On Thu, Sep 01, 2016 at 02:39:37PM -0300, Eduardo Habkost wrote: > On Thu, Sep 01, 2016 at 05:41:52PM +0200, Paolo Bonzini wrote: > > On 01/09/2016 17:10, Eduardo Habkost wrote: > > > Ouch. It looks like the ordering requirements are messier than I > > > thought. vhost-user depends on the memory backends to be already > > > initialized. > > > > You could also look at delaying initialization of vhost-user, not > > sending anything on the wire until after machine creation. > > I was wishing the bug could be fixed without the need to touch > vhost, but I will take a look. > > BTW, the vhost error is actually happening inside a VCPU thread, > after everything was supposed to be fully initialized. Maybe the > memory listener logic in vhost.c is broken somehow?
This is getting hairier. Summary: 1) vhost_user_set_mem_table() fails because dev->mem->nregions is 0 2) dev->mem->nregions is supposed to get new entries based on the memory listener callbacks 3) vhost_region_add() gets called properly, and calls vhost_set_memory(), but: 4) vhost_set_memory() forces add=false if memory_region_get_dirty_log_mask(section->mr) & ~(1 << DIRTY_MEMORY_MIGRATION) (I have no idea why) 5) memory_region_init_ram_from_file() sets: mr->dirty_log_mask = tcg_enabled() ? (1 << DIRTY_MEMORY_CODE) : 0; (I don't understand what are the consequences of this) 6) The tcg_enabled() check above is broken if the memory region is created before configure_accelerator() is called. My patch moves memory backend initialization after configure_accelerator() I'm very confused. My patch seems to fix the dirty_log_mask initialization at (5) by accident? But for some reason this breaks vhost-user and makes it ignore all memory regions if using TCG? (vhost-user-test forces accel=tcg, BTW) As I have no idea why vhost_set_memory() ignores the memory region based on memory_region_get_dirty_log_mask(), I don't know what's supposed to be happening here. Any help would be appreciated. -- Eduardo
