Re: [Qemu-devel] [PATCH 0/5] linux-user: Support signal passing for targets having more signals than host

[Aleksandar Markovic]

On May 23, 2019 3:46 PM, "Peter Maydell" <address@hidden> wrote:
>
> On Wed, 22 May 2019 at 19:57, Aleksandar Markovic
> <address@hidden> wrote:
> >
> > From: Aleksandar Markovic <address@hidden>
> >
> > Most of the targets (including Intel) define 64 signals. This
> > creates difficulties for targets that define, for example, 128
> > signals. This series adds support for signal passing even if
> > the host defines less signals than the target.
>
> Could you elaborate a bit on how much functionality
> is provided for signal numbers which the target has
> but the host does not? For instance, it seems likely
> that attempts by the guest to kill(other_pid, sig) will
> fail if sig is not in the supported-by-the-target range.
> But is it possible for the guest process to deliver
> one of these signals to itself ?
>
> This patchset is interesting because in fact pretty much
> every target supports more signals than our host code
> can provide, because the host libc steals several
> signals for its own purposes and QEMU can't use them.
> Being able to multiplex several guest signals onto
> one host signal might let us run some guest binaries
> we currently can't handle correctly.
>

Hello, Peter.

I would ask the author, Milos Stojanovic, to provide us with details you
asked for.

I am here just the integrator and the submitter, and even though I could
perhaps answer your questions accurately, I would prefer Milos as the main
person to talk to.

I would like to add that this series is already in exploation here in Wave,
for some internal projects involving QEMU. People are happy with it, it
solved some long-standing problems, and there is no known open issue
related to this code.

The solution has its own limitations, as is spelled out in commit messages,
just to keep your expectations realistic, but overall I find it incredibly
useful, and very good, given the complex problem it tackles.

I would like now to pass the “floor” to Milos.

Yours,
Aleksandar

> thanks
> -- PMM
>