Before adding a new vCPU operation to register the runstate area by guest-physical address, add code to actually keep such areas up-to-date.
Signed-off-by: Jan Beulich <[email protected]> --- RFC: Pages aren't marked dirty when written to (matching the handling of space mapped by map_vcpu_info() afaict), on the basis that the registrations are lost anyway across migration. Plus the contents of the areas in question have to be deemed volatile in the first place (so saving a "most recent" value is pretty meaningless even for e.g. snapshotting). RFC: Can we perhaps avoid the VM-assist conditionals, assuming the more modern behavior to apply uniformly for gaddr-based registrations? RFC: HVM guests (on x86) can change bitness and hence layout (and size! and alignment) of the runstate area. I don't think it is an option to require 32-bit code to pass a range such that even the 64-bit layout wouldn't cross a page boundary (and be suitably aligned). I also don't see any other good solution, so for now a crude approach with an extra boolean is used (using has_32bit_shinfo() isn't race free and could hence lead to overrunning the mapped space). --- a/xen/common/domain.c +++ b/xen/common/domain.c @@ -1599,14 +1599,55 @@ bool update_runstate_area(struct vcpu *v struct guest_memory_policy policy = { }; void __user *guest_handle = NULL; struct vcpu_runstate_info runstate; + struct vcpu_runstate_info *map = v->runstate_guest_area.map; + + memcpy(&runstate, &v->runstate, sizeof(runstate)); + + if ( map ) + { + uint64_t *pset = NULL; +#ifdef CONFIG_COMPAT + struct compat_vcpu_runstate_info *cmap = NULL; + + if ( v->runstate_guest_area_compat ) + cmap = (void *)map; +#endif + + if ( VM_ASSIST(v->domain, runstate_update_flag) ) + { +#ifdef CONFIG_COMPAT + if ( cmap ) + pset = &cmap->state_entry_time; + else +#endif + pset = &map->state_entry_time; + runstate.state_entry_time |= XEN_RUNSTATE_UPDATE; + write_atomic(pset, runstate.state_entry_time); + smp_wmb(); + } + +#ifdef CONFIG_COMPAT + if ( cmap ) + XLAT_vcpu_runstate_info(cmap, &runstate); + else +#endif + *map = runstate; + + if ( pset ) + { + smp_wmb(); + runstate.state_entry_time &= ~XEN_RUNSTATE_UPDATE; + write_atomic(pset, runstate.state_entry_time); + } + + return true; + } if ( guest_handle_is_null(runstate_guest(v)) ) return true; update_guest_memory_policy(v, &policy); - memcpy(&runstate, &v->runstate, sizeof(runstate)); - if ( VM_ASSIST(v->domain, runstate_update_flag) ) { #ifdef CONFIG_COMPAT --- a/xen/include/xen/sched.h +++ b/xen/include/xen/sched.h @@ -231,6 +231,8 @@ struct vcpu #ifdef CONFIG_COMPAT /* A hypercall is using the compat ABI? */ bool hcall_compat; + /* Physical runstate area registered via compat ABI? */ + bool runstate_guest_area_compat; #endif #ifdef CONFIG_IOREQ_SERVER
