Re: [Resend RFC PATCH V2 04/12] HV: Add Write/Read MSR registers via ghcb

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Wed, Apr 14, 2021 at 10:49:37AM -0400, Tianyu Lan wrote:
> From: Tianyu Lan <Tianyu.Lan@microsoft.com>
> 
> Hyper-V provides GHCB protocol to write Synthetic Interrupt
> Controller MSR registers and these registers are emulated by
> Hypervisor rather than paravisor.

What is paravisor? Is that the VMPL0 to borrow AMD speak from
https://www.amd.com/system/files/TechDocs/SEV-SNP-strengthening-vm-isolation-with-integrity-protection-and-more.pdf
 
> 
> Hyper-V requests to write SINTx MSR registers twice(once via
> GHCB and once via wrmsr instruction including the proxy bit 21)

Why? And what does 'proxy bit 21' mean? Isn't it just setting a bit
on the MSR?

Oh. Are you writting to it twice because you need to let the hypervisor
know (Hyper-V) which is done via the WRMSR. And then the inner
hypervisor (VMPL0) via the SINITx MSR?


> Guest OS ID MSR also needs to be set via GHCB.
> 
> Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
> ---
>  arch/x86/hyperv/hv_init.c       |  18 +----
>  arch/x86/hyperv/ivm.c           | 130 ++++++++++++++++++++++++++++++++
>  arch/x86/include/asm/mshyperv.h |  87 +++++++++++++++++----
>  arch/x86/kernel/cpu/mshyperv.c  |   3 +
>  drivers/hv/hv.c                 |  65 +++++++++++-----
>  include/asm-generic/mshyperv.h  |   4 +-
>  6 files changed, 261 insertions(+), 46 deletions(-)
> 
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 90e65fbf4c58..87b1dd9c84d6 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -475,6 +475,9 @@ void __init hyperv_init(void)
>  
>  		ghcb_base = (void **)this_cpu_ptr(ms_hyperv.ghcb_base);
>  		*ghcb_base = ghcb_va;
> +
> +		/* Hyper-V requires to write guest os id via ghcb in SNP IVM. */
> +		hv_ghcb_msr_write(HV_X64_MSR_GUEST_OS_ID, guest_id);
>  	}
>  
>  	rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> @@ -561,6 +564,7 @@ void hyperv_cleanup(void)
>  
>  	/* Reset our OS id */
>  	wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
> +	hv_ghcb_msr_write(HV_X64_MSR_GUEST_OS_ID, 0);
>  
>  	/*
>  	 * Reset hypercall page reference before reset the page,
> @@ -668,17 +672,3 @@ 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.features_b & HV_ISOLATION))
> -		return HV_ISOLATION_TYPE_NONE;
> -	return FIELD_GET(HV_ISOLATION_TYPE, ms_hyperv.isolation_config_b);
> -}
> -EXPORT_SYMBOL_GPL(hv_get_isolation_type);
> -
> -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/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
> index a5950b7a9214..2ec64b367aaf 100644
> --- a/arch/x86/hyperv/ivm.c
> +++ b/arch/x86/hyperv/ivm.c
> @@ -6,12 +6,139 @@
