On Wed, Sep 9, 2020 at 2:23 PM Peter Maydell <[email protected]> wrote: > On Wed, 9 Sep 2020 at 10:12, Stefan Hajnoczi <[email protected]> wrote: > > On Thu, Sep 03, 2020 at 01:08:19PM +0200, Philippe Mathieu-Daudé wrote: > > > The main patch is: > > > "exec/memattrs: Introduce MemTxAttrs::direct_access field". > > > This way we can restrict accesses to ROM/RAM by setting the > > > 'direct_access' field. Illegal accesses return MEMTX_BUS_ERROR. > > > > QEMU needs to simulate the behavior of real hardware. What is the > > behavior of real hardware? > > It varies, depending on the hardware. The most common thing > is probably "happens to work by luck", which is OK for hardware > but doesn't help us much since our software implementation is > naturally more serialized than hardware is and since we don't > want to allow guests to make QEMU crash or misbehave.
The memory API bounce buffer mechanism is evidence that some board(s) need or needed it. At a minimum we need to find out the reason for the bounce buffer mechanism to avoid breaking guests. Stefan
