> -----Original Message----- > From: Roger Pau Monne <[email protected]> > Sent: 09 September 2020 15:51 > To: [email protected] > Cc: Roger Pau Monne <[email protected]>; Jan Beulich <[email protected]>; > Andrew Cooper > <[email protected]>; Wei Liu <[email protected]>; Paul Durrant > <[email protected]> > Subject: [PATCH] x86/hvm: don't treat MMIO pages as special ones regarding > cache attributes > > MMIO regions below the maximum address on the memory map can have a > backing page struct that's shared with dom_io (see x86 > arch_init_memory and it's usage of share_xen_page_with_guest), and > thus also fulfill the is_special_page check because the page has the > Xen heap bit set. > > This is incorrect for MMIO regions when is_special_page is used by > epte_get_entry_emt, as it will force direct MMIO regions mapped into > the guest p2m to have the cache attributes set to write-back. > > Add an extra check in epte_get_entry_emt in order to detect pages > shared with dom_io (ie: MMIO regions) and don't force them to > write-back cache type on that case. > > Fixes: 81fd0d3ca4b2cd ('x86/hvm: simplify 'mmio_direct' check in > epte_get_entry_emt()') > Signed-off-by: Roger Pau Monné <[email protected]> > --- > Cc: Paul Durrant <[email protected]>
This looks like the right thing to do... Reviewed-by: Paul Durrant <[email protected]>
