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X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230517_074222_530257_377047EF X-CRM114-Status: GOOD ( 63.88 ) X-Mailman-Approved-At: Wed, 17 May 2023 08:06:26 -0700 X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org Sorry, pressed "reply" instead of "reply all"... ---------- Forwarded message --------- From: Alexandre Ghiti Date: Wed, May 17, 2023 at 4:40 PM Subject: Re: Bug report: kernel paniced when system hibernates To: Song Shuai , Anup Patel , Atish Kumar Patra On Wed, May 17, 2023 at 1:05 PM Song Shuai wrote: > > Alexandre Ghiti 于2023年5月17日周三 08:58写道： > > > > On Tue, May 16, 2023 at 1:12 PM Alexandre Ghiti wrote: > > > > > > Hi Song, > > > > > > On Tue, May 16, 2023 at 11:24 AM Song Shuai wrote: > > > > > > > > Description of problem: > > > > > > > > The latest hibernation support[1] of RISC-V Linux produced a kernel panic. > > > > The entire log has been posted at this link: https://termbin.com/sphl . > > > > > > > > How reproducible: > > > > > > > > You can reproduce it with the following step : > > > > > > > > 1. prepare the environment with > > > > - Qemu-virt v8.0.0 (with OpenSbi v1.2) > > > > - Linux v6.4-rc1 > > > > > > > > 2. start the Qemu virt > > > > ```sh > > > > $ cat ~/8_riscv/start_latest.sh > > > > #!/bin/bash > > > > /home/song/8_riscv/3_acpi/qemu/ooo/usr/local/bin/qemu-system-riscv64 \ > > > > -smp 2 -m 4G -nographic -machine virt \ > > > > -kernel /home/song/9_linux/linux/00_rv_test/arch/riscv/boot/Image \ > > > > -append "root=/dev/vda ro eaylycon=uart8250,mmio,0x10000000 > > > > early_ioremap_debug console=ttyS0 loglevel=8 memblock=debug > > > > no_console_suspend audit=0 3" \ > > > > -drive file=/home/song/8_riscv/fedora/stage4-disk.img,format=raw,id=hd0 \ > > > > -device virtio-blk-device,drive=hd0 \ > > > > -drive file=/home/song/8_riscv/fedora/adisk.qcow2,format=qcow2,id=hd1 \ > > > > -device virtio-blk-device,drive=hd1 \ > > > > -gdb tcp::1236 #-S > > > > ``` > > > > 3. execute hibernation > > > > > > > > ```sh > > > > swapon /dev/vdb2 # this is my swap disk > > > > > > > > echo disk > /sys/power/state > > > > ``` > > > > > > > > 4. Then you will encounter the kernel panic logged in the above link > > > > > > > > > > > > Other Information: > > > > > > > > After my initial and incomplete dig-up, the commit (3335068f8721 > > > > "riscv: Use PUD/P4D/PGD pages for the linear mapping")[2] > > > > is closely related to this panic. This commit uses re-defined > > > > `MIN_MEMBLOCK_ADDR` to discover the entire system memory > > > > and extends the `va_pa_offset` from `kernel_map.phys_addr` to > > > > `phys_ram_base` for linear memory mapping. > > > > > > > > If the firmware delivered the firmware memory region (like: a PMP > > > > protected region in OpenSbi) without "no-map" propriety, > > > > this commit will result in firmware memory being directly mapped by > > > > `create_linear_mapping_page_table()`. > > > > > > > > We can see the mapping via ptdump : > > > > ```c > > > > ---[ Linear mapping ]--- > > > > 0xff60000000000000-0xff60000000200000 0x0000000080000000 2M PMD D A G > > > > . . W R V ------------- the firmware memory > > > > 0xff60000000200000-0xff60000000c00000 0x0000000080200000 10M PMD D A G . . . R V > > > > 0xff60000000c00000-0xff60000001000000 0x0000000080c00000 4M PMD D A G . . W R V > > > > 0xff60000001000000-0xff60000001600000 0x0000000081000000 6M PMD D A G . . . R V > > > > 0xff60000001600000-0xff60000040000000 0x0000000081600000 1002M PMD D A > > > > G . . W R V > > > > 0xff60000040000000-0xff60000100000000 0x00000000c0000000 3G PUD D A G . . W R V > > > > ---[ Modules/BPF mapping ]--- > > > > ---[ Kernel mapping ]--- > > > > 0xffffffff80000000-0xffffffff80a00000 0x0000000080200000 10M PMD D A G . X . R V > > > > 