On 13/11/18 10:13, Jan Beulich wrote:
> 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>
> Signed-off-by: Jan Beulich <jbeul...@suse.com>
>
> --- 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 )
While this does address the issue, I'm concerned about hardcoding the
behaviour here.
p2m_ioreq_server doesn't mean "I want shadowing properties". It has an
as-yet unspecified per-ioreq-client meaning.
We either want to rename p2m_ioreq_server to something which indicates
its "allow-reads/emulate writes" behaviour, or design a way for the
ioreq client to specify the behaviour it wants.
~Andrew
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
