From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ira Weiny Date: Mon, 12 Oct 2020 05:52:19 +0000 Subject: Re: [PATCH RFC PKS/PMEM 57/58] nvdimm/pmem: Stray access protection for pmem->virt_addr Message-Id: <20201012055218.GA2046448@iweiny-DESK2.sc.intel.com> List-Id: References: <20201009195033.3208459-1-ira.weiny@intel.com> <20201009195033.3208459-58-ira.weiny@intel.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: John Hubbard Cc: linux-aio@kvack.org, linux-efi@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, Peter Zijlstra , linux-mmc@vger.kernel.org, Dave Hansen , dri-devel@lists.freedesktop.org, linux-mm@kvack.org, target-devel@vger.kernel.org, linux-mtd@lists.infradead.org, linux-kselftest@vger.kernel.org, samba-technical@lists.samba.org, Thomas Gleixner , drbd-dev@lists.linbit.com, devel@driverdev.osuosl.org, linux-cifs@vger.kernel.org, linux-nilfs@vger.kernel.org, linux-scsi@vger.kernel.org, linux-nvdimm@lists.01.org, linux-rdma@vger.kernel.org, x86@kernel.org, ceph-devel@vger.kernel.org, amd-gfx@lists.freedesktop.org, io-uring@vger.kernel.org, cluster-devel@redhat.com, Ingo Molnar , intel-wired-lan@lists.osuosl.org, xen-devel@lists.xenproject.org, linux-ext4@vger.kernel.org, Fenghua Yu , linux-afs@lists.infradead.org, linux-um@lists.infradead.org, intel-gfx@lists.freedesktop.org, ecryptfs@vger.kernel.org, linux-erofs@lists.ozlabs.org, reiserfs-devel@vger.kernel.org, linux-block@vger.kernel.org, linux-bcache@vger.kernel.org, Borislav Petkov , Andy Lutomirski , Dan Williams , Andrew Morton , linux-cachefs@redhat.com, linux-nfs@vger.kernel.org, linux-ntfs-dev@lists.sourceforge.net, netdev@vger.kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, bpf@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-btrfs@vger.kernel.org On Fri, Oct 09, 2020 at 07:53:07PM -0700, John Hubbard wrote: > On 10/9/20 12:50 PM, ira.weiny@intel.com wrote: > > From: Ira Weiny > > > > The pmem driver uses a cached virtual address to access its memory > > directly. Because the nvdimm driver is well aware of the special > > protections it has mapped memory with, we call dev_access_[en|dis]able() > > around the direct pmem->virt_addr (pmem_addr) usage instead of the > > unnecessary overhead of trying to get a page to kmap. > > > > Signed-off-by: Ira Weiny > > --- > > drivers/nvdimm/pmem.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c > > index fab29b514372..e4dc1ae990fc 100644 > > --- a/drivers/nvdimm/pmem.c > > +++ b/drivers/nvdimm/pmem.c > > @@ -148,7 +148,9 @@ static blk_status_t pmem_do_read(struct pmem_device *pmem, > > if (unlikely(is_bad_pmem(&pmem->bb, sector, len))) > > return BLK_STS_IOERR; > > + dev_access_enable(false); > > rc = read_pmem(page, page_off, pmem_addr, len); > > + dev_access_disable(false); > > Hi Ira! > > The APIs should be tweaked to use a symbol (GLOBAL, PER_THREAD), instead of > true/false. Try reading the above and you'll see that it sounds like it's > doing the opposite of what it is ("enable_this(false)" sounds like a clumsy > API design to *disable*, right?). And there is no hint about the scope. Sounds reasonable. > > And it *could* be so much more readable like this: > > dev_access_enable(DEV_ACCESS_THIS_THREAD); I'll think about the flag name. I'm not liking 'this thread'. Maybe DEV_ACCESS_[GLOBAL|THREAD] Ira