0xffffffff80a00000-0xffffffff80c00000 0x0000000080c00000 2M PMD D A G . . . R V > > > > 0xffffffff80c00000-0xffffffff80e00000 0x0000000080e00000 2M PMD D A G . . W R V > > > > 0xffffffff80e00000-0xffffffff81400000 0x0000000081000000 6M PMD D A G . . . R V > > > > 0xffffffff81400000-0xffffffff81800000 0x0000000081600000 4M PMD > > > > ``` > > > > > > > > In the hibernation process, `swsusp_save()` calls > > > > `copy_data_pages(©_bm, &orig_bm)` to copy these two memory > > > > bitmaps, > > > > the Oops(load access fault) occurred while copying the page of > > > > PAGE_OFFSET (which maps the firmware memory). > > > > > > I'm not saying that the hibernation process is in fault here, but > > > that's weird that it is trying to access pages that are not available > > > to the kernel: this region is mapped in the page table so that we can > > > use a 1GB page, but it is reserved so that it is not added to the > > > kernel memory pool. > Yes, my fault, the Test2 is not a correct testcase. > > > > > > > > > > > I also did two other tests: > > > > Test1: > > > > > > > > The hibernation works well in the kernel with the commit 3335068f8721 > > > > reverted at least in the current environment. > > > > > > > > Test2: > > > > > > > > I built a simple kernel module to simulate the access of the value of > > > > `PAGE_OFFSET` address, and the same panic occurred with the load > > > > access fault. > > > > So hibernation seems not the only case to trigger this panic. > > > > > > > > Finally, should we always leave the firmware memory with > > > > `MEMBLOCK_NOMAP` flag by some efforts from Linux or OpenSbi (at least > > > > in the current environment) or any other suggestions? > > > > > > > > > > I actually removed this flag a few years ago, and I have to admit that > > > I need to check if that's necessary: the goal of commit 3335068f8721 > > > ("riscv: Use PUD/P4D/PGD pages for the linear mapping") is to expose > > > the "right" start of DRAM so that we can align virtual and physical > > > addresses on a 1GB boundary. > > > > > > So I have to check if a nomap region is actually added as a > > > memblock.memory.regions[] or not: if yes, that's perfect, let's add > > > the nomap attributes to the PMP regions, otherwise, I don't think that > > > is a good solution. > > > > So here is the current linear mapping without nomap in openSBI: > > > > ---[ Linear mapping ]--- > > 0xff60000000000000-0xff60000000200000 0x0000000080000000 2M > > PMD D A G . . W R V > > 0xff60000000200000-0xff60000000e00000 0x0000000080200000 12M > > PMD D A G . . . R V > > > > And below the linear mapping with nomap in openSBI: > > > > ---[ Linear mapping ]--- > > 0xff60000000080000-0xff60000000200000 0x0000000080080000 1536K > > PTE D A G . . W R V > > 0xff60000000200000-0xff60000000e00000 0x0000000080200000 12M > > PMD D A G . . . R V > > > > So adding nomap does not misalign virtual and physical addresses, it > > prevents the usage of 1GB page for this area though, so that's a > > solution, we just lose this 1GB page here. > > > > But even though that may be the fix, I think we also need to fix that > > in the kernel as it would break compatibility with certain versions of > > openSBI *if* we fix openSBI...So here are a few solutions: > > > > 1. we can mark all "mmode_resv" nodes in the device tree as nomap, > > before the linear mapping is established (IIUC, those nodes are added > > by openSBI to advertise PMP regions) > > -> This amounts to the same fix as opensbi and we lose the 1GB hugepage. > > 2. we can tweak pfn_is_nosave function to *not* save pfn corresponding > > to PMP regions > > -> We don't lose the 1GB hugepage \o/ > > 3. we can use register_nosave_region() to not save the "mmode_resv" > > regions (x86 does that > > https://elixir.bootlin.com/linux/v6.4-rc1/source/arch/x86/kernel/e820.c#L753) > > -> We