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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Wed, 11 May 2016 22:07:27 +0200
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Subject: Re: [Qemu-devel] [PATCH v7 2/2] Add optionrom compatible with
 fw_cfg DMA version
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To: "Richard W.M. Jones" <rjones@redhat.com>, qemu-devel@nongnu.org
Cc: stefanha@gmail.com, marc.mari.barcelo@gmail.com, ehabkost@redhat.com, mst@redhat.com, kraxel@redhat.com, rth@twiddle.net, lersek@redhat.com



On 11/05/2016 19:42, Richard W.M. Jones wrote:
> +
> +#ifdef __clang__
> +#define ADDR32
> +#else
> +#define ADDR32 "addr32 "
> +#endif
> +
> +static inline uint16_t readw_es(uint16_t offset)
> +{
> +    uint16_t val;
> +    asm(ADDR32"movw %%es:(%1), %0" : "=r"(val) : "r"((uint32_t)offset));
> +    barrier();
> +    return val;
> +}

Please check that the output is the same byte-by-byte for this asm.

I guess this is okay if we have a guarantee from clang that the asm
block stays at the beginning.  Perhaps check for the 0x55 0xaa signature
in signrom.py?

Thanks,

Paolo