Re: [PATCH v3 09/28] xen/vm_event: consolidate CONFIG_VM_EVENT

[Grygorii Strashko <grygorii_strashko@epam.com>]

Hi

On 13.10.25 13:15, Penny Zheng wrote:
> File hvm/vm_event.c and x86/vm_event.c are the extend to vm_event handling
> routines, and its compilation shall be guarded by CONFIG_VM_EVENT too.
> Futhermore, features about monitor_op and memory access are both based on
> vm event subsystem, so monitor.o/mem_access.o shall be wrapped under
> CONFIG_VM_EVENT.
> 
> Although CONFIG_VM_EVENT is right now forcibly enabled on x86 via
> MEM_ACCESS_ALWAYS_ON, we could disable it through disabling
> CONFIG_MGMT_HYPERCALLS later. So we remove MEM_ACCESS_ALWAYS_ON and
> make VM_EVENT=y on default only on x86 to retain the same.
> 
> In consequence, a few switch-blocks need in-place stubs in do_altp2m_op()
> to pass compilation when ALTP2M=y and VM_EVENT=n(, hence MEM_ACCESS=n), like
> HVMOP_altp2m_set_mem_access, etc.
> And the following functions still require stubs to pass compilation:
> - vm_event_check_ring()
> - p2m_mem_access_check()
> - xenmem_access_to_p2m_access()
> 
> The following functions are developed on the basis of vm event framework, or
> only invoked by vm_event.c/monitor.c/mem_access.c, so they all shall be
> wrapped with CONFIG_VM_EVENT (otherwise they will become unreachable and
> violate Misra rule 2.1 when VM_EVENT=n):
> - hvm_toggle_singlestep
> - hvm_fast_singlestep
> - hvm_enable_msr_interception
>    - hvm_function_table.enable_msr_interception
> - hvm_has_set_descriptor_access_existing
>    - hvm_function_table.set_descriptor_access_existing
> - arch_monitor_domctl_op
> - arch_monitor_allow_userspace
> - arch_monitor_get_capabilities
> - hvm_emulate_one_vm_event
> - hvmemul_write{,cmpxchg,rep_ins,rep_outs,rep_movs,rep_stos,read_io,write_io}_discard
> 
> Signed-off-by: Penny Zheng <Penny.Zheng@amd.com>
> ---
> v1 -> v2:
> - split out XSM changes
> - remove unnecessary stubs
> - move "struct p2m_domain" declaration ahead of the #ifdef
> ---
> v2 -> v3:
> - move .enable_msr_interception and .set_descriptor_access_exiting together
> - with the introduction of "vm_event_is_enabled()", all hvm_monitor_xxx()
> stubs are no longer needed
> - change to use in-place stubs in do_altp2m_op()
> - no need to add stub for monitor_traps(), __vm_event_claim_slot(),
> vm_event_put_request() and vm_event_vcpu_pause()
> - remove MEM_ACCESS_ALWAYS_ON
> - return default p2m_access_rwx for xenmem_access_to_p2m_access() when
> VM_EVENT=n
> - add wrapping for hvm_emulate_one_vm_event/
> hvmemul_write{,cmpxchg,rep_ins,rep_outs,rep_movs,rep_stos,read_io,write_io}_discard
> ---
>   xen/arch/x86/Makefile                 |  2 +-
>   xen/arch/x86/hvm/Kconfig              |  1 -
>   xen/arch/x86/hvm/Makefile             |  4 +-
>   xen/arch/x86/hvm/emulate.c            | 58 ++++++++++++++-------------
>   xen/arch/x86/hvm/hvm.c                | 21 ++++++++++
>   xen/arch/x86/hvm/svm/svm.c            |  8 +++-
>   xen/arch/x86/hvm/vmx/vmx.c            | 10 +++++
>   xen/arch/x86/include/asm/hvm/hvm.h    |  9 ++++-
>   xen/arch/x86/include/asm/mem_access.h |  9 +++++
>   xen/arch/x86/include/asm/monitor.h    |  9 +++++
>   xen/common/Kconfig                    |  7 +---
>   xen/include/xen/mem_access.h          | 10 +++++
>   xen/include/xen/vm_event.h            |  7 ++++
>   13 files changed, 116 insertions(+), 39 deletions(-)
> 
> diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