don't lose the 1GB hugepage \o/ > > 4. Given JeeHeng pointer to > > https://elixir.bootlin.com/linux/v6.4-rc1/source/kernel/power/snapshot.c#L1340, > > we can mark those pages as non-readable and make the hibernation > > process not save those pages > > -> Very late-in-the-day idea, not sure what it's worth, we also > > lose the 1GB hugepage... > > > > To me, the best solution is 3 as it would prepare for other similar > > issues later, it is similar to x86 and it allows us to keep 1GB > > hugepages. > > I agree, > register_nosave_region() is a good way in the early initialization to > set page frames (like the PMP regions) in forbidden_pages_map and mark > them as no-savable for hibernation. > > Look forward to your fixing. Please find below the patch in question, which worked for me, if you can give it a try. As mentioned by Conor, I'd like to make sure the mmode_resv "interface" is really what we need to use before upstreaming this fix @Anup Patel @Atish Kumar Patra static int sleep_cpu = -EINVAL; @@ -67,6 +69,45 @@ static void arch_hdr_invariants(struct arch_hibernate_hdr_invariants *i) memcpy(i->uts_version, init_utsname()->version, sizeof(i->uts_version)); } +void __init register_nosave_regions(void) +{ +#define MMODE_RESV "mmode_resv" + int node, child; + const void *fdt = initial_boot_params; + + node = fdt_path_offset(fdt, "/reserved-memory"); + if (node < 0) + return; + + fdt_for_each_subnode(child, fdt, node) { + phys_addr_t base, size; + const __be32 *prop; + const char *uname; + int len; + int t_len = (dt_root_addr_cells + dt_root_size_cells) * sizeof(__be32); + + uname = fdt_get_name(fdt, child, NULL); + + if (!uname || strncmp(uname, MMODE_RESV, sizeof(MMODE_RESV) - 1)) + continue; + + prop = of_get_flat_dt_prop(child, "reg", &len); + if (!prop) + continue; + + while (len >= t_len) { + base = dt_mem_next_cell(dt_root_addr_cells, &prop); + size = dt_mem_next_cell(dt_root_size_cells, &prop); + + if (size) + register_nosave_region(phys_to_pfn(base), + phys_to_pfn(base + size)); + + len -= t_len; + } + } +} + /* * Check if the given pfn is in the 'nosave' section. */ @@ -421,6 +462,8 @@ static int __init riscv_hibernate_init(void) if (WARN_ON(!hibernate_cpu_context)) return -ENOMEM; + register_nosave_regions(); + return 0; } > > > > I have been thinking, and to me nomap does not provide anything since > > the kernel should not address this memory range, so if it does, we > > must fix the kernel. > > > > Let me know what you all think, I'll be preparing a PoC of 3 in the meantime! > > > > Alex > > > > > > > > > > > > And a last word: Mike Rapoport recently gave a speech [1] where he > > > states that mapping the linear mapping with hugepages does not give > > > rise to better performance so *maybe* reverting this commit may be a > > > solution too as it may not provide the expected benefits (even though > > > I'd rather have it and another benefit of mapping the linear mapping > > > with 1GB hugepages is that it is faster to boot, but that needs to be > > > measured). > > > > > > [1] https://lwn.net/Articles/931406/ > > > > > > > Please correct me if I'm wrong. > > > > > > > > [1]: https://lore.kernel.org/r/20230330064321.1008373-5-jeeheng.sia@starfivetech.com > > > > [2]: https://lore.kernel.org/r/20230324155421.271544-4-alexghiti@rivosinc.com > > > > > > > > -- > > > > Thanks, > > > > Song > > > > > > Thanks for the thorough report! > > > > > > Alex > > > > -- > Thanks, > Song diff --git a/arch/riscv/kernel/hibernate.c b/arch/riscv/kernel/hibernate.c index 264b2dcdd67e..9ad8bf5c956b 100644 --- a/arch/riscv/kernel/hibernate.c +++ b/arch/riscv/kernel/hibernate.c @@ -24,6 +24,8 @@ #include #include #include +#include +#include /* The logical cpu number we should resume on, initialised to a non-cpu number. */