Re: [Xen-devel] [PATCH 1/3] x86/HVM: __hvm_copy() should not write to p2m_ioreq_server pages

[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 1/3] x86/HVM: __hvm_copy() should not write to
> p2m_ioreq_server pages
> 
> Commit 3bdec530a5 ("x86/HVM: split page straddling emulated accesses in
> more cases") introduced a hvm_copy_to_guest_linear() attempt before
> falling back to hvmemul_linear_mmio_write(). This is wrong for the
> p2m_ioreq_server special case. That change widened a pre-existing issue
> though: Other writes to such pages also need to be failed (or forced
> through emulation), in particular hypercall buffer writes.
> 
> Reported-by: ??? <???@citrix.com>

I think this should be: Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>

> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

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

> 
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -3202,6 +3202,12 @@ static enum hvm_translation_result __hvm
>          if ( res != HVMTRANS_okay )
>              return res;
> 
> +        if ( (flags & HVMCOPY_to_guest) && p2mt == p2m_ioreq_server )
> +        {
> +            put_page(page);
> +            return HVMTRANS_bad_gfn_to_mfn;
> +        }
> +
>          p = (char *)__map_domain_page(page) + (addr & ~PAGE_MASK);
> 
>          if ( flags & HVMCOPY_to_guest )
> 


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