> index 0f91ffcb9d..615cd101b8 100644
> --- a/xen/arch/x86/Makefile
> +++ b/xen/arch/x86/Makefile
> @@ -76,7 +76,7 @@ obj-y += usercopy.o
>   obj-y += x86_emulate.o
>   obj-$(CONFIG_TBOOT) += tboot.o
>   obj-y += hpet.o
> -obj-y += vm_event.o
> +obj-$(CONFIG_VM_EVENT) += vm_event.o
>   obj-y += xstate.o
>   
>   ifneq ($(CONFIG_PV_SHIM_EXCLUSIVE),y)
> diff --git a/xen/arch/x86/hvm/Kconfig b/xen/arch/x86/hvm/Kconfig
> index 5cb9f29042..e6b388dd0e 100644
> --- a/xen/arch/x86/hvm/Kconfig
> +++ b/xen/arch/x86/hvm/Kconfig
> @@ -3,7 +3,6 @@ menuconfig HVM
>   	default !PV_SHIM
>   	select COMPAT
>   	select IOREQ_SERVER
> -	select MEM_ACCESS_ALWAYS_ON
>   	help
>   	  Interfaces to support HVM domains.  HVM domains require hardware
>   	  virtualisation extensions (e.g. Intel VT-x, AMD SVM), but can boot
> diff --git a/xen/arch/x86/hvm/Makefile b/xen/arch/x86/hvm/Makefile
> index 6ec2c8f2db..952db00dd7 100644
> --- a/xen/arch/x86/hvm/Makefile
> +++ b/xen/arch/x86/hvm/Makefile
> @@ -16,7 +16,7 @@ obj-y += io.o
>   obj-y += ioreq.o
>   obj-y += irq.o
>   obj-y += mmio.o
> -obj-y += monitor.o
> +obj-$(CONFIG_VM_EVENT) += monitor.o
>   obj-y += mtrr.o
>   obj-y += nestedhvm.o
>   obj-y += pmtimer.o
> @@ -26,7 +26,7 @@ obj-y += save.o
>   obj-y += stdvga.o
>   obj-y += vioapic.o
>   obj-y += vlapic.o
> -obj-y += vm_event.o
> +obj-$(CONFIG_VM_EVENT) += vm_event.o
>   obj-y += vmsi.o
>   obj-y += vpic.o
>   obj-y += vpt.o
> diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
> index fe75b0516d..d56ef02baf 100644
> --- a/xen/arch/x86/hvm/emulate.c
> +++ b/xen/arch/x86/hvm/emulate.c
> @@ -1615,6 +1615,7 @@ static int cf_check hvmemul_blk(
>       return rc;
>   }
>   
> +#ifdef CONFIG_VM_EVENT
>   static int cf_check hvmemul_write_discard(
>       enum x86_segment seg,
>       unsigned long offset,
> @@ -1717,6 +1718,7 @@ static int cf_check hvmemul_cache_op_discard(
>   {
>       return X86EMUL_OKAY;
>   }
> +#endif /* CONFIG_VM_EVENT */
>   
>   static int cf_check hvmemul_cmpxchg(
>       enum x86_segment seg,
> @@ -2750,33 +2752,6 @@ static const struct x86_emulate_ops hvm_emulate_ops = {
>       .vmfunc        = hvmemul_vmfunc,
>   };
>   
> -static const struct x86_emulate_ops hvm_emulate_ops_no_write = {
> -    .read          = hvmemul_read,
> -    .insn_fetch    = hvmemul_insn_fetch,
> -    .write         = hvmemul_write_discard,
> -    .cmpxchg       = hvmemul_cmpxchg_discard,
> -    .rep_ins       = hvmemul_rep_ins_discard,
> -    .rep_outs      = hvmemul_rep_outs_discard,
> -    .rep_movs      = hvmemul_rep_movs_discard,
> -    .rep_stos      = hvmemul_rep_stos_discard,
> -    .read_segment  = hvmemul_read_segment,
> -    .write_segment = hvmemul_write_segment,
> -    .read_io       = hvmemul_read_io_discard,
> -    .write_io      = hvmemul_write_io_discard,
> -    .read_cr       = hvmemul_read_cr,
> -    .write_cr      = hvmemul_write_cr,
> -    .read_xcr      = hvmemul_read_xcr,
> -    .write_xcr     = hvmemul_write_xcr,
> -    .read_msr      = hvmemul_read_msr,
> -    .write_msr     = hvmemul_write_msr_discard,
> -    .cache_op      = hvmemul_cache_op_discard,
> -    .tlb_op        = hvmemul_tlb_op,
> -    .cpuid         = x86emul_cpuid,
> -    .get_fpu       = hvmemul_get_fpu,
> -    .put_fpu       = hvmemul_put_fpu,
> -    .vmfunc        = hvmemul_vmfunc,
> -};
> -
>   /*
>    * Note that passing VIO_no_completion into this function serves as kind
