[Xen-devel] Ping: [PATCH] x86/HVM: fix hvmemul_rep_outs_set_context()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 23.11.17 at 16:09, <JBeulich@xxxxxxxx> wrote:
> There were two issues with this function: Its use of
> hvmemul_do_pio_buffer() was wrong (the function deals only with
> individual port accesses, not repeated ones, i.e. passing it
> "*reps * bytes_per_rep" does not have the intended effect). And it
> could have processed a larger set of operations in one go than was
> probably intended (limited just by the size that xmalloc() can hand
> back).
> 
> By converting to proper use of hvmemul_do_pio_buffer(), no intermediate
> buffer is needed at all. As a result a preemption check is being added.
> 
> Also drop unused parameters from the function.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Ping?

> --- a/xen/arch/x86/hvm/emulate.c
> +++ b/xen/arch/x86/hvm/emulate.c
> @@ -1348,28 +1348,41 @@ static int hvmemul_rep_ins(
>  }
>  
>  static int hvmemul_rep_outs_set_context(
> -    enum x86_segment src_seg,
> -    unsigned long src_offset,
>      uint16_t dst_port,
>      unsigned int bytes_per_rep,
> -    unsigned long *reps,
> -    struct x86_emulate_ctxt *ctxt)
> +    unsigned long *reps)
>  {
> -    unsigned int bytes = *reps * bytes_per_rep;
> -    char *buf;
> -    int rc;
> -
> -    buf = xmalloc_array(char, bytes);
> +    const struct arch_vm_event *ev = current->arch.vm_event;
> +    const uint8_t *ptr;
> +    unsigned int avail;
> +    unsigned long done;
> +    int rc = X86EMUL_OKAY;
>  
> -    if ( buf == NULL )
> +    ASSERT(bytes_per_rep <= 4);
> +    if ( !ev )
>          return X86EMUL_UNHANDLEABLE;
>  
> -    rc = set_context_data(buf, bytes);
> +    ptr = ev->emul.read.data;
> +    avail = ev->emul.read.size;
>  
> -    if ( rc == X86EMUL_OKAY )
> -        rc = hvmemul_do_pio_buffer(dst_port, bytes, IOREQ_WRITE, buf);
> +    for ( done = 0; done < *reps; ++done )
> +    {
> +        unsigned int size = min(bytes_per_rep, avail);
> +        uint32_t data = 0;
> +
> +        if ( done && hypercall_preempt_check() )
> +            break;
> +
> +        memcpy(&data, ptr, size);
> +        avail -= size;
> +        ptr += size;
> +
> +        rc = hvmemul_do_pio_buffer(dst_port, bytes_per_rep, IOREQ_WRITE, 
> &data);
> +        if ( rc != X86EMUL_OKAY )
> +            break;
> +    }
>  
> -    xfree(buf);
> +    *reps = done;
>  
>      return rc;
>  }
> @@ -1391,8 +1404,7 @@ static int hvmemul_rep_outs(
>      int rc;
>  
>      if ( unlikely(hvmemul_ctxt->set_context) )
> -        return hvmemul_rep_outs_set_context(src_seg, src_offset, dst_port,
> -                                            bytes_per_rep, reps, ctxt);
> +        return hvmemul_rep_outs_set_context(dst_port, bytes_per_rep, reps);
>  
>      rc = hvmemul_virtual_to_linear(
>          src_seg, src_offset, bytes_per_rep, reps, hvm_access_read,
> 
> 
> 
> 
> _______________________________________________
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> https://lists.xenproject.org/mailman/listinfo/xen-devel 




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