On 20.10.20 21:17, Peter Xu wrote: > On Thu, Sep 24, 2020 at 06:04:21PM +0200, David Hildenbrand wrote: >> We want to separate the two cases whereby >> - balloning drivers do random discards on random guest memory (e.g., >> virtio-balloon) - uncoordinated discards >> - paravirtualized memory devices do discards in well-known granularity, >> and always know which block is currently accessible or inaccessible by >> a guest. - coordinated discards >> >> This will be required to get virtio_mem + vfio running - vfio still >> wants to block random memory ballooning. >> >> Cc: Paolo Bonzini <pbonz...@redhat.com> >> Cc: "Michael S. Tsirkin" <m...@redhat.com> >> Cc: Alex Williamson <alex.william...@redhat.com> >> Cc: Wei Yang <richardw.y...@linux.intel.com> >> Cc: Dr. David Alan Gilbert <dgilb...@redhat.com> >> Cc: Igor Mammedov <imamm...@redhat.com> >> Cc: Pankaj Gupta <pankaj.gupta.li...@gmail.com> >> Cc: Peter Xu <pet...@redhat.com> >> Signed-off-by: David Hildenbrand <da...@redhat.com> >> --- >> exec.c | 109 ++++++++++++++++++++++++++++++++++-------- >> include/exec/memory.h | 36 ++++++++++++-- >> 2 files changed, 121 insertions(+), 24 deletions(-) >> >> diff --git a/exec.c b/exec.c >> index e34b602bdf..83098e9230 100644 >> --- a/exec.c >> +++ b/exec.c >> @@ -4098,52 +4098,121 @@ void mtree_print_dispatch(AddressSpaceDispatch *d, >> MemoryRegion *root) >> * If positive, discarding RAM is disabled. If negative, discarding RAM is >> * required to work and cannot be disabled. >> */ >> -static int ram_block_discard_disabled; >> +static int uncoordinated_discard_disabled; >> +static int coordinated_discard_disabled; > > Instead of duplicating the codes, how about start to make it an array? > > Btw, iiuc these flags do not need atomic operations at all, because all > callers > should be with BQL and called majorly during machine start/reset. Even not, I > think we can also use a mutex, maybe it could make things simpler. No strong > opinion, though. >
I remember there were some !BQL users (but I might be confusing it with postcopy code that once used to inhibit the balloon without BQL). Will double-check. Simplifying it is certainly a good idea. (we want to be able to check from virtio-balloon code repeatedly without taking a mutex over and over again :) ) Thanks! -- Thanks, David / dhildenb
