Re: [PATCH] tools/libs/ctrl: add and export xc_memory_op

[Juergen Gross <jgross@xxxxxxxx>]

On 19.05.22 15:59, Lengyel, Tamas wrote:
> > -----Original Message-----
> > From: Xen-devel <xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf Of
> > Juergen Gross
> > Sent: Thursday, May 19, 2022 9:33 AM
> > To: Lengyel, Tamas <tamas.lengyel@xxxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx
> > Cc: Wei Liu <wl@xxxxxxx>; Anthony PERARD <anthony.perard@xxxxxxxxxx>;
> > Cooper, Andrew <andrew.cooper3@xxxxxxxxxx>
> > Subject: Re: [PATCH] tools/libs/ctrl: add and export xc_memory_op
> >
> > On 19.05.22 15:27, Tamas K Lengyel wrote:
> > > Add and export xc_memory_op so that do_memory_op can be used by tools
> > > linking with libxc. This is effectively in the same spirit as the
> > > existing xc_domctl and xc_sysctl functions, which are already exported.
> > >
> > > In this patch we move do_memory_op into xc_private.h as a static
> > > inline function and convert its 'cmd' input from int to unsigned int
> > > to accurately reflect what the hypervisor expects. No other changes are made
> > to the function.
> > > Signed-off-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxx>
> > > ---
> > >    tools/include/xenctrl.h      |  1 +
> > >    tools/libs/ctrl/xc_private.c | 63 +++---------------------------------
> > >    tools/libs/ctrl/xc_private.h | 58 ++++++++++++++++++++++++++++++++-
> > >    3 files changed, 63 insertions(+), 59 deletions(-)
> > >
> > > diff --git a/tools/include/xenctrl.h b/tools/include/xenctrl.h index
> > > 95bd5eca67..484e354412 100644
> > > --- a/tools/include/xenctrl.h
> > > +++ b/tools/include/xenctrl.h
> > > @@ -1597,6 +1597,7 @@ int xc_vmtrace_set_option(xc_interface *xch,
> > > uint32_t domid,
> > >
> > >    int xc_domctl(xc_interface *xch, struct xen_domctl *domctl);
> > >    int xc_sysctl(xc_interface *xch, struct xen_sysctl *sysctl);
> > > +long xc_memory_op(xc_interface *xch, unsigned int cmd, void *arg,
> > > +size_t len);
> > >
> > >    int xc_version(xc_interface *xch, int cmd, void *arg);
> > >
> > > diff --git a/tools/libs/ctrl/xc_private.c
> > > b/tools/libs/ctrl/xc_private.c index c0422662f0..6a247d2b1f 100644
> > > --- a/tools/libs/ctrl/xc_private.c
> > > +++ b/tools/libs/ctrl/xc_private.c
> > > @@ -326,64 +326,6 @@ int xc_flush_mmu_updates(xc_interface *xch, struct
> > xc_mmu *mmu)
> > >        return flush_mmu_updates(xch, mmu);
> > >    }
> > >
> > > -long do_memory_op(xc_interface *xch, int cmd, void *arg, size_t len)
> > Why don't you just rename this function and modify the users to use the new
> > name?
> For two reasons:
> 1) having the do_memory_op as a static inline is consistent with how do_domctl 
> and do_sysctl are implemented, so logically that's what I would expect to see 
> for the memory_op hypercall as well.
It is much more complicated than the do_domctl and do_sysctl inlines.

Additionally it is being used by libxenguest, so making it an inline would
expose lots of libxenctrl internals to libxenguest.

> 2) the patch itself is cleaner because there is no churn in all the files that 
> previously called do_memory_op.
OTOH all callers are in Xen, so its no deal to change those.


Juergen

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