On Mon 20-08-18 07:20:27, Andi Kleen wrote: > On Mon, Aug 20, 2018 at 11:58:35AM +0200, Vlastimil Babka wrote: > > On 32bit PAE kernels on 64bit hardware with enough physical bits, > > l1tf_pfn_limit() will overflow unsigned long. This in turn affects > > max_swapfile_size() and can lead to swapon returning -EINVAL. This has been > > observed in a 32bit guest with 42 bits physical address size, where > > max_swapfile_size() overflows exactly to 1 << 32, thus zero, and produces the > > following warning to dmesg: > > > > [ 6.396845] Truncating oversized swap area, only using 0k out of 2047996k > > > > Fix this by using unsigned long long instead. > > Looks good. > > Acked-by: Andi Kleen <ak@xxxxxxxxxxxxxxx> > > BTW our much worse problems right now are crash reports on several > stable kernels, especially with large pages Do you have any reference? > I'll dig into this more today, but if you have any hints from testing/fixing > your own backports please share them. Well, we have seen some issues on pre 3.12 kernels due to misbackporting prot_none mitigations. PMD format is different in pre 4.4 kernels. Maybe this is a similar issue. -- Michal Hocko SUSE Labs
