Re: [PATCH v3 2/3] x86/HVM: add known_gla() emulation helper

[Paul Durrant <Paul.Durrant@citrix.com>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@suse.com]
> Sent: 06 September 2018 14:04
> To: xen-devel <xen-devel@lists.xenproject.org>
> Cc: Olaf Hering <olaf@aepfle.de>; Andrew Cooper
> <Andrew.Cooper3@citrix.com>; Paul Durrant <Paul.Durrant@citrix.com>
> Subject: [PATCH v3 2/3] x86/HVM: add known_gla() emulation helper
> 
> ... as a central place to do respective checking for whether the
> translation for the linear address is available as well as usable.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> ---
> v3: Split from subsequent patch.

Much nicer :-)

Reviewed-by: Paul Durrant <paul.durrant@citrix.com>

> 
> --- a/xen/arch/x86/hvm/emulate.c
> +++ b/xen/arch/x86/hvm/emulate.c
> @@ -1041,6 +1041,26 @@ static inline int hvmemul_linear_mmio_wr
>                                        pfec, hvmemul_ctxt, translate);
>  }
> 
> +static bool known_gla(unsigned long addr, unsigned int bytes, uint32_t
> pfec)
> +{
> +    const struct hvm_vcpu_io *vio = &current->arch.hvm.hvm_io;
> +
> +    if ( pfec & PFEC_write_access )
> +    {
> +        if ( !vio->mmio_access.write_access )
> +            return false;
> +    }
> +    else if ( pfec & PFEC_insn_fetch )
> +    {
> +        if ( !vio->mmio_access.insn_fetch )
> +            return false;
> +    }
> +    else if ( !vio->mmio_access.read_access )
> +            return false;
> +
> +    return vio->mmio_gla == (addr & PAGE_MASK);
> +}
> +
>  static int __hvmemul_read(
>      enum x86_segment seg,
>      unsigned long offset,
> @@ -1049,11 +1069,9 @@ static int __hvmemul_read(
>      enum hvm_access_type access_type,
>      struct hvm_emulate_ctxt *hvmemul_ctxt)
>  {
> -    struct vcpu *curr = current;
>      pagefault_info_t pfinfo;
>      unsigned long addr, reps = 1;
>      uint32_t pfec = PFEC_page_present;
> -    struct hvm_vcpu_io *vio = &curr->arch.hvm.hvm_io;
>      int rc;
> 
>      if ( is_x86_system_segment(seg) )
> @@ -1067,10 +1085,7 @@ static int __hvmemul_read(
>          seg, offset, bytes, &reps, access_type, hvmemul_ctxt, &addr);
>      if ( rc != X86EMUL_OKAY || !bytes )
>          return rc;
> -    if ( ((access_type != hvm_access_insn_fetch
> -           ? vio->mmio_access.read_access
> -           : vio->mmio_access.insn_fetch)) &&
> -         (vio->mmio_gla == (addr & PAGE_MASK)) )
> +    if ( known_gla(addr, bytes, pfec) )
>          return hvmemul_linear_mmio_read(addr, bytes, p_data, pfec,
> hvmemul_ctxt, 1);
> 
>      rc = hvm_copy_from_guest_linear(p_data, addr, bytes, pfec, &pfinfo);
> @@ -1171,10 +1186,8 @@ static int hvmemul_write(
>  {
>      struct hvm_emulate_ctxt *hvmemul_ctxt =
>          container_of(ctxt, struct hvm_emulate_ctxt, ctxt);
> -    struct vcpu *curr = current;
>      unsigned long addr, reps = 1;
>      uint32_t pfec = PFEC_page_present | PFEC_write_access;
> -    struct hvm_vcpu_io *vio = &curr->arch.hvm.hvm_io;
>      int rc;
>      void *mapping;
> 
> @@ -1188,8 +1201,7 @@ static int hvmemul_write(
>      if ( rc != X86EMUL_OKAY || !bytes )
>          return rc;
> 
> -    if ( vio->mmio_access.write_access &&
> -         (vio->mmio_gla == (addr & PAGE_MASK)) )
> +    if ( known_gla(addr, bytes, pfec) )
>          return hvmemul_linear_mmio_write(addr, bytes, p_data, pfec,
> hvmemul_ctxt, 1);
> 
>      mapping = hvmemul_map_linear_addr(addr, bytes, pfec, hvmemul_ctxt);
> @@ -1218,7 +1230,6 @@ static int hvmemul_rmw(
>          container_of(ctxt, struct hvm_emulate_ctxt, ctxt);
>      unsigned long addr, reps = 1;
>      uint32_t pfec = PFEC_page_present | PFEC_write_access;
> -    struct hvm_vcpu_io *vio = &current->arch.hvm.hvm_io;
>      int rc;
>      void *mapping;
> 
> @@ -1244,8 +1255,7 @@ static int hvmemul_rmw(
>      else
>      {
>          unsigned long data = 0;
> -        bool known_gpfn = vio->mmio_access.write_access &&
> -                          vio->mmio_gla == (addr & PAGE_MASK);
> +        bool known_gpfn = known_gla(addr, bytes, pfec);
> 
>          if ( bytes > sizeof(data) )
>              return X86EMUL_UNHANDLEABLE;
> 
> 
> 


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