>   *  Tianyu Lan <Tianyu.Lan@microsoft.com>
>   */
>  
> +#include <linux/types.h>
> +#include <linux/bitfield.h>
>  #include <linux/hyperv.h>
>  #include <linux/types.h>
>  #include <linux/bitfield.h>
>  #include <asm/io.h>
> +#include <asm/svm.h>
> +#include <asm/sev-es.h>
>  #include <asm/mshyperv.h>
>  
> +union hv_ghcb {
> +	struct ghcb ghcb;
> +} __packed __aligned(PAGE_SIZE);
> +
> +void hv_ghcb_msr_write(u64 msr, u64 value)
> +{
> +	union hv_ghcb *hv_ghcb;
> +	void **ghcb_base;
> +	unsigned long flags;
> +
> +	if (!ms_hyperv.ghcb_base)
> +		return;
> +
> +	local_irq_save(flags);
> +	ghcb_base = (void **)this_cpu_ptr(ms_hyperv.ghcb_base);
> +	hv_ghcb = (union hv_ghcb *)*ghcb_base;
> +	if (!hv_ghcb) {
> +		local_irq_restore(flags);
> +		return;
> +	}
> +
> +	memset(hv_ghcb, 0x00, HV_HYP_PAGE_SIZE);
> +
> +	hv_ghcb->ghcb.protocol_version = 1;
> +	hv_ghcb->ghcb.ghcb_usage = 0;
> +
> +	ghcb_set_sw_exit_code(&hv_ghcb->ghcb, SVM_EXIT_MSR);
> +	ghcb_set_rcx(&hv_ghcb->ghcb, msr);
> +	ghcb_set_rax(&hv_ghcb->ghcb, lower_32_bits(value));
> +	ghcb_set_rdx(&hv_ghcb->ghcb, value >> 32);
> +	ghcb_set_sw_exit_info_1(&hv_ghcb->ghcb, 1);
> +	ghcb_set_sw_exit_info_2(&hv_ghcb->ghcb, 0);
> +
> +	VMGEXIT();
> +
> +	if ((hv_ghcb->ghcb.save.sw_exit_info_1 & 0xffffffff) == 1)
> +		pr_warn("Fail to write msr via ghcb.\n.");
> +
> +	local_irq_restore(flags);
> +}
> +EXPORT_SYMBOL_GPL(hv_ghcb_msr_write);
> +
> +void hv_ghcb_msr_read(u64 msr, u64 *value)
> +{
> +	union hv_ghcb *hv_ghcb;
> +	void **ghcb_base;
> +	unsigned long flags;
> +
> +	if (!ms_hyperv.ghcb_base)
> +		return;
> +
> +	local_irq_save(flags);
> +	ghcb_base = (void **)this_cpu_ptr(ms_hyperv.ghcb_base);
> +	hv_ghcb = (union hv_ghcb *)*ghcb_base;
> +	if (!hv_ghcb) {
> +		local_irq_restore(flags);
> +		return;
> +	}
> +
> +	memset(hv_ghcb, 0x00, PAGE_SIZE);
> +	hv_ghcb->ghcb.protocol_version = 1;
> +	hv_ghcb->ghcb.ghcb_usage = 0;
> +
> +	ghcb_set_sw_exit_code(&hv_ghcb->ghcb, SVM_EXIT_MSR);
> +	ghcb_set_rcx(&hv_ghcb->ghcb, msr);
> +	ghcb_set_sw_exit_info_1(&hv_ghcb->ghcb, 0);
> +	ghcb_set_sw_exit_info_2(&hv_ghcb->ghcb, 0);
> +
> +	VMGEXIT();
> +
> +	if ((hv_ghcb->ghcb.save.sw_exit_info_1 & 0xffffffff) == 1)
> +		pr_warn("Fail to write msr via ghcb.\n.");
> +	else
> +		*value = (u64)lower_32_bits(hv_ghcb->ghcb.save.rax)
> +			| ((u64)lower_32_bits(hv_ghcb->ghcb.save.rdx) << 32);
> +	local_irq_restore(flags);
> +}
> +EXPORT_SYMBOL_GPL(hv_ghcb_msr_read);
> +
> +void hv_sint_rdmsrl_ghcb(u64 msr, u64 *value)
> +{
> +	hv_ghcb_msr_read(msr, value);
> +}
> +EXPORT_SYMBOL_GPL(hv_sint_rdmsrl_ghcb);
> +
> +void hv_sint_wrmsrl_ghcb(u64 msr, u64 value)
> +{
> +	hv_ghcb_msr_write(msr, value);
> +
