Re: [PATCH v2 1/2] x86/mem_event: Deliver gla fault EPT violation information

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 07/08/2014 20:47, Tamas K Lengyel wrote:
> On Intel EPT the exit qualification generated by a violation also includes a bit (EPT_GLA_FAULT) which describes the following information:
> Set if the access causing the EPT violation is to a guest-physical address that is the translation of a linear address. Clear if the access causing the EPT violation is to a paging-structure entry as part of a page walk or the update of an accessed or dirty bit.
>
> For more information see Table 27-7 in the Intel SDM.
>
> This patch extends the mem_event system to deliver this extra information, which could be useful for determining the cause of a violation.
>
> v2: Split gla_fault into fault_in_gpt and fault_gla to be more compatible with the AMD implementation.
>
> Signed-off-by: Tamas K Lengyel <tamas.lengyel@zentific.com>
> ---
>  xen/arch/x86/hvm/hvm.c         |  8 ++++++--
>  xen/arch/x86/hvm/svm/svm.c     |  2 +-
>  xen/arch/x86/hvm/vmx/vmx.c     | 23 ++++++++++++++++++++++-
>  xen/arch/x86/mm/p2m.c          |  5 ++++-
>  xen/include/asm-x86/hvm/hvm.h  |  5 ++++-
>  xen/include/asm-x86/p2m.h      |  3 ++-
>  xen/include/public/mem_event.h |  4 +++-
>  7 files changed, 42 insertions(+), 8 deletions(-)
>
> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> index e834406..d7b5e2b 100644
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -2725,6 +2725,8 @@ void hvm_inject_page_fault(int errcode, unsigned long cr2)
>  int hvm_hap_nested_page_fault(paddr_t gpa,
>                                bool_t gla_valid,
>                                unsigned long gla,
> +                              bool_t fault_in_gpt,
> +                              bool_t fault_gla,
>                                bool_t access_r,
>                                bool_t access_w,
>                                bool_t access_x)
> @@ -2832,8 +2834,10 @@ int hvm_hap_nested_page_fault(paddr_t gpa,
>  
>          if ( violation )
>          {
> -            if ( p2m_mem_access_check(gpa, gla_valid, gla, access_r, 
> -                                        access_w, access_x, &req_ptr) )
> +            if ( p2m_mem_access_check(gpa, gla_valid, gla,
> +                                        fault_in_gpt, fault_gla,
> +                                        access_r, access_w, access_x,
> +                                        &req_ptr) )

Please fix your new indentation. 

>              {
>                  fall_through = 1;
>              } else {
> diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
> index 76616ac..9e35e7a 100644
> --- a/xen/arch/x86/hvm/svm/svm.c
> +++ b/xen/arch/x86/hvm/svm/svm.c
> @@ -1403,7 +1403,7 @@ static void svm_do_nested_pgfault(struct vcpu *v,
>      p2m_access_t p2ma;
>      struct p2m_domain *p2m = NULL;
>  
> -    ret = hvm_hap_nested_page_fault(gpa, 0, ~0ul, 
> +    ret = hvm_hap_nested_page_fault(gpa, 0, ~0ul, 0, 0,
>                                      1, /* All NPFs count as reads */
>                                      npfec & PFEC_write_access, 
>                                      npfec & PFEC_insn_fetch);
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> index 2caa04a..7ebf289 100644
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -2353,6 +2353,7 @@ static void ept_handle_violation(unsigned long qualification, paddr_t gpa)
>      p2m_type_t p2mt;
>      int ret;
>      struct domain *d = current->domain;
> +    bool_t fault_in_gpt, fault_gla;
>  
>      if ( tb_init_done )
>      {
> @@ -2371,11 +2372,31 @@ static void ept_handle_violation(unsigned long qualification, paddr_t gpa)
>      }
>  
>      if ( qualification & EPT_GLA_VALID )
> +    {
>          __vmread(GUEST_LINEAR_ADDRESS, &gla);
> +
> +        if ( qualification & EPT_GLA_FAULT )
> +        {
> +            fault_in_gpt = 0;
> +            fault_gla = 1;
> +        }
> +        else
> +        {
> +            fault_in_gpt = 1;
> +            fault_gla = 0;
> +        }

fault_gla = !!(qualification & EPT_GLA_FAULT);
fault_in_gpt = !fault_gla;

is rather shorter.

