Re: [Xen-devel] [PATCH v2 4/4] x86/hvm: Implement hvmemul_write() using real mappings

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 08/09/17 17:05, Alexandru Isaila wrote:
> +    } while ( frame < final );
> +
> +    /* Entire access within a single frame? */
> +    if ( first == final )
> +        mapping = map_domain_page(hvmemul_ctxt->mfn[0]) + (linear & 
> ~PAGE_MASK);
> +    /* Multiple frames? Need to vmap(). */
> +    else if ( (mapping = vmap(hvmemul_ctxt->mfn,
> +                              mfn - hvmemul_ctxt->mfn)) == NULL )
> +        goto unhandleable;
> +
> +#ifndef NDEBUG /* Poision unused mfn[]s with INVALID_MFN. */
> +    while ( mfn < hvmemul_ctxt->mfn + ARRAY_SIZE(hvmemul_ctxt->mfn) )
> +    {
> +        ASSERT(mfn_x(*mfn) == 0);
> +        *mfn++ = INVALID_MFN;
> +    }
> +#endif
> +
> +    return mapping;

/sigh - its sad what you notice when looking over your own code somewhat
later...

the + (linear & ~PAGE_MASK) needs removing from the map_domain_page()
call, and adding to this return statement, because it also needs to
happen for the vmap() case.

~Andrew

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