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.
Signed-off-by: Nuno Das Neves <nunodasneves@xxxxxxxxxxxxxxxxxxx>
---
drivers/hv/Kconfig | 16 ++++++++++++++++
drivers/hv/Makefile | 3 ++-
include/asm-generic/mshyperv.h | 24 ++++++++++++++++++++----
3 files changed, 38 insertions(+), 5 deletions(-)
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/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index d2b1a8fc074c..b29357cff2f7 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_current_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
