Commit 461fbbd0 authored by Nuno Das Neves's avatar Nuno Das Neves Committed by Wei Liu
Browse files

hyperv: Add CONFIG_MSHV_ROOT to gate root partition support 



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: default avatarNuno Das Neves <nunodasneves@linux.microsoft.com>
Reviewed-by: default avatarEaswar Hariharan <eahariha@linux.microsoft.com>
Reviewed-by: default avatarMichael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/1740167795-13296-4-git-send-email-nunodasneves@linux.microsoft.com


Signed-off-by: default avatarWei Liu <wei.liu@kernel.org>
Message-ID: <1740167795-13296-4-git-send-email-nunodasneves@linux.microsoft.com>
parent db912b89

drivers/hv/Kconfig

+16 −0
Original line number Diff line number Diff line
@@ -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 && (X86_64 || ARM64)

	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

drivers/hv/Makefile

+2 −1
Original line number Diff line number Diff line
@@ -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

drivers/hv/hv_common.c

+4 −1
Original line number Diff line number Diff line
@@ -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");

		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");

	}

}

include/asm-generic/mshyperv.h

+20 −4
Original line number Diff line number Diff line
@@ -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