kernel.git/arch/powerpc/kernel/exceptions-64s.S, branch linux-5.9.y

powerpc/64s/exception: KVM Fix for host DSI being taken in HPT guest MMU context

2020-12-02T07:51:45Z

commit cd81acc600a9684ea4b4d25a47900d38a3890eab upstream. Commit 2284ffea8f0c ("powerpc/64s/exception: Only test KVM in SRR interrupts when PR KVM is supported") removed KVM guest tests from interrupts that do not set HV=1, when PR-KVM is not configured. This is wrong for HV-KVM HPT guest MMIO emulation case which attempts to load the faulting instruction word with MSR[DR]=1 and MSR[HV]=1 with the guest MMU context loaded. This can cause host DSI, DSLB interrupts which must test for KVM guest. Restore this and add a comment. Fixes: 2284ffea8f0c ("powerpc/64s/exception: Only test KVM in SRR interrupts when PR KVM is supported") Cc: stable@vger.kernel.org # v5.7+ Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20201117135617.3521127-1-npiggin@gmail.com Signed-off-by: Greg Kroah-Hartman

powerpc/64s: Fix KVM system reset handling when CONFIG_PPC_PSERIES=y

2020-12-02T07:51:45Z

commit 575cba20c421ecb6b563ae352e4e0468e4ca8b3c upstream. pseries guest kernels have a FWNMI handler for SRESET and MCE NMIs, which is basically the same as the regular handlers for those interrupts. The system reset FWNMI handler did not have a KVM guest test in it, although it probably should have because the guest can itself run guests. Commit 4f50541f6703b ("powerpc/64s/exception: Move all interrupt handlers to new style code gen macros") convert the handler faithfully to avoid a KVM test with a "clever" trick to modify the IKVM_REAL setting to 0 when the fwnmi handler is to be generated (PPC_PSERIES=y). This worked when the KVM test was generated in the interrupt entry handlers, but a later patch moved the KVM test to the common handler, and the common handler macro is expanded below the fwnmi entry. This prevents the KVM test from being generated even for the 0x100 entry point as well. The result is NMI IPIs in the host kernel when a guest is running will use gest registers. This goes particularly badly when an HPT guest is running and the MMU is set to guest mode. Remove this trickery and just generate the test always. Fixes: 9600f261acaa ("powerpc/64s/exception: Move KVM test to common code") Cc: stable@vger.kernel.org # v5.7+ Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20201114114743.3306283-1-npiggin@gmail.com Signed-off-by: Greg Kroah-Hartman

powerpc/64s: flush L1D after user accesses

2020-11-22T09:15:32Z

commit 9a32a7e78bd0cd9a9b6332cbdc345ee5ffd0c5de upstream. IBM Power9 processors can speculatively operate on data in the L1 cache before it has been completely validated, via a way-prediction mechanism. It is not possible for an attacker to determine the contents of impermissible memory using this method, since these systems implement a combination of hardware and software security measures to prevent scenarios where protected data could be leaked. However these measures don't address the scenario where an attacker induces the operating system to speculatively execute instructions using data that the attacker controls. This can be used for example to speculatively bypass "kernel user access prevention" techniques, as discovered by Anthony Steinhauser of Google's Safeside Project. This is not an attack by itself, but there is a possibility it could be used in conjunction with side-channels or other weaknesses in the privileged code to construct an attack. This issue can be mitigated by flushing the L1 cache between privilege boundaries of concern. This patch flushes the L1 cache after user accesses. This is part of the fix for CVE-2020-4788. Signed-off-by: Nicholas Piggin Signed-off-by: Daniel Axtens Signed-off-by: Greg Kroah-Hartman

powerpc/64s: flush L1D on kernel entry

2020-11-22T09:15:32Z

commit f79643787e0a0762d2409b7b8334e83f22d85695 upstream. IBM Power9 processors can speculatively operate on data in the L1 cache before it has been completely validated, via a way-prediction mechanism. It is not possible for an attacker to determine the contents of impermissible memory using this method, since these systems implement a combination of hardware and software security measures to prevent scenarios where protected data could be leaked. However these measures don't address the scenario where an attacker induces the operating system to speculatively execute instructions using data that the attacker controls. This can be used for example to speculatively bypass "kernel user access prevention" techniques, as discovered by Anthony Steinhauser of Google's Safeside Project. This is not an attack by itself, but there is a possibility it could be used in conjunction with side-channels or other weaknesses in the privileged code to construct an attack. This issue can be mitigated by flushing the L1 cache between privilege boundaries of concern. This patch flushes the L1 cache on kernel entry. This is part of the fix for CVE-2020-4788. Signed-off-by: Nicholas Piggin Signed-off-by: Daniel Axtens Signed-off-by: Greg Kroah-Hartman

