From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Hubbard Date: Sat, 10 Oct 2020 02:53:07 +0000 Subject: Re: [PATCH RFC PKS/PMEM 57/58] nvdimm/pmem: Stray access protection for pmem->virt_addr Message-Id: List-Id: References: <20201009195033.3208459-1-ira.weiny@intel.com> <20201009195033.3208459-58-ira.weiny@intel.com> In-Reply-To: <20201009195033.3208459-58-ira.weiny@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ira.weiny@intel.com, Andrew Morton , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Andy Lutomirski , Peter Zijlstra Cc: linux-aio@kvack.org, linux-efi@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, 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, ceph-devel@vger.kernel.org, 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, amd-gfx@lists.freedesktop.org, linux-afs@lists.infradead.org, cluster-devel@redhat.com, linux-cachefs@redhat.com, intel-wired-lan@lists.osuosl.org, xen-devel@lists.xenproject.org, linux-ext4@vger.kernel.org, Fenghua Yu , 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, Dan Williams , io-uring@vger.kernel.org, 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 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. And it *could* be so much more readable like this: dev_access_enable(DEV_ACCESS_THIS_THREAD); thanks, -- John Hubbard NVIDIA