[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Balloon driver bug in increase_reservation
On Mon, 2013-09-02 at 15:43 +0100, Wei Liu wrote: > Hi, Stefano > > I found another bug in the balloon scratch page code. As I didn't follow > the discussion on scratch page so I cannot propose a proper fix at the > moment. > > The problem is that in balloon.c:increase_reservation, when a ballooned > page is resued, it can have a valid P2M entry pointing to the scratch, > hitting the BUG_ON > > BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) && > phys_to_machine_mapping_valid(pfn)); > > As balloon worker might run by a CPU other then the one that returns the > page, checking pfn_to_mfn(pfn) == local_cpu_scratch_page_mfn wouldn't > work. Checking pfn_to_mfn(pfn) belongs to the set of all scratch page > mfns is not desirable. This makes me think that whoever suggested that pfn_to_mfn for a ballooned page out to return INVALID_MFN was right. Even though we happen to have put a mapping there there pages are "logically empty" and that's really what callers such as phys_to_machine_mapping_valid care about, not whether the processor thinks there is a mapping or not. > > My thoughts so far: > 1. remove that BUG_ON (looks like a wrong fix though) > 2. make balloon scratch page global > > Other thoughts? > > Wei. > > _______________________________________________ > Xen-devel mailing list > Xen-devel@xxxxxxxxxxxxx > http://lists.xen.org/xen-devel _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
|
Lists.xenproject.org is hosted with RackSpace, monitoring our |