diff mbox series

[v3,3/3] hyperv: Add CONFIG_MSHV_ROOT to gate root partition support

Message ID 1740167795-13296-4-git-send-email-nunodasneves@linux.microsoft.com (mailing list archive)
State New
Headers show
Series Introduce CONFIG_MSHV_ROOT for root partition code | expand

Commit Message

Nuno Das Neves Feb. 21, 2025, 7:56 p.m. UTC 
CONFIG_MSHV_ROOT allows kernels built to run as a normal Hyper-V guest
to exclude the root partition code, which is expected to grow
significantly over time.

This option is a tristate so future driver code can be built as a
(m)odule, allowing faster development iteration cycles.

If CONFIG_MSHV_ROOT is disabled, don't compile hv_proc.c, and stub
hv_root_partition() to return false unconditionally. This allows the
compiler to optimize away root partition code blocks since they will
be disabled at compile time.

In the case of booting as root partition *without* CONFIG_MSHV_ROOT
enabled, print a critical error (the kernel will likely crash).

Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Reviewed-by: Easwar Hariharan <eahariha@linux.microsoft.com>
---
 drivers/hv/Kconfig             | 16 ++++++++++++++++
 drivers/hv/Makefile            |  3 ++-
 drivers/hv/hv_common.c         |  5 ++++-
 include/asm-generic/mshyperv.h | 24 ++++++++++++++++++++----
 4 files changed, 42 insertions(+), 6 deletions(-)

Comments

Michael Kelley Feb. 21, 2025, 8:59 p.m. UTC | #1 
From: Nuno Das Neves <nunodasneves@linux.microsoft.com> Sent: Friday, February 21, 2025 11:57 AM
> 
> CONFIG_MSHV_ROOT allows kernels built to run as a normal Hyper-V guest
> to exclude the root partition code, which is expected to grow
> significantly over time.
> 
> This option is a tristate so future driver code can be built as a
> (m)odule, allowing faster development iteration cycles.
> 
> If CONFIG_MSHV_ROOT is disabled, don't compile hv_proc.c, and stub
> hv_root_partition() to return false unconditionally. This allows the
> compiler to optimize away root partition code blocks since they will
> be disabled at compile time.
> 
> In the case of booting as root partition *without* CONFIG_MSHV_ROOT
> enabled, print a critical error (the kernel will likely crash).
> 
> Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
> Reviewed-by: Easwar Hariharan <eahariha@linux.microsoft.com>
> ---
>  drivers/hv/Kconfig             | 16 ++++++++++++++++
>  drivers/hv/Makefile            |  3 ++-
>  drivers/hv/hv_common.c         |  5 ++++-
>  include/asm-generic/mshyperv.h | 24 ++++++++++++++++++++----
>  4 files changed, 42 insertions(+), 6 deletions(-)

Reviewed-by: Michael Kelley <mhklinux@outlook.com>

> 
> diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
> index 862c47b191af..794e88e9dc6b 100644
> --- a/drivers/hv/Kconfig
> +++ b/drivers/hv/Kconfig
> @@ -55,4 +55,20 @@ config HYPERV_BALLOON
>  	help
>  	  Select this option to enable Hyper-V Balloon driver.
> 
> +config MSHV_ROOT
> +	tristate "Microsoft Hyper-V root partition support"
> +	depends on HYPERV
> +	depends on !HYPERV_VTL_MODE
> +	# The hypervisor interface operates on 4k pages. Enforcing it here
> +	# simplifies many assumptions in the root partition code.
> +	# e.g. When withdrawing memory, the hypervisor gives back 4k pages in
> +	# no particular order, making it impossible to reassemble larger pages
> +	depends on PAGE_SIZE_4KB
> +	default n
> +	help
> +	  Select this option to enable support for booting and running as root
> +	  partition on Microsoft Hyper-V.
> +
> +	  If unsure, say N.
> +
>  endmenu
> diff --git a/drivers/hv/Makefile b/drivers/hv/Makefile
> index 9afcabb3fbd2..2b8dc954b350 100644
> --- a/drivers/hv/Makefile
> +++ b/drivers/hv/Makefile
> @@ -13,4 +13,5 @@ hv_vmbus-$(CONFIG_HYPERV_TESTING)	+= hv_debugfs.o
>  hv_utils-y := hv_util.o hv_kvp.o hv_snapshot.o hv_utils_transport.o
> 
>  # Code that must be built-in
> -obj-$(subst m,y,$(CONFIG_HYPERV)) += hv_common.o hv_proc.o
> +obj-$(subst m,y,$(CONFIG_HYPERV)) += hv_common.o
> +obj-$(subst m,y,$(CONFIG_MSHV_ROOT)) += hv_proc.o
> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> index 3d9cfcfbc854..9804adb4cc56 100644
> --- a/drivers/hv/hv_common.c
> +++ b/drivers/hv/hv_common.c
> @@ -734,6 +734,9 @@ void hv_identify_partition_type(void)
>  	    (ms_hyperv.priv_high & HV_CPU_MANAGEMENT) &&
>  	    !(ms_hyperv.priv_high & HV_ISOLATION)) {
>  		pr_info("Hyper-V: running as root partition\n");
> -		hv_curr_partition_type = HV_PARTITION_TYPE_ROOT;
> +		if (IS_ENABLED(CONFIG_MSHV_ROOT))
> +			hv_curr_partition_type = HV_PARTITION_TYPE_ROOT;
> +		else
> +			pr_crit("Hyper-V: CONFIG_MSHV_ROOT not enabled!\n");
>  	}
>  }
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index 54ebd630e72c..b13b0cda4ac8 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -223,10 +223,6 @@ void *hv_alloc_hyperv_page(void);
>  void *hv_alloc_hyperv_zeroed_page(void);
>  void hv_free_hyperv_page(void *addr);
> 
> -int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages);
> -int hv_call_add_logical_proc(int node, u32 lp_index, u32 acpi_id);
> -int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u32 flags);
> -
>  /**
>   * hv_cpu_number_to_vp_number() - Map CPU to VP.
>   * @cpu_number: CPU number in Linux terms
> @@ -327,9 +323,29 @@ static inline enum hv_isolation_type
> hv_get_isolation_type(void)
>  }
>  #endif /* CONFIG_HYPERV */
> 
> +#if IS_ENABLED(CONFIG_MSHV_ROOT)
>  static inline bool hv_root_partition(void)
>  {
>  	return hv_curr_partition_type == HV_PARTITION_TYPE_ROOT;
>  }
> +int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages);
> +int hv_call_add_logical_proc(int node, u32 lp_index, u32 acpi_id);
> +int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u32 flags);
> +
> +#else /* CONFIG_MSHV_ROOT */
> +static inline bool hv_root_partition(void) { return false; }
> +static inline int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages)
> +{
> +	return -EOPNOTSUPP;
> +}
> +static inline int hv_call_add_logical_proc(int node, u32 lp_index, u32 acpi_id)
> +{
> +	return -EOPNOTSUPP;
> +}
> +static inline int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u32 flags)
> +{
> +	return -EOPNOTSUPP;
> +}
> +#endif /* CONFIG_MSHV_ROOT */
> 
>  #endif
> --
> 2.34.1
diff mbox series

