Re: [Xen-devel] [PATCH 2/3] x86/HVM: make hvmemul_map_linear_addr() honor p2m_ioreq_server

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: 13 November 2018 10:14
> To: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
> Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; Paul Durrant
> <Paul.Durrant@xxxxxxxxxx>; Wei Liu <wei.liu2@xxxxxxxxxx>
> Subject: [PATCH 2/3] x86/HVM: make hvmemul_map_linear_addr() honor
> p2m_ioreq_server
> 
> Write accesses to p2m_ioreq_server pages should get redirected to the
> emulator also when using the mapping approach. Extend the
> p2m_is_discard_write() check there, and restrict both to the write
> access case (this is just a latent bug as currently we go this route
> only for write accesses).
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

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

> 
> --- a/xen/arch/x86/hvm/emulate.c
> +++ b/xen/arch/x86/hvm/emulate.c
> @@ -613,10 +613,21 @@ static void *hvmemul_map_linear_addr(
> 
>          *mfn++ = page_to_mfn(page);
> 
> -        if ( p2m_is_discard_write(p2mt) )
> +        if ( pfec & PFEC_write_access )
>          {
> -            err = ERR_PTR(~X86EMUL_OKAY);
> -            goto out;
> +            if ( p2m_is_discard_write(p2mt) )
> +            {
> +                err = ERR_PTR(~X86EMUL_OKAY);
> +                goto out;
> +            }
> +
> +            if ( p2mt == p2m_ioreq_server )
> +            {
> +                err = NULL;
> +                goto out;
> +            }
> +
> +            ASSERT(p2mt == p2m_ram_logdirty || !p2m_is_readonly(p2mt));
>          }
>      }
> 
> 
> 
> 


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