On Mon, May 23, 2022 at 03:42:49PM +0100, Andre Przywara wrote: > On Fri, 20 May 2022 21:51:07 +0100 > Will Deacon <will@xxxxxxxxxx> wrote: > > Hi, > > > On Fri, 20 May 2022 14:37:04 +0000, Keir Fraser wrote: > > > While playing with kvmtool's virtio_balloon device I found a couple of > > > niggling issues with the printing of memory stats. Please consider > > > these fairly trivial fixes. > > Unfortunately patch 2/2 breaks compilation on userland with older kernel > headers, like Ubuntu 18.04: > ... > CC builtin-stat.o > builtin-stat.c: In function 'do_memstat': > builtin-stat.c:86:8: error: 'VIRTIO_BALLOON_S_HTLB_PGALLOC' undeclared (first use in this function); did you mean 'VIRTIO_BALLOON_S_AVAIL'? > case VIRTIO_BALLOON_S_HTLB_PGALLOC: > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > VIRTIO_BALLOON_S_AVAIL > (repeated for VIRTIO_BALLOON_S_HTLB_PGFAIL and VIRTIO_BALLOON_S_CACHES). > > I don't quite remember what we did here in the past in those cases, > conditionally redefine the symbols in a local header, or protect the > new code with an #ifdef? For what it's worth, my opinion is that the sensible options are to: 1. Build against the latest stable, or a specified version of, kernel headers; or 2. Protect with ifdef'ery until new definitions are considered "common enough". Supporting older headers by grafting or even modifying required newer definitions on top seems a horrid middle ground, albeit I can appreciate the pragmatism of it. Regards, Keir > I would lean towards the former (and hacking this in works), but then we > would need to redefine VIRTIO_BALLOON_S_NR, to encompass the new symbols, > which sounds fragile. > > Happy to send a patch if we agree on an approach. > > Cheers, > Andre > > > > > > > Keir Fraser (2): > > > virtio/balloon: Fix a crash when collecting stats > > > stat: Add descriptions for new virtio_balloon stat types > > > > > > [...] > > > > Applied to kvmtool (master), thanks! > > > > [1/2] virtio/balloon: Fix a crash when collecting stats > > https://git.kernel.org/will/kvmtool/c/3a13530ae99a > > [2/2] stat: Add descriptions for new virtio_balloon stat types > > https://git.kernel.org/will/kvmtool/c/bc77bf49df6e > > > > Cheers, >