Patch

diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
index 862c47b191af..794e88e9dc6b 100644
--- a/drivers/hv/Kconfig
+++ b/drivers/hv/Kconfig
@@ -55,4 +55,20 @@  config HYPERV_BALLOON
 	help
 	  Select this option to enable Hyper-V Balloon driver.
 
+config MSHV_ROOT
+	tristate "Microsoft Hyper-V root partition support"
+	depends on HYPERV
+	depends on !HYPERV_VTL_MODE
+	# The hypervisor interface operates on 4k pages. Enforcing it here
+	# simplifies many assumptions in the root partition code.
+	# e.g. When withdrawing memory, the hypervisor gives back 4k pages in
+	# no particular order, making it impossible to reassemble larger pages
+	depends on PAGE_SIZE_4KB
+	default n
+	help
+	  Select this option to enable support for booting and running as root
+	  partition on Microsoft Hyper-V.
+
+	  If unsure, say N.
+
 endmenu
diff --git a/drivers/hv/Makefile b/drivers/hv/Makefile
index 9afcabb3fbd2..2b8dc954b350 100644
--- a/drivers/hv/Makefile
+++ b/drivers/hv/Makefile
@@ -13,4 +13,5 @@  hv_vmbus-$(CONFIG_HYPERV_TESTING)	+= hv_debugfs.o
 hv_utils-y := hv_util.o hv_kvp.o hv_snapshot.o hv_utils_transport.o
 
 # Code that must be built-in
-obj-$(subst m,y,$(CONFIG_HYPERV)) += hv_common.o hv_proc.o
+obj-$(subst m,y,$(CONFIG_HYPERV)) += hv_common.o
+obj-$(subst m,y,$(CONFIG_MSHV_ROOT)) += hv_proc.o
diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index 3d9cfcfbc854..9804adb4cc56 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -734,6 +734,9 @@  void hv_identify_partition_type(void)
 	    (ms_hyperv.priv_high & HV_CPU_MANAGEMENT) &&
 	    !(ms_hyperv.priv_high & HV_ISOLATION)) {
 		pr_info("Hyper-V: running as root partition\n");
-		hv_curr_partition_type = HV_PARTITION_TYPE_ROOT;
+		if (IS_ENABLED(CONFIG_MSHV_ROOT))
+			hv_curr_partition_type = HV_PARTITION_TYPE_ROOT;
+		else
+			pr_crit("Hyper-V: CONFIG_MSHV_ROOT not enabled!\n");
 	}
 }
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index 54ebd630e72c..b13b0cda4ac8 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -223,10 +223,6 @@  void *hv_alloc_hyperv_page(void);
 void *hv_alloc_hyperv_zeroed_page(void);
 void hv_free_hyperv_page(void *addr);
 
-int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages);
-int hv_call_add_logical_proc(int node, u32 lp_index, u32 acpi_id);
-int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u32 flags);
-
 /**
  * hv_cpu_number_to_vp_number() - Map CPU to VP.
  * @cpu_number: CPU number in Linux terms
@@ -327,9 +323,29 @@  static inline enum hv_isolation_type hv_get_isolation_type(void)
 }
 #endif /* CONFIG_HYPERV */
 
+#if IS_ENABLED(CONFIG_MSHV_ROOT)
 static inline bool hv_root_partition(void)
 {
 	return hv_curr_partition_type == HV_PARTITION_TYPE_ROOT;
 }
+int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages);
+int hv_call_add_logical_proc(int node, u32 lp_index, u32 acpi_id);
+int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u32 flags);
+
+#else /* CONFIG_MSHV_ROOT */
+static inline bool hv_root_partition(void) { return false; }
+static inline int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages)
+{
+	return -EOPNOTSUPP;
+}
+static inline int hv_call_add_logical_proc(int node, u32 lp_index, u32 acpi_id)
+{
+	return -EOPNOTSUPP;
+}
+static inline int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u32 flags)
+{
+	return -EOPNOTSUPP;
+}
+#endif /* CONFIG_MSHV_ROOT */
 
 #endif