> +	/* Write proxy bit vua wrmsrl instruction. */
> +	if (msr >= HV_X64_MSR_SINT0 && msr <= HV_X64_MSR_SINT15)
> +		wrmsrl(msr, value | 1 << 20);
> +}
> +EXPORT_SYMBOL_GPL(hv_sint_wrmsrl_ghcb);
> +
> +inline void hv_signal_eom_ghcb(void)
> +{
> +	hv_sint_wrmsrl_ghcb(HV_X64_MSR_EOM, 0);
> +}
> +EXPORT_SYMBOL_GPL(hv_signal_eom_ghcb);
> +
> +enum hv_isolation_type hv_get_isolation_type(void)
> +{
> +	if (!(ms_hyperv.features_b & HV_ISOLATION))
> +		return HV_ISOLATION_TYPE_NONE;
> +	return FIELD_GET(HV_ISOLATION_TYPE, ms_hyperv.isolation_config_b);
> +}
> +EXPORT_SYMBOL_GPL(hv_get_isolation_type);
> +
> +bool hv_is_isolation_supported(void)
> +{
> +	return hv_get_isolation_type() != HV_ISOLATION_TYPE_NONE;
> +}
> +EXPORT_SYMBOL_GPL(hv_is_isolation_supported);
> +
> +DEFINE_STATIC_KEY_FALSE(isolation_type_snp);
> +
> +bool hv_isolation_type_snp(void)
> +{
> +	return static_branch_unlikely(&isolation_type_snp);
> +}
> +EXPORT_SYMBOL_GPL(hv_isolation_type_snp);
> +
>  /*
>   * hv_set_mem_host_visibility - Set host visibility for specified memory.
>   */
> @@ -22,6 +149,9 @@ int hv_set_mem_host_visibility(void *kbuffer, u32 size, u32 visibility)
>  	u64 *pfn_array;
>  	int ret = 0;
>  
> +	if (!hv_is_isolation_supported())
> +		return 0;
> +
>  	pfn_array = vzalloc(HV_HYP_PAGE_SIZE);
>  	if (!pfn_array)
>  		return -ENOMEM;
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index d9437f096ce5..73501dbbc240 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -10,6 +10,8 @@
>  #include <asm/nospec-branch.h>
>  #include <asm/paravirt.h>
>  
> +DECLARE_STATIC_KEY_FALSE(isolation_type_snp);
> +
>  typedef int (*hyperv_fill_flush_list_func)(
>  		struct hv_guest_mapping_flush_list *flush,
>  		void *data);
> @@ -19,24 +21,64 @@ typedef int (*hyperv_fill_flush_list_func)(
>  #define hv_init_timer_config(timer, val) \
>  	wrmsrl(HV_X64_MSR_STIMER0_CONFIG + (2*timer), val)
>  
> -#define hv_get_simp(val) rdmsrl(HV_X64_MSR_SIMP, val)
> -#define hv_set_simp(val) wrmsrl(HV_X64_MSR_SIMP, val)
> +#define hv_get_sint_reg(val, reg) {		\
> +	if (hv_isolation_type_snp())		\
> +		hv_get_##reg##_ghcb(&val);		\
> +	else					\
> +		rdmsrl(HV_X64_MSR_##reg, val);	\
> +	}
> +
> +#define hv_set_sint_reg(val, reg) {		\
> +	if (hv_isolation_type_snp())		\
> +		hv_set_##reg##_ghcb(val);		\
> +	else					\
> +		wrmsrl(HV_X64_MSR_##reg, val);	\
> +	}
> +
>  
> -#define hv_get_siefp(val) rdmsrl(HV_X64_MSR_SIEFP, val)
> -#define hv_set_siefp(val) wrmsrl(HV_X64_MSR_SIEFP, val)
> +#define hv_get_simp(val) hv_get_sint_reg(val, SIMP)
> +#define hv_get_siefp(val) hv_get_sint_reg(val, SIEFP)
>  
> -#define hv_get_synic_state(val) rdmsrl(HV_X64_MSR_SCONTROL, val)
> -#define hv_set_synic_state(val) wrmsrl(HV_X64_MSR_SCONTROL, val)
