Re: [Xen-devel] [PATCH v3 19/25] x86emul: tell cmpxchg hook whether LOCK is in effect

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: 07 December 2017 14:14
> To: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
> Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; Paul Durrant
> <Paul.Durrant@xxxxxxxxxx>; George Dunlap <George.Dunlap@xxxxxxxxxx>;
> Tim (Xen.org) <tim@xxxxxxx>
> Subject: [PATCH v3 19/25] x86emul: tell cmpxchg hook whether LOCK is in
> effect
> 
> This is necessary for the hook to correctly perform the operation.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

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

> ---
> v3: New.
> 
> --- a/tools/fuzz/x86_instruction_emulator/fuzz-emul.c
> +++ b/tools/fuzz/x86_instruction_emulator/fuzz-emul.c
> @@ -346,6 +346,7 @@ static int fuzz_cmpxchg(
>      void *old,
>      void *new,
>      unsigned int bytes,
> +    bool lock,
>      struct x86_emulate_ctxt *ctxt)
>  {
>      /*
> --- a/tools/tests/x86_emulator/test_x86_emulator.c
> +++ b/tools/tests/x86_emulator/test_x86_emulator.c
> @@ -320,6 +320,7 @@ static int cmpxchg(
>      void *old,
>      void *new,
>      unsigned int bytes,
> +    bool lock,
>      struct x86_emulate_ctxt *ctxt)
>  {
>      if ( verbose )
> --- a/xen/arch/x86/hvm/emulate.c
> +++ b/xen/arch/x86/hvm/emulate.c
> @@ -1249,6 +1249,7 @@ static int hvmemul_cmpxchg_discard(
>      void *p_old,
>      void *p_new,
>      unsigned int bytes,
> +    bool lock,
>      struct x86_emulate_ctxt *ctxt)
>  {
>      return X86EMUL_OKAY;
> @@ -1292,6 +1293,7 @@ static int hvmemul_cmpxchg(
>      void *p_old,
>      void *p_new,
>      unsigned int bytes,
> +    bool lock,
>      struct x86_emulate_ctxt *ctxt)
>  {
>      /* Fix this in case the guest is really relying on r-m-w atomicity. */
> --- a/xen/arch/x86/mm/shadow/common.c
> +++ b/xen/arch/x86/mm/shadow/common.c
> @@ -281,6 +281,7 @@ hvm_emulate_cmpxchg(enum x86_segment seg
>                      void *p_old,
>                      void *p_new,
>                      unsigned int bytes,
> +                    bool lock,
>                      struct x86_emulate_ctxt *ctxt)
>  {
>      struct sh_emulate_ctxt *sh_ctxt =
> --- a/xen/arch/x86/pv/ro-page-fault.c
> +++ b/xen/arch/x86/pv/ro-page-fault.c
> @@ -216,7 +216,7 @@ static int ptwr_emulated_write(enum x86_
> 
>  static int ptwr_emulated_cmpxchg(enum x86_segment seg, unsigned long
> offset,
>                                   void *p_old, void *p_new, unsigned int 
> bytes,
> -                                 struct x86_emulate_ctxt *ctxt)
> +                                 bool lock, struct x86_emulate_ctxt *ctxt)
>  {
>      paddr_t old = 0, new = 0;
> 
> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
> @@ -1973,7 +1973,7 @@ protmode_load_seg(
> 
>          fail_if(!ops->cmpxchg);
>          switch ( (rc = ops->cmpxchg(sel_seg, (sel & 0xfff8) + 4, &desc.b,
> -                                    &new_desc_b, sizeof(desc.b), ctxt)) )
> +                                    &new_desc_b, sizeof(desc.b), true, 
> ctxt)) )
>          {
>          case X86EMUL_OKAY:
>              break;
> @@ -6982,7 +6982,8 @@ x86_emulate(
>              }
> 
>              if ( (rc = ops->cmpxchg(ea.mem.seg, ea.mem.off, old, aux,
> -                                    op_bytes, ctxt)) != X86EMUL_OKAY )
> +                                    op_bytes, lock_prefix,
> +                                    ctxt)) != X86EMUL_OKAY )
>                  goto done;
>              _regs.eflags |= X86_EFLAGS_ZF;
>          }
> @@ -8434,7 +8435,7 @@ x86_emulate(
>              fail_if(!ops->cmpxchg);
>              rc = ops->cmpxchg(
>                  dst.mem.seg, dst.mem.off, &dst.orig_val,
> -                &dst.val, dst.bytes, ctxt);
> +                &dst.val, dst.bytes, true, ctxt);
>          }
>          else
>          {
> --- a/xen/arch/x86/x86_emulate/x86_emulate.h
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.h
> @@ -237,10 +237,11 @@ struct x86_emulate_ops
>          struct x86_emulate_ctxt *ctxt);
> 
>      /*
> -     * cmpxchg: Emulate an atomic (LOCKed) CMPXCHG operation.
> +     * cmpxchg: Emulate a CMPXCHG operation.
>       *  @p_old: [IN ] Pointer to value expected to be current at @addr.
>       *  @p_new: [IN ] Pointer to value to write to @addr.
>       *  @bytes: [IN ] Operation size (up to 8 (x86/32) or 16 (x86/64) bytes).
> +     *  @lock:  [IN ] atomic (LOCKed) operation
>       */
>      int (*cmpxchg)(
>          enum x86_segment seg,
> @@ -248,6 +249,7 @@ struct x86_emulate_ops
>          void *p_old,
>          void *p_new,
>          unsigned int bytes,
> +        bool lock,
>          struct x86_emulate_ctxt *ctxt);
> 
>      /*
> 


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