>    * of (but not fully) an "auto select completion" indicator.  When there's
> @@ -2887,6 +2862,34 @@ int hvm_emulate_one(
>       return _hvm_emulate_one(hvmemul_ctxt, &hvm_emulate_ops, completion);
>   }
>   
> +#ifdef CONFIG_VM_EVENT
> +static const struct x86_emulate_ops hvm_emulate_ops_no_write = {
> +    .read          = hvmemul_read,
> +    .insn_fetch    = hvmemul_insn_fetch,
> +    .write         = hvmemul_write_discard,
> +    .cmpxchg       = hvmemul_cmpxchg_discard,
> +    .rep_ins       = hvmemul_rep_ins_discard,
> +    .rep_outs      = hvmemul_rep_outs_discard,
> +    .rep_movs      = hvmemul_rep_movs_discard,
> +    .rep_stos      = hvmemul_rep_stos_discard,
> +    .read_segment  = hvmemul_read_segment,
> +    .write_segment = hvmemul_write_segment,
> +    .read_io       = hvmemul_read_io_discard,
> +    .write_io      = hvmemul_write_io_discard,
> +    .read_cr       = hvmemul_read_cr,
> +    .write_cr      = hvmemul_write_cr,
> +    .read_xcr      = hvmemul_read_xcr,
> +    .write_xcr     = hvmemul_write_xcr,
> +    .read_msr      = hvmemul_read_msr,
> +    .write_msr     = hvmemul_write_msr_discard,
> +    .cache_op      = hvmemul_cache_op_discard,
> +    .tlb_op        = hvmemul_tlb_op,
> +    .cpuid         = x86emul_cpuid,
> +    .get_fpu       = hvmemul_get_fpu,
> +    .put_fpu       = hvmemul_put_fpu,
> +    .vmfunc        = hvmemul_vmfunc,
> +};
> +
>   void hvm_emulate_one_vm_event(enum emul_kind kind, unsigned int trapnr,
>       unsigned int errcode)
>   {
> @@ -2949,6 +2952,7 @@ void hvm_emulate_one_vm_event(enum emul_kind kind, unsigned int trapnr,
>   
>       hvm_emulate_writeback(&ctx);
>   }
> +#endif /* CONFIG_VM_EVENT */
>   
>   void hvm_emulate_init_once(
>       struct hvm_emulate_ctxt *hvmemul_ctxt,
> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> index 48a293069b..e3dacc909b 100644
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -50,6 +50,7 @@
>   #include <asm/hvm/vm_event.h>
>   #include <asm/hvm/vpt.h>
>   #include <asm/i387.h>
> +#include <asm/mem_access.h>
>   #include <asm/mc146818rtc.h>
>   #include <asm/mce.h>
>   #include <asm/monitor.h>
> @@ -4861,15 +4862,20 @@ static int do_altp2m_op(
>           break;
>   
>       case HVMOP_altp2m_set_mem_access:
> +#ifdef CONFIG_VM_EVENT
>           if ( a.u.mem_access.pad )
>               rc = -EINVAL;
>           else
>               rc = p2m_set_mem_access(d, _gfn(a.u.mem_access.gfn), 1, 0, 0,
>                                       a.u.mem_access.access,
>                                       a.u.mem_access.view);
> +#else
> +        rc = -EOPNOTSUPP;
> +#endif
>           break;
>   
>       case HVMOP_altp2m_set_mem_access_multi:
> +#ifdef CONFIG_VM_EVENT
>           if ( a.u.set_mem_access_multi.pad ||
>                a.u.set_mem_access_multi.opaque > a.u.set_mem_access_multi.nr )
>           {
> @@ -4898,9 +4904,13 @@ static int do_altp2m_op(
>                                          &a, u.set_mem_access_multi.opaque) )
>                   rc = -EFAULT;
>           }
> +#else
> +        rc = -EOPNOTSUPP;
> +#endif
>           break;
>   
>       case HVMOP_altp2m_get_mem_access:
> +#ifdef CONFIG_VM_EVENT
>           if ( a.u.mem_access.pad )
>               rc = -EINVAL;
>           else
> @@ -4915,6 +4925,9 @@ static int do_altp2m_op(
>                   rc = __copy_to_guest(arg, &a, 1) ? -EFAULT : 0;
>               }
>           }
> +#else
> +        rc = -EOPNOTSUPP;