> +#define hv_set_simp(val) hv_set_sint_reg(val, SIMP)
> +#define hv_set_siefp(val) hv_set_sint_reg(val, SIEFP)
> +
> +#define hv_get_synic_state(val) {			\
> +	if (hv_isolation_type_snp())			\
> +		hv_get_synic_state_ghcb(&val);		\
> +	else						\
> +		rdmsrl(HV_X64_MSR_SCONTROL, val);	\
> +	}
> +#define hv_set_synic_state(val) {			\
> +	if (hv_isolation_type_snp())			\
> +		hv_set_synic_state_ghcb(val);		\
> +	else						\
> +		wrmsrl(HV_X64_MSR_SCONTROL, val);	\
> +	}
>  
>  #define hv_get_vp_index(index) rdmsrl(HV_X64_MSR_VP_INDEX, index)
>  
> -#define hv_signal_eom() wrmsrl(HV_X64_MSR_EOM, 0)
> +#define hv_signal_eom() {			 \
> +	if (hv_isolation_type_snp() &&		 \
> +	    old_msg_type != HVMSG_TIMER_EXPIRED) \
> +		hv_signal_eom_ghcb();		 \
> +	else					 \
> +		wrmsrl(HV_X64_MSR_EOM, 0);	 \
> +	}
>  
> -#define hv_get_synint_state(int_num, val) \
> -	rdmsrl(HV_X64_MSR_SINT0 + int_num, val)
> -#define hv_set_synint_state(int_num, val) \
> -	wrmsrl(HV_X64_MSR_SINT0 + int_num, val)
> -#define hv_recommend_using_aeoi() \
> +#define hv_get_synint_state(int_num, val) {		\
> +	if (hv_isolation_type_snp())			\
> +		hv_get_synint_state_ghcb(int_num, &val);\
> +	else						\
> +		rdmsrl(HV_X64_MSR_SINT0 + int_num, val);\
> +	}
> +#define hv_set_synint_state(int_num, val) {		\
> +	if (hv_isolation_type_snp())			\
> +		hv_set_synint_state_ghcb(int_num, val);	\
> +	else						\
> +		wrmsrl(HV_X64_MSR_SINT0 + int_num, val);\
> +	}
> +
> +#define hv_recommend_using_aeoi()				\
>  	(!(ms_hyperv.hints & HV_DEPRECATING_AEOI_RECOMMENDED))
>  
>  #define hv_get_crash_ctl(val) \
> @@ -271,6 +313,25 @@ int hv_unmap_ioapic_interrupt(int ioapic_id, struct hv_interrupt_entry *entry);
>  
>  int hv_set_mem_host_visibility(void *kbuffer, u32 size, u32 visibility);
>  int hv_mark_gpa_visibility(u16 count, const u64 pfn[], u32 visibility);
> +void hv_sint_wrmsrl_ghcb(u64 msr, u64 value);
> +void hv_sint_rdmsrl_ghcb(u64 msr, u64 *value);
> +void hv_signal_eom_ghcb(void);
> +void hv_ghcb_msr_write(u64 msr, u64 value);
> +void hv_ghcb_msr_read(u64 msr, u64 *value);
> +
> +#define hv_get_synint_state_ghcb(int_num, val)			\
> +	hv_sint_rdmsrl_ghcb(HV_X64_MSR_SINT0 + int_num, val)
> +#define hv_set_synint_state_ghcb(int_num, val) \
> +	hv_sint_wrmsrl_ghcb(HV_X64_MSR_SINT0 + int_num, val)
> +
> +#define hv_get_SIMP_ghcb(val) hv_sint_rdmsrl_ghcb(HV_X64_MSR_SIMP, val)
> +#define hv_set_SIMP_ghcb(val) hv_sint_wrmsrl_ghcb(HV_X64_MSR_SIMP, val)
> +
> +#define hv_get_SIEFP_ghcb(val) hv_sint_rdmsrl_ghcb(HV_X64_MSR_SIEFP, val)
> +#define hv_set_SIEFP_ghcb(val) hv_sint_wrmsrl_ghcb(HV_X64_MSR_SIEFP, val)
> +
> +#define hv_get_synic_state_ghcb(val) hv_sint_rdmsrl_ghcb(HV_X64_MSR_SCONTROL, val)
