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Wed, 01 Jun 2022 20:43:59 -0700 (PDT) Received: from localhost ([12.3.194.138]) by smtp.gmail.com with ESMTPSA id g2-20020aa79f02000000b005185407eda5sm2254092pfr.44.2022.06.01.20.43.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Jun 2022 20:43:59 -0700 (PDT) Date: Wed, 01 Jun 2022 20:43:59 -0700 (PDT) X-Google-Original-Date: Wed, 01 Jun 2022 20:40:23 PDT (-0700) Subject: Re: [PATCH v3 00/13] Introduce sv48 support without relocatable kernel In-Reply-To: CC: corbet@lwn.net, Paul Walmsley , aou@eecs.berkeley.edu, zong.li@sifive.com, anup@brainfault.org, Atish.Patra@rivosinc.com, Christoph Hellwig , ryabinin.a.a@gmail.com, glider@google.com, andreyknvl@gmail.com, dvyukov@google.com, ardb@kernel.org, Arnd Bergmann , keescook@chromium.org, guoren@linux.alibaba.com, heinrich.schuchardt@canonical.com, mchitale@ventanamicro.com, panqinglin2020@iscas.ac.cn, linux-doc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-efi@vger.kernel.org, linux-arch@vger.kernel.org From: Palmer Dabbelt To: alexandre.ghiti@canonical.com Message-ID: Mime-Version: 1.0 (MHng) Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 22 Apr 2022 18:50:47 PDT (-0700), Palmer Dabbelt wrote: > On Fri, 01 Apr 2022 05:56:30 PDT (-0700), alexandre.ghiti@canonical.com wrote: >> On Fri, Feb 18, 2022 at 11:45 AM Alexandre Ghiti >> wrote: >>> >>> Hi Palmer, >>> >>> On Thu, Jan 20, 2022 at 11:05 AM Alexandre Ghiti >>> wrote: >>> > >>> > On Thu, Jan 20, 2022 at 8:30 AM Alexandre Ghiti >>> > wrote: >>> > > >>> > > On Thu, Jan 20, 2022 at 5:18 AM Palmer Dabbelt wrote: >>> > > > >>> > > > On Mon, 06 Dec 2021 02:46:44 PST (-0800), alexandre.ghiti@canonical.com wrote: >>> > > > > * Please note notable changes in memory layouts and kasan population * >>> > > > > >>> > > > > This patchset allows to have a single kernel for sv39 and sv48 without >>> > > > > being relocatable. >>> > > > > >>> > > > > The idea comes from Arnd Bergmann who suggested to do the same as x86, >>> > > > > that is mapping the kernel to the end of the address space, which allows >>> > > > > the kernel to be linked at the same address for both sv39 and sv48 and >>> > > > > then does not require to be relocated at runtime. >>> > > > > >>> > > > > This implements sv48 support at runtime. The kernel will try to >>> > > > > boot with 4-level page table and will fallback to 3-level if the HW does not >>> > > > > support it. Folding the 4th level into a 3-level page table has almost no >>> > > > > cost at runtime. >>> > > > > >>> > > > > Note that kasan region had to be moved to the end of the address space >>> > > > > since its location must be known at compile-time and then be valid for >>> > > > > both sv39 and sv48 (and sv57 that is coming). >>> > > > > >>> > > > > Tested on: >>> > > > > - qemu rv64 sv39: OK >>> > > > > - qemu rv64 sv48: OK >>> > > > > - qemu rv64 sv39 + kasan: OK >>> > > > > - qemu rv64 sv48 + kasan: OK >>> > > > > - qemu rv32: OK >>> > > > > >>> > > > > Changes in v3: >>> > > > > - Fix SZ_1T, thanks to Atish >>> > > > > - Fix warning create_pud_mapping, thanks to Atish >>> > > > > - Fix k210 nommu build, thanks to Atish >>> > > > > - Fix wrong rebase as noted by Samuel >>> > > > > - * Downgrade to sv39 is only possible if !KASAN (see commit changelog) * >>> > > > > - * Move KASAN next to the kernel: virtual layouts changed and kasan population * >>> > > > > >>> > > > > Changes in v2: >>> > > > > - Rebase onto for-next >>> > > > > - Fix KASAN >>> > > > > - Fix stack canary >>> > > > > - Get completely rid of MAXPHYSMEM configs >>> > > > > - Add documentation >>> > > > > >>> > > > > Alexandre Ghiti (13): >>> > > > > riscv: Move KASAN mapping next to the kernel mapping >>> > > > > riscv: Split early kasan mapping to prepare sv48 introduction >>> > > > > riscv: Introduce functions to switch pt_ops >>> > > > > riscv: Allow to dynamically define VA_BITS >>> > > > > riscv: Get rid of MAXPHYSMEM configs >>> > > > > asm-generic: Prepare for riscv use of pud_alloc_one and pud_free >>> > > > > riscv: Implement sv48 support >>> > > > > riscv: Use pgtable_l4_enabled to output mmu_type in cpuinfo >>> > > > > riscv: Explicit comment about user virtual address space size >>> > > > > riscv: Improve virtual kernel memory layout dump >>> > > > > Documentation: riscv: Add sv48 description to VM layout >>> > > > > riscv: Initialize thread pointer before calling C functions >>> > > > > riscv: Allow user to downgrade to sv39 when hw supports sv48 if !KASAN >>> > > > > >>> > > > > Documentation/riscv/vm-layout.rst | 48 ++- >>> > > > > arch/riscv/Kconfig | 37 +- >>> > > > > arch/riscv/configs/nommu_k210_defconfig | 1 - >>> > > > > .../riscv/configs/nommu_k210_sdcard_defconfig | 1 - >>> > > > > arch/riscv/configs/nommu_virt_defconfig | 1 - >>> > > > > arch/riscv/include/asm/csr.h | 3 +- >>> > > > > arch/riscv/include/asm/fixmap.h | 1 >>> > > > > arch/riscv/include/asm/kasan.h | 11 +- >>> > > > > arch/riscv/include/asm/page.h | 20 +- >>> > > > > arch/riscv/include/asm/pgalloc.h | 40 ++ >>> > > > > arch/riscv/include/asm/pgtable-64.h | 108 ++++- >>> > > > > arch/riscv/include/asm/pgtable.h | 47 +- >>> > > > > arch/riscv/include/asm/sparsemem.h | 6 +- >>> > > > > arch/riscv/kernel/cpu.c | 23 +- >>> > > > > arch/riscv/kernel/head.S | 4 +- >>> > > > > arch/riscv/mm/context.c | 4 +- >>> > > > > arch/riscv/mm/init.c | 408 ++++++++++++++---- >>> > > > > arch/riscv/mm/kasan_init.c | 250 ++++++++--- >>> > > > > drivers/firmware/efi/libstub/efi-stub.c | 2 >>> > > > > drivers/pci/controller/pci-xgene.c | 2 +- >>> > > > > include/asm-generic/pgalloc.h | 24 +- >>> > > > > include/linux/sizes.h | 1 >>> > > > > 22 files changed, 833 insertions(+), 209 deletions(-) >>> > > > >>> > > > Sorry this took a while. This is on for-next, with a bit of juggling: a >>> > > > handful of trivial fixes for configs that were failing to build/boot and >>> > > > some merge issues. I also pulled out that MAXPHYSMEM fix to the top, so >>> > > > it'd be easier to backport. This is bigger than something I'd normally like to >>> > > > take late in the cycle, but given there's a lot of cleanups, likely some fixes, >>> > > > and it looks like folks have been testing this I'm just going to go with it. >>> > > > >>> > > >>> > > Yes yes yes! That's fantastic news :) >>> > > >>> > > > Let me know if there's any issues with the merge, it was a bit hairy. >>> > > > Probably best to just send along a fixup patch at this point. >>> > > >>> > > I'm going to take a look at that now, and I'll fix anything that comes >>> > > up quickly :) >>> > >>> > I see in for-next that you did not take the following patches: >>> > >>> > riscv: Improve virtual kernel memory layout dump >>> > Documentation: riscv: Add sv48 description to VM layout >>> > riscv: Initialize thread pointer before calling C functions >>> > riscv: Allow user to downgrade to sv39 when hw supports sv48 if !KASAN >>> > >>> > I'm not sure this was your intention. If it was, I believe that at >>> > least the first 2 patches are needed in this series, the 3rd one is a >>> > useful fix and we can discuss the 4th if that's an issue for you. >>> >>> Can you confirm that this was intentional and maybe explain the >>> motivation behind it? Because I see value in those patches. >> >> Palmer, >> >> I read that you were still taking patches for 5.18, so I confirm again >> that the patches above are needed IMO. > > It was too late for this when it was sent (I saw it then, but just got > around to actually doing the work to sort it out). > > It took me a while to figure out exactly what was going on here, but I > think I remember now: that downgrade patch (and the follow-on I just > sent) is broken for medlow, because mm/init.c must be built medany > (which we're using for the mostly-PIC qualities). I remember being in > the middle of rebasing/debugging this a while ago, I must have forgotten > I was in the middle of that and accidentally merged the branch as-is. > Certainly wasn't trying to silently take half the patch set and leave > the rest in limbo, that's the wrong way to do things. > > I'm not sure what the right answer is here, but I just sent a patch to > drop support for medlow. We'll have to talk about that, for now I > cleaned up some other minor issues, rearranged that docs and fix to come > first, and put this at palmer/riscv-sv48. I think that fix is > reasonable to take the doc and fix into fixes, then the dump improvement > on for-next. We'll have to see what folks think about the medany-only > kernels, the other option would be to build FDT as medany which seems a > bit awkward. All but the last one are on for-next, there's some discussion on that last one that pointed out some better ways to do it. > >> Maybe even the relocatable series? > > Do you mind giving me a pointer? I'm not sure why I'm so drop-prone > with your patches, I promise I'm not doing it on purpose. > >> >> Thanks, >> >> Alex >> >>> >>> Thanks, >>> >>> Alex >>> >>> > >>> > I tested for-next on both sv39 and sv48 successfully, I took a glance >>> > at the code and noticed you fixed the PTRS_PER_PGD error, thanks for >>> > that. Otherwise nothing obvious has popped. >>> > >>> > Thanks again, >>> > >>> > Alex >>> > >>> > > >>> > > Thanks! >>> > > >>> > > Alex >>> > > >>> > > > >>> > > > Thanks!