> +#endif
>           break;
>   
>       case HVMOP_altp2m_change_gfn:
> @@ -5030,6 +5043,7 @@ static int compat_altp2m_op(
>       switch ( a.cmd )
>       {
>       case HVMOP_altp2m_set_mem_access_multi:
> +#ifdef CONFIG_VM_EVENT
>   #define XLAT_hvm_altp2m_set_mem_access_multi_HNDL_pfn_list(_d_, _s_); \
>           guest_from_compat_handle((_d_)->pfn_list, (_s_)->pfn_list)
>   #define XLAT_hvm_altp2m_set_mem_access_multi_HNDL_access_list(_d_, _s_); \
> @@ -5038,6 +5052,7 @@ static int compat_altp2m_op(
>                                                &a.u.set_mem_access_multi);
>   #undef XLAT_hvm_altp2m_set_mem_access_multi_HNDL_pfn_list
>   #undef XLAT_hvm_altp2m_set_mem_access_multi_HNDL_access_list
> +#endif
>           break;
>   
>       default:
> @@ -5056,6 +5071,7 @@ static int compat_altp2m_op(
>       switch ( a.cmd )
>       {
>       case HVMOP_altp2m_set_mem_access_multi:
> +#ifdef CONFIG_VM_EVENT
>           if ( rc == -ERESTART )
>           {
>               a.u.set_mem_access_multi.opaque =
> @@ -5065,6 +5081,9 @@ static int compat_altp2m_op(
>                                          &a, u.set_mem_access_multi.opaque) )
>                   rc = -EFAULT;
>           }
> +#else
> +        rc = -EOPNOTSUPP;
> +#endif
>           break;
>   
>       default:
> @@ -5283,6 +5302,7 @@ int hvm_debug_op(struct vcpu *v, int32_t op)
>       return rc;
>   }
>   
> +#ifdef CONFIG_VM_EVENT
>   void hvm_toggle_singlestep(struct vcpu *v)
>   {
>       ASSERT(atomic_read(&v->pause_count));
> @@ -5292,6 +5312,7 @@ void hvm_toggle_singlestep(struct vcpu *v)
>   
>       v->arch.hvm.single_step = !v->arch.hvm.single_step;
>   }
> +#endif /* CONFIG_VM_EVENT */
>   
>   #ifdef CONFIG_ALTP2M
>   void hvm_fast_singlestep(struct vcpu *v, uint16_t p2midx)
> diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
> index 679ca3dacd..c8506c25c4 100644
> --- a/xen/arch/x86/hvm/svm/svm.c
> +++ b/xen/arch/x86/hvm/svm/svm.c
> @@ -299,6 +299,7 @@ void svm_intercept_msr(struct vcpu *v, uint32_t msr, int flags)
>           __clear_bit(msr * 2 + 1, msr_bit);
>   }
>   
> +#ifdef CONFIG_VM_EVENT
>   static void cf_check svm_enable_msr_interception(struct domain *d, uint32_t msr)
>   {
>       struct vcpu *v;
> @@ -306,6 +307,7 @@ static void cf_check svm_enable_msr_interception(struct domain *d, uint32_t msr)
>       for_each_vcpu ( d, v )
>           svm_intercept_msr(v, msr, MSR_INTERCEPT_WRITE);
>   }
> +#endif /* CONFIG_VM_EVENT */
>   
>   static void svm_save_dr(struct vcpu *v)
>   {
> @@ -826,6 +828,7 @@ static void cf_check svm_set_rdtsc_exiting(struct vcpu *v, bool enable)
>       vmcb_set_general2_intercepts(vmcb, general2_intercepts);
>   }
>   
> +#ifdef CONFIG_VM_EVENT
>   static void cf_check svm_set_descriptor_access_exiting(
>       struct vcpu *v, bool enable)
>   {
> @@ -843,6 +846,7 @@ static void cf_check svm_set_descriptor_access_exiting(
>   
>       vmcb_set_general1_intercepts(vmcb, general1_intercepts);
>   }
> +#endif /* CONFIG_VM_EVENT */
>   
>   static unsigned int cf_check svm_get_insn_bytes(struct vcpu *v, uint8_t *buf)
>   {
> @@ -2457,9 +2461,11 @@ static struct hvm_function_table __initdata_cf_clobber svm_function_table = {
>       .fpu_dirty_intercept  = svm_fpu_dirty_intercept,
>       .msr_read_intercept   = svm_msr_read_intercept,
>       .msr_write_intercept  = svm_msr_write_intercept,
> +#ifdef CONFIG_VM_EVENT