> +#define hv_set_synic_state_ghcb(val) hv_sint_wrmsrl_ghcb(HV_X64_MSR_SCONTROL, val)
>  #else /* CONFIG_HYPERV */
>  static inline void hyperv_init(void) {}
>  static inline void hyperv_setup_mmu_ops(void) {}
> @@ -289,9 +350,9 @@ static inline int hyperv_flush_guest_mapping_range(u64 as,
>  {
>  	return -1;
>  }
> +static inline void hv_signal_eom_ghcb(void) { };
>  #endif /* CONFIG_HYPERV */
>  
> -
>  #include <asm-generic/mshyperv.h>
>  
>  #endif
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index aeafd4017c89..6eaa0891c0f7 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -333,6 +333,9 @@ static void __init ms_hyperv_init_platform(void)
>  
>  		pr_info("Hyper-V: Isolation Config: Group A 0x%x, Group B 0x%x\n",
>  			ms_hyperv.isolation_config_a, ms_hyperv.isolation_config_b);
> +
> +		if (hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP)
> +			static_branch_enable(&isolation_type_snp);
>  	}
>  
>  	if (ms_hyperv.hints & HV_X64_ENLIGHTENED_VMCS_RECOMMENDED) {
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index f202ac7f4b3d..069530eeb7c6 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -99,17 +99,24 @@ int hv_synic_alloc(void)
>  		tasklet_init(&hv_cpu->msg_dpc,
>  			     vmbus_on_msg_dpc, (unsigned long) hv_cpu);
>  
> -		hv_cpu->synic_message_page =
> -			(void *)get_zeroed_page(GFP_ATOMIC);
> -		if (hv_cpu->synic_message_page == NULL) {
> -			pr_err("Unable to allocate SYNIC message page\n");
> -			goto err;
> -		}
> +		/*
> +		 * Synic message and event pages are allocated by paravisor.
> +		 * Skip these pages allocation here.
> +		 */
> +		if (!hv_isolation_type_snp()) {
> +			hv_cpu->synic_message_page =
> +				(void *)get_zeroed_page(GFP_ATOMIC);
> +			if (hv_cpu->synic_message_page == NULL) {
> +				pr_err("Unable to allocate SYNIC message page\n");
> +				goto err;
> +			}
>  
> -		hv_cpu->synic_event_page = (void *)get_zeroed_page(GFP_ATOMIC);
> -		if (hv_cpu->synic_event_page == NULL) {
> -			pr_err("Unable to allocate SYNIC event page\n");
> -			goto err;
> +			hv_cpu->synic_event_page =
> +				(void *)get_zeroed_page(GFP_ATOMIC);
> +			if (hv_cpu->synic_event_page == NULL) {
> +				pr_err("Unable to allocate SYNIC event page\n");
> +				goto err;
> +			}
>  		}
>  
>  		hv_cpu->post_msg_page = (void *)get_zeroed_page(GFP_ATOMIC);
> @@ -136,10 +143,17 @@ void hv_synic_free(void)
>  	for_each_present_cpu(cpu) {
>  		struct hv_per_cpu_context *hv_cpu
>  			= per_cpu_ptr(hv_context.cpu_context, cpu);
> +		free_page((unsigned long)hv_cpu->post_msg_page);
> +
> +		/*
> +		 * Synic message and event pages are allocated by paravisor.
> +		 * Skip free these pages here.
