On Mon, 6 Mar 2023 at 21:24, Richard Henderson <richard.hender...@linaro.org> wrote: > > On 3/6/23 04:56, Peter Maydell wrote: > > On Mon, 6 Mar 2023 at 02:14, Richard Henderson > > <richard.hender...@linaro.org> wrote: > >> > >> Zero is the value for 'off', and should not be used with -R. > >> We have been enforcing host page alignment for the non-R > >> fallback of MAX_RESERVED_VA, but failing to enforce for -R. > > > > I'm pretty sure we have users who specifically use "-R 0" to > > ask for "definitely turn off any reserved VA". > > Here's a random example from an old gcc bug report: > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60681 > > and somebody using it via the environment variable: > > https://www.openembedded.org/pipermail/openembedded-core/2015-January/100572.html > > Odd. > > Well, it won't actually have the effect of "definitely turn off", it will > merely leave > things as per the default, which *will* enable reserved va for 32-bit guests > on 64-bit hosts. > > The only remaining question is whether we diagnose this oddness or silently > accept it. It > feels like someone playing with options they don't actually understand and an > error is > warranted.
I'm pretty sure I've issued the advice "turn off the reserved area stuff with -R 0" in the past, for working around various QEMU bugs where it wasn't able to allocate the whole reserved area it wanted to but the guest program didn't actually care. thanks -- PMM