>       .enable_msr_interception = svm_enable_msr_interception,
> -    .set_rdtsc_exiting    = svm_set_rdtsc_exiting,
>       .set_descriptor_access_exiting = svm_set_descriptor_access_exiting,
> +#endif
> +    .set_rdtsc_exiting    = svm_set_rdtsc_exiting,
>       .get_insn_bytes       = svm_get_insn_bytes,
>   
>       .nhvm_vcpu_initialise = nsvm_vcpu_initialise,
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> index a40af1db66..1996e139a0 100644
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -1520,6 +1520,7 @@ static void cf_check vmx_set_rdtsc_exiting(struct vcpu *v, bool enable)
>       vmx_vmcs_exit(v);
>   }
>   
> +#ifdef CONFIG_VM_EVENT
>   static void cf_check vmx_set_descriptor_access_exiting(
>       struct vcpu *v, bool enable)
>   {
> @@ -1534,6 +1535,7 @@ static void cf_check vmx_set_descriptor_access_exiting(
>       vmx_update_secondary_exec_control(v);
>       vmx_vmcs_exit(v);
>   }
> +#endif /* CONFIG_VM_EVENT */
>   
>   static void cf_check vmx_init_hypercall_page(void *p)
>   {
> @@ -2413,6 +2415,7 @@ static void cf_check vmx_handle_eoi(uint8_t vector, int isr)
>           printk_once(XENLOG_WARNING "EOI for %02x but SVI=%02x\n", vector, old_svi);
>   }
>   
> +#ifdef CONFIG_VM_EVENT
>   static void cf_check vmx_enable_msr_interception(struct domain *d, uint32_t msr)
>   {
>       struct vcpu *v;
> @@ -2420,6 +2423,7 @@ static void cf_check vmx_enable_msr_interception(struct domain *d, uint32_t msr)
>       for_each_vcpu ( d, v )
>           vmx_set_msr_intercept(v, msr, VMX_MSR_W);
>   }
> +#endif /* CONFIG_VM_EVENT */
>   
>   #ifdef CONFIG_ALTP2M
>   
> @@ -2871,7 +2875,9 @@ static struct hvm_function_table __initdata_cf_clobber vmx_function_table = {
>       .nhvm_domain_relinquish_resources = nvmx_domain_relinquish_resources,
>       .update_vlapic_mode = vmx_vlapic_msr_changed,
>       .nhvm_hap_walk_L1_p2m = nvmx_hap_walk_L1_p2m,
> +#ifdef CONFIG_VM_EVENT
>       .enable_msr_interception = vmx_enable_msr_interception,
> +#endif
>   #ifdef CONFIG_ALTP2M
>       .altp2m_vcpu_update_p2m = vmx_vcpu_update_eptp,
>       .altp2m_vcpu_update_vmfunc_ve = vmx_vcpu_update_vmfunc_ve,
> @@ -3079,9 +3085,11 @@ const struct hvm_function_table * __init start_vmx(void)
>   
>       vmx_function_table.caps.singlestep = cpu_has_monitor_trap_flag;
>   
> +#ifdef CONFIG_VM_EVENT
>       if ( cpu_has_vmx_dt_exiting )
>           vmx_function_table.set_descriptor_access_exiting =
>               vmx_set_descriptor_access_exiting;
> +#endif
>   
>       /*
>        * Do not enable EPT when (!cpu_has_vmx_pat), to prevent security hole
> @@ -3152,8 +3160,10 @@ void __init vmx_fill_funcs(void)
>       if ( !cpu_has_xen_ibt )
>           return;
>   
> +#ifdef CONFIG_VM_EVENT
>       vmx_function_table.set_descriptor_access_exiting =
>           vmx_set_descriptor_access_exiting;
> +#endif
>   
>       vmx_function_table.update_eoi_exit_bitmap = vmx_update_eoi_exit_bitmap;
>       vmx_function_table.process_isr            = vmx_process_isr;
> diff --git a/xen/arch/x86/include/asm/hvm/hvm.h b/xen/arch/x86/include/asm/hvm/hvm.h
> index f02183691e..473cf24b83 100644
> --- a/xen/arch/x86/include/asm/hvm/hvm.h
> +++ b/xen/arch/x86/include/asm/hvm/hvm.h
> @@ -192,7 +192,10 @@ struct hvm_function_table {
>       void (*handle_cd)(struct vcpu *v, unsigned long value);
>       void (*set_info_guest)(struct vcpu *v);
>       void (*set_rdtsc_exiting)(struct vcpu *v, bool enable);
> +#ifdef CONFIG_VM_EVENT