> +		 */
> +		if (hv_isolation_type_snp())
> +			continue;
>  
>  		free_page((unsigned long)hv_cpu->synic_event_page);
>  		free_page((unsigned long)hv_cpu->synic_message_page);
> -		free_page((unsigned long)hv_cpu->post_msg_page);
>  	}
>  
>  	kfree(hv_context.hv_numa_map);
> @@ -161,20 +175,36 @@ void hv_synic_enable_regs(unsigned int cpu)
>  	union hv_synic_sint shared_sint;
>  	union hv_synic_scontrol sctrl;
>  
> -	/* Setup the Synic's message page */
> +
> +	/* Setup the Synic's message. */
>  	hv_get_simp(simp.as_uint64);
>  	simp.simp_enabled = 1;
> -	simp.base_simp_gpa = virt_to_phys(hv_cpu->synic_message_page)
> -		>> HV_HYP_PAGE_SHIFT;
> +
> +	if (hv_isolation_type_snp()) {
> +		hv_cpu->synic_message_page
> +			= ioremap_cache(simp.base_simp_gpa << HV_HYP_PAGE_SHIFT,
> +					HV_HYP_PAGE_SIZE);
> +		if (!hv_cpu->synic_message_page)
> +			pr_err("Fail to map syinc message page.\n");
> +	} else {
> +		simp.base_simp_gpa = virt_to_phys(hv_cpu->synic_message_page)
> +			>> HV_HYP_PAGE_SHIFT;
> +	}
>  
>  	hv_set_simp(simp.as_uint64);
>  
>  	/* Setup the Synic's event page */
>  	hv_get_siefp(siefp.as_uint64);
>  	siefp.siefp_enabled = 1;
> -	siefp.base_siefp_gpa = virt_to_phys(hv_cpu->synic_event_page)
> -		>> HV_HYP_PAGE_SHIFT;
> -
> +	if (hv_isolation_type_snp()) {
> +		hv_cpu->synic_event_page = ioremap_cache(
> +			 siefp.base_siefp_gpa << HV_HYP_PAGE_SHIFT, HV_HYP_PAGE_SIZE);
> +		if (!hv_cpu->synic_event_page)
> +			pr_err("Fail to map syinc event page.\n");
> +	} else {
> +		siefp.base_siefp_gpa = virt_to_phys(hv_cpu->synic_event_page)
> +			>> HV_HYP_PAGE_SHIFT;
> +	}
>  	hv_set_siefp(siefp.as_uint64);
>  
>  	/* Setup the shared SINT. */
> @@ -188,7 +218,6 @@ void hv_synic_enable_regs(unsigned int cpu)
>  	/* Enable the global synic bit */
>  	hv_get_synic_state(sctrl.as_uint64);
>  	sctrl.enable = 1;
> -
>  	hv_set_synic_state(sctrl.as_uint64);
>  }
>  
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index b73e201abc70..59777377e641 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -23,6 +23,7 @@
>  #include <linux/bitops.h>
>  #include <linux/cpumask.h>
>  #include <asm/ptrace.h>
> +#include <asm/mshyperv.h>
>  #include <asm/hyperv-tlfs.h>
>  
>  struct ms_hyperv_info {
> @@ -52,7 +53,7 @@ extern struct ms_hyperv_info ms_hyperv;
>  
>  extern u64 hv_do_hypercall(u64 control, void *inputaddr, void *outputaddr);
>  extern u64 hv_do_fast_hypercall8(u16 control, u64 input8);
> -
> +extern bool hv_isolation_type_snp(void);
>  
>  /* Generate the guest OS identifier as described in the Hyper-V TLFS */
>  static inline  __u64 generate_guest_id(__u64 d_info1, __u64 kernel_version,
> @@ -186,6 +187,7 @@ bool hv_is_hyperv_initialized(void);
>  bool hv_is_hibernation_supported(void);
>  enum hv_isolation_type hv_get_isolation_type(void);
>  bool hv_is_isolation_supported(void);
> +bool hv_isolation_type_snp(void);
>  void hyperv_cleanup(void);
>  #else /* CONFIG_HYPERV */
>  static inline bool hv_is_hyperv_initialized(void) { return false; }
> -- 
> 2.25.1
>