> +    }
>      else
> +    {
>          gla = ~0ull;
> +        fault_in_gpt = 0;
> +        fault_gla = 0;

These two could arguably be part of the same compound assignment.

> +    }
>      ret = hvm_hap_nested_page_fault(gpa,
> -                                    !!(qualification & EPT_GLA_VALID), gla,
> +                                    !!(qualification & EPT_GLA_VALID),
> +                                    gla,
> +                                    fault_in_gpt,
> +                                    fault_gla,

These three really should be following each other on the same line.

~Andrew

>                                      !!(qualification & EPT_READ_VIOLATION),
>                                      !!(qualification & EPT_WRITE_VIOLATION),
>                                      !!(qualification & EPT_EXEC_VIOLATION));
> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
> index bca9f0f..132f0d2 100644
> --- a/xen/arch/x86/mm/p2m.c
> +++ b/xen/arch/x86/mm/p2m.c
> @@ -1323,7 +1323,8 @@ void p2m_mem_paging_resume(struct domain *d)
>      }
>  }
>  
> -bool_t p2m_mem_access_check(paddr_t gpa, bool_t gla_valid, unsigned long gla, 
> +bool_t p2m_mem_access_check(paddr_t gpa, bool_t gla_valid, unsigned long gla,
> +                          bool_t fault_in_gpt, bool_t fault_gla,
>                            bool_t access_r, bool_t access_w, bool_t access_x,
>                            mem_event_request_t **req_ptr)
>  {
> @@ -1405,6 +1406,8 @@ bool_t p2m_mem_access_check(paddr_t gpa, bool_t gla_valid, unsigned long gla,
>          req->offset = gpa & ((1 << PAGE_SHIFT) - 1);
>          req->gla_valid = gla_valid;
>          req->gla = gla;
> +        req->fault_in_gpt = fault_in_gpt;
> +        req->fault_gla = fault_gla;
>          req->access_r = access_r;
>          req->access_w = access_w;
>          req->access_x = access_x;
> diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
> index 0ebd478..de755b6 100644
> --- a/xen/include/asm-x86/hvm/hvm.h
> +++ b/xen/include/asm-x86/hvm/hvm.h
> @@ -456,7 +456,10 @@ static inline void hvm_invalidate_regs_fields(struct cpu_user_regs *regs)
>  }
>  
>  int hvm_hap_nested_page_fault(paddr_t gpa,
> -                              bool_t gla_valid, unsigned long gla,
> +                              bool_t gla_valid,
> +                              unsigned long gla,
> +                              bool_t fault_in_gpt,
> +                              bool_t fault_gla,
>                                bool_t access_r,
>                                bool_t access_w,
>                                bool_t access_x);
> diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
> index 0ddbadb..59803c5 100644
> --- a/xen/include/asm-x86/p2m.h
> +++ b/xen/include/asm-x86/p2m.h
> @@ -597,7 +597,8 @@ void p2m_mem_paging_resume(struct domain *d);
>   * been promoted with no underlying vcpu pause. If the req_ptr has been populated, 
>   * then the caller must put the event in the ring (once having released get_gfn*
>   * locks -- caller must also xfree the request. */
> -bool_t p2m_mem_access_check(paddr_t gpa, bool_t gla_valid, unsigned long gla, 
> +bool_t p2m_mem_access_check(paddr_t gpa, bool_t gla_valid, unsigned long gla,
> +                          bool_t fault_in_gpt, bool_t fault_gla,
>                            bool_t access_r, bool_t access_w, bool_t access_x,
>                            mem_event_request_t **req_ptr);
>  /* Resumes the running of the VCPU, restarting the last instruction */
> diff --git a/xen/include/public/mem_event.h b/xen/include/public/mem_event.h
> index 3831b41..1ba6863 100644
> --- a/xen/include/public/mem_event.h
> +++ b/xen/include/public/mem_event.h
> @@ -62,7 +62,9 @@ typedef struct mem_event_st {
>      uint16_t access_w:1;
>      uint16_t access_x:1;
>      uint16_t gla_valid:1;
> -    uint16_t available:12;
> +    uint16_t fault_in_gpt:1;
> +    uint16_t fault_gla:1;
> +    uint16_t available:10;
>  
>      uint16_t reason;
>  } mem_event_request_t, mem_event_response_t;