>       void (*set_descriptor_access_exiting)(struct vcpu *v, bool enable);
> +    void (*enable_msr_interception)(struct domain *d, uint32_t msr);
> +#endif
>   
>       /* Nested HVM */
>       int (*nhvm_vcpu_initialise)(struct vcpu *v);
> @@ -224,8 +227,6 @@ struct hvm_function_table {
>                                   paddr_t *L1_gpa, unsigned int *page_order,
>                                   uint8_t *p2m_acc, struct npfec npfec);
>   
> -    void (*enable_msr_interception)(struct domain *d, uint32_t msr);
> -
>   #ifdef CONFIG_ALTP2M
>       /* Alternate p2m */
>       void (*altp2m_vcpu_update_p2m)(struct vcpu *v);
> @@ -433,10 +434,12 @@ static inline bool using_svm(void)
>   
>   #define hvm_long_mode_active(v) (!!((v)->arch.hvm.guest_efer & EFER_LMA))
>   
> +#ifdef CONFIG_VM_EVENT
>   static inline bool hvm_has_set_descriptor_access_exiting(void)
>   {
>       return hvm_funcs.set_descriptor_access_exiting;
>   }
> +#endif
>   
>   static inline void hvm_domain_creation_finished(struct domain *d)
>   {
> @@ -679,10 +682,12 @@ static inline int nhvm_hap_walk_L1_p2m(
>           v, L2_gpa, L1_gpa, page_order, p2m_acc, npfec);
>   }
>   
> +#ifdef CONFIG_VM_EVENT
>   static inline void hvm_enable_msr_interception(struct domain *d, uint32_t msr)
>   {
>       alternative_vcall(hvm_funcs.enable_msr_interception, d, msr);
>   }
> +#endif
>   
>   static inline bool hvm_is_singlestep_supported(void)
>   {
> diff --git a/xen/arch/x86/include/asm/mem_access.h b/xen/arch/x86/include/asm/mem_access.h
> index 1a52a10322..c786116310 100644
> --- a/xen/arch/x86/include/asm/mem_access.h
> +++ b/xen/arch/x86/include/asm/mem_access.h
> @@ -14,6 +14,7 @@
>   #ifndef __ASM_X86_MEM_ACCESS_H__
>   #define __ASM_X86_MEM_ACCESS_H__
>   
> +#ifdef CONFIG_VM_EVENT
>   /*
>    * Setup vm_event request based on the access (gla is -1ull if not available).
>    * Handles the rw2rx conversion. Boolean return value indicates if event type
> @@ -25,6 +26,14 @@
>   bool p2m_mem_access_check(paddr_t gpa, unsigned long gla,
>                             struct npfec npfec,
>                             struct vm_event_st **req_ptr);
> +#else
> +static inline bool p2m_mem_access_check(paddr_t gpa, unsigned long gla,
> +                                        struct npfec npfec,
> +                                        struct vm_event_st **req_ptr)
> +{
> +    return false;
> +}
> +#endif /* CONFIG_VM_EVENT */
>   
>   /* Check for emulation and mark vcpu for skipping one instruction
>    * upon rescheduling if required. */
> diff --git a/xen/arch/x86/include/asm/monitor.h b/xen/arch/x86/include/asm/monitor.h
> index 3c64d8258f..1cd169f8f0 100644
> --- a/xen/arch/x86/include/asm/monitor.h
> +++ b/xen/arch/x86/include/asm/monitor.h
> @@ -32,6 +32,7 @@ struct monitor_msr_bitmap {
>       DECLARE_BITMAP(high, 8192);
>   };
>   
> +#ifdef COMFIG_VM_EVENT

Typo here causes build to fail.

With ^ fixed and patches 3 and 9 applied, and VM_EVENT=n there are still
build failures, like:

   xen/arch/x86/hvm/svm/svm.c:2757: undefined reference to `hvm_monitor_debug'

In my opinion, It might be reasonable to proceed with this patch (and related patches [3,?]) first,
as standalone series, to make VM_EVENT=n work and do MGMT_HYPERCALLS on top of it.

This patch, by itself, is big and included in even bigger series - which makes hard to
review and track changes.

[..]

-- 
Best regards,
-grygorii