linux-kernel - Re: [PATCH v14 13/17] IB/mlx4, arm64: untag user pointers in mlx4_get_umem

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Date:   Mon, 6 May 2019 18:21:56 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-rdma@...r.kernel.org, linux-media@...r.kernel.org,
        kvm@...r.kernel.org,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...omium.org>,
        Yishai Hadas <yishaih@...lanox.com>, Kuehling@...gle.com,
        Felix <Felix.Kuehling@....com>, Deucher@...gle.com,
        Alexander <Alexander.Deucher@....com>, Koenig@...gle.com,
        Christian <Christian.Koenig@....com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Jens Wiklander <jens.wiklander@...aro.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Leon Romanovsky <leon@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Evgeniy Stepanov <eugenis@...gle.com>,
        Lee Smith <Lee.Smith@....com>,
        Ramana Radhakrishnan <Ramana.Radhakrishnan@....com>,
        Jacob Bramley <Jacob.Bramley@....com>,
        Ruben Ayrapetyan <Ruben.Ayrapetyan@....com>,
        Robin Murphy <robin.murphy@....com>,
        Chintan Pandya <cpandya@...eaurora.org>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Dave Martin <Dave.Martin@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Szabolcs Nagy <Szabolcs.Nagy@....com>,
        Leon Romanovsky <leonro@...lanox.com>
Subject: Re: [PATCH v14 13/17] IB/mlx4, arm64: untag user pointers in mlx4_get_umem_mr

On Fri, May 3, 2019 at 7:03 PM Catalin Marinas <catalin.marinas@....com> wrote:
>
> On Tue, Apr 30, 2019 at 03:25:09PM +0200, Andrey Konovalov wrote:
> > This patch is a part of a series that extends arm64 kernel ABI to allow to
> > pass tagged user pointers (with the top byte set to something else other
> > than 0x00) as syscall arguments.
> >
> > mlx4_get_umem_mr() uses provided user pointers for vma lookups, which can
> > only by done with untagged pointers.
> >
> > Untag user pointers in this function.
> >
> > Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> > Reviewed-by: Leon Romanovsky <leonro@...lanox.com>
> > ---
> >  drivers/infiniband/hw/mlx4/mr.c | 7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/infiniband/hw/mlx4/mr.c b/drivers/infiniband/hw/mlx4/mr.c
> > index 395379a480cb..9a35ed2c6a6f 100644
> > --- a/drivers/infiniband/hw/mlx4/mr.c
> > +++ b/drivers/infiniband/hw/mlx4/mr.c
> > @@ -378,6 +378,7 @@ static struct ib_umem *mlx4_get_umem_mr(struct ib_udata *udata, u64 start,
> >        * again
> >        */
> >       if (!ib_access_writable(access_flags)) {
> > +             unsigned long untagged_start = untagged_addr(start);
> >               struct vm_area_struct *vma;
> >
> >               down_read(&current->mm->mmap_sem);
> > @@ -386,9 +387,9 @@ static struct ib_umem *mlx4_get_umem_mr(struct ib_udata *udata, u64 start,
> >                * cover the memory, but for now it requires a single vma to
> >                * entirely cover the MR to support RO mappings.
> >                */
> > -             vma = find_vma(current->mm, start);
> > -             if (vma && vma->vm_end >= start + length &&
> > -                 vma->vm_start <= start) {
> > +             vma = find_vma(current->mm, untagged_start);
> > +             if (vma && vma->vm_end >= untagged_start + length &&
> > +                 vma->vm_start <= untagged_start) {
> >                       if (vma->vm_flags & VM_WRITE)
> >                               access_flags |= IB_ACCESS_LOCAL_WRITE;
> >               } else {
>
> Discussion ongoing on the previous version of the patch but I'm more
> inclined to do this in ib_uverbs_(re)reg_mr() on cmd.start.

OK, I want to publish v15 sooner to fix the issue with emails
addresses, so I'll implement this approach there for now.



>
> --
> Catalin