux/efi.h>
 #include <linux/types.h>
 #include <linux/bitfield.h>
+#include <linux/io.h>
 #include <asm/apic.h>
 #include <asm/desc.h>
 #include <asm/hypervisor.h>
@@ -523,12 +523,6 @@ bool hv_is_hyperv_initialized(void)
 }
 EXPORT_SYMBOL_GPL(hv_is_hyperv_initialized);
 
-bool hv_is_hibernation_supported(void)
-{
-	return !hv_root_partition && acpi_sleep_state_supported(ACPI_STATE_S4);
-}
-EXPORT_SYMBOL_GPL(hv_is_hibernation_supported);
-
 enum hv_isolation_type hv_get_isolation_type(void)
 {
 	if (!(ms_hyperv.priv_high & HV_ISOLATION))
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 3e5a3f5..ec428e2 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -17,7 +17,6 @@
 #include <linux/irq.h>
 #include <linux/kexec.h>
 #include <linux/i8253.h>
-#include <linux/panic_notifier.h>
 #include <linux/random.h>
 #include <asm/processor.h>
 #include <asm/hypervisor.h>
@@ -322,16 +321,6 @@ static void __init ms_hyperv_init_platform(void)
 			ms_hyperv.nested_features);
 	}
 
-	/*
-	 * Hyper-V expects to get crash register data or kmsg when
-	 * crash enlightment is available and system crashes. Set
-	 * crash_kexec_post_notifiers to be true to make sure that
-	 * calling crash enlightment interface before running kdump
-	 * kernel.
-	 */
-	if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE)
-		crash_kexec_post_notifiers = true;
-
 #ifdef CONFIG_X86_LOCAL_APIC
 	if (ms_hyperv.features & HV_ACCESS_FREQUENCY_MSRS &&
 	    ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE) {
diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index c429306..3ff8446 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -13,9 +13,11 @@
  */
 
 #include <linux/types.h>
+#include <linux/acpi.h>
 #include <linux/export.h>
 #include <linux/bitfield.h>
 #include <linux/cpumask.h>
+#include <linux/panic_notifier.h>
 #include <linux/ptrace.h>
 #include <linux/slab.h>
 #include <asm/hyperv-tlfs.h>
@@ -64,6 +66,16 @@ int __init hv_common_init(void)
 	int i;
 
 	/*
+	 * Hyper-V expects to get crash register data or kmsg when
+	 * crash enlightment is available and system crashes. Set
+	 * crash_kexec_post_notifiers to be true to make sure that
+	 * calling crash enlightment interface before running kdump
+	 * kernel.
+	 */
+	if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE)
+		crash_kexec_post_notifiers = true;
+
+	/*
 	 * Allocate the per-CPU state for the hypercall input arg.
 	 * If this allocation fails, we will not be able to setup
 	 * (per-CPU) hypercall input page and thus this failure is
@@ -197,6 +209,12 @@ bool hv_query_ext_cap(u64 cap_query)
 }
 EXPORT_SYMBOL_GPL(hv_query_ext_cap);
 
+bool hv_is_hibernation_supported(void)
+{
+	return !hv_root_partition && acpi_sleep_state_supported(ACPI_STATE_S4);
+}
+EXPORT_SYMBOL_GPL(hv_is_hibernation_supported);
+
 /* These __weak functions provide default "no-op" behavior and
  * may be overridden by architecture specific versions. Architectures
  * for which the default "no-op" behavior is sufficient can leave
-- 
1.8.3.1

Re: [PATCH 0/3] Additional refactoring of Hyper-V arch specific code

[Wei Liu]

On Sun, Jul 11, 2021 at 08:25:13PM -0700, Michael Kelley wrote:
> This patch set moves additional Hyper-V code under arch/x86 into
> arch-neutral hv_common.c where it can be shared by x86 and
> and ARM64 implementations.  The move reduces the overall lines
> of code across both architectures, and removes code under
> arch/ that isn't really architecture-specific.
> 
> The code is moved into hv_common.c because it must be
> built-in to the kernel image, and not be part of a module.
> 
> No functional changes are intended.
> Michael Kelley (3):
>   Drivers: hv: Make portions of Hyper-V init code be arch neutral
>   Drivers: hv: Add arch independent default functions for some Hyper-V
>     handlers
>   Drivers: hv: Move Hyper-V misc functionality to arch-neutral code
> 
>  arch/x86/hyperv/hv_init.c       | 101 +++-----------------
>  arch/x86/include/asm/mshyperv.h |   4 -
>  arch/x86/kernel/cpu/mshyperv.c  |  24 -----
>  drivers/hv/hv_common.c          | 198 ++++++++++++++++++++++++++++++++++++++++
>  include/asm-generic/mshyperv.h  |  10 ++
>  5 files changed, 219 insertions(+), 118 deletions(-)
> 

Applied to hyperv-next. Thanks.

> -- 
> 1.8.3.1
>