Re: [Qemu-devel] [RFC PATCH v4 02/20] memattrs: add debug attribute

[Stefan Hajnoczi]

On Wed, Mar 08, 2017 at 03:51:28PM -0500, Brijesh Singh wrote:
> Add a new debug attribute, the attribute should be set when guest memory
> accesses are performed for debug purposes.
> The attribute will be used in SEV guest, where we need to distinguish normal
> vs debug access to guest memory. In debug mode, we need to use SEV commands
> to access the guest memory.
> 
> Signed-off-by: Brijesh Singh <address@hidden>
> ---
>  include/exec/memattrs.h |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/include/exec/memattrs.h b/include/exec/memattrs.h
> index e601061..b802073 100644
> --- a/include/exec/memattrs.h
> +++ b/include/exec/memattrs.h
> @@ -37,6 +37,8 @@ typedef struct MemTxAttrs {
>      unsigned int user:1;
>      /* Requester ID (for MSI for example) */
>      unsigned int requester_id:16;
> +    /* Memory access for debug purposes */

What does "debug purposes" mean?  gdbstub?  Can the guest initiate debug
memory accesses or is the purely QEMU-internal?

> +    unsigned int debug:1;
>  } MemTxAttrs;
>  
>  /* Bus masters which don't specify any attributes will get this,
> @@ -46,4 +48,6 @@ typedef struct MemTxAttrs {
>   */
>  #define MEMTXATTRS_UNSPECIFIED ((MemTxAttrs) { .unspecified = 1 })
>  
> +/* Access the guest memory for debug purposes */
> +#define MEMTXATTRS_DEBUG ((MemTxAttrs) { .debug = 1 })
>  #endif
> 
>

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