Merge tag 'powerpc-5.9-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

2020-08-07T17:33:50Z

Pull powerpc updates from Michael Ellerman: - Add support for (optionally) using queued spinlocks & rwlocks. - Support for a new faster system call ABI using the scv instruction on Power9 or later. - Drop support for the PROT_SAO mmap/mprotect flag as it will be unsupported on Power10 and future processors, leaving us with no way to implement the functionality it requests. This risks breaking userspace, though we believe it is unused in practice. - A bug fix for, and then the removal of, our custom stack expansion checking. We now allow stack expansion up to the rlimit, like other architectures. - Remove the remnants of our (previously disabled) topology update code, which tried to react to NUMA layout changes on virtualised systems, but was prone to crashes and other problems. - Add PMU support for Power10 CPUs. - A change to our signal trampoline so that we don't unbalance the link stack (branch return predictor) in the signal delivery path. - Lots of other cleanups, refactorings, smaller features and so on as usual. Thanks to: Abhishek Goel, Alastair D'Silva, Alexander A. Klimov, Alexey Kardashevskiy, Alistair Popple, Andrew Donnellan, Aneesh Kumar K.V, Anju T Sudhakar, Anton Blanchard, Arnd Bergmann, Athira Rajeev, Balamuruhan S, Bharata B Rao, Bill Wendling, Bin Meng, Cédric Le Goater, Chris Packham, Christophe Leroy, Christoph Hellwig, Daniel Axtens, Dan Williams, David Lamparter, Desnes A. Nunes do Rosario, Erhard F., Finn Thain, Frederic Barrat, Ganesh Goudar, Gautham R. Shenoy, Geoff Levand, Greg Kurz, Gustavo A. R. Silva, Hari Bathini, Harish, Imre Kaloz, Joel Stanley, Joe Perches, John Crispin, Jordan Niethe, Kajol Jain, Kamalesh Babulal, Kees Cook, Laurent Dufour, Leonardo Bras, Li RongQing, Madhavan Srinivasan, Mahesh Salgaonkar, Mark Cave-Ayland, Michal Suchanek, Milton Miller, Mimi Zohar, Murilo Opsfelder Araujo, Nathan Chancellor, Nathan Lynch, Naveen N. Rao, Nayna Jain, Nicholas Piggin, Oliver O'Halloran, Palmer Dabbelt, Pedro Miraglia Franco de Carvalho, Philippe Bergheaud, Pingfan Liu, Pratik Rajesh Sampat, Qian Cai, Qinglang Miao, Randy Dunlap, Ravi Bangoria, Sachin Sant, Sam Bobroff, Sandipan Das, Santosh Sivaraj, Satheesh Rajendran, Shirisha Ganta, Sourabh Jain, Srikar Dronamraju, Stan Johnson, Stephen Rothwell, Thadeu Lima de Souza Cascardo, Thiago Jung Bauermann, Tom Lane, Vaibhav Jain, Vladis Dronov, Wei Yongjun, Wen Xiong, YueHaibing. * tag 'powerpc-5.9-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: (337 commits) selftests/powerpc: Fix pkey syscall redefinitions powerpc: Fix circular dependency between percpu.h and mmu.h powerpc/powernv/sriov: Fix use of uninitialised variable selftests/powerpc: Skip vmx/vsx/tar/etc tests on older CPUs powerpc/40x: Fix assembler warning about r0 powerpc/papr_scm: Add support for fetching nvdimm 'fuel-gauge' metric powerpc/papr_scm: Fetch nvdimm performance stats from PHYP cpuidle: pseries: Fixup exit latency for CEDE(0) cpuidle: pseries: Add function to parse extended CEDE records cpuidle: pseries: Set the latency-hint before entering CEDE selftests/powerpc: Fix online CPU selection powerpc/perf: Consolidate perf_callchain_user_[64|32]() powerpc/pseries/hotplug-cpu: Remove double free in error path powerpc/pseries/mobility: Add pr_debug() for device tree changes powerpc/pseries/mobility: Set pr_fmt() powerpc/cacheinfo: Warn if cache object chain becomes unordered powerpc/cacheinfo: Improve diagnostics about malformed cache lists powerpc/cacheinfo: Use name@unit instead of full DT path in debug messages powerpc/cacheinfo: Set pr_fmt() powerpc: fix function annotations to avoid section mismatch warnings with gcc-10 ...

powerpc/64s/hash: Fix hash_preload running with interrupts enabled

2020-07-27T07:02:09Z

Commit 2f92447f9f96 ("powerpc/book3s64/hash: Use the pte_t address from the caller") removed the local_irq_disable from hash_preload, but it was required for more than just the page table walk: the hash pte busy bit is effectively a lock which may be taken in interrupt context, and the local update flag test must not be preempted before it's used. This solves apparent lockups with perf interrupting __hash_page_64K. If get_perf_callchain then also takes a hash fault on the same page while it is already locked, it will loop forever taking hash faults, which looks like this: cpu 0x49e: Vector: 100 (System Reset) at [c00000001a4f7d70] pc: c000000000072dc8: hash_page_mm+0x8/0x800 lr: c00000000000c5a4: do_hash_page+0x24/0x38 sp: c0002ac1cc69ac70 msr: 8000000000081033 current = 0xc0002ac1cc602e00 paca = 0xc00000001de1f280 irqmask: 0x03 irq_happened: 0x01 pid = 20118, comm = pread2_processe Linux version 5.8.0-rc6-00345-g1fad14f18bc6 49e:mon> t [c0002ac1cc69ac70] c00000000000c5a4 do_hash_page+0x24/0x38 (unreliable) --- Exception: 300 (Data Access) at c00000000008fa60 __copy_tofrom_user_power7+0x20c/0x7ac [link register ] c000000000335d10 copy_from_user_nofault+0xf0/0x150 [c0002ac1cc69af70] c00032bf9fa3c880 (unreliable) [c0002ac1cc69afa0] c000000000109df0 read_user_stack_64+0x70/0xf0 [c0002ac1cc69afd0] c000000000109fcc perf_callchain_user_64+0x15c/0x410 [c0002ac1cc69b060] c000000000109c00 perf_callchain_user+0x20/0x40 [c0002ac1cc69b080] c00000000031c6cc get_perf_callchain+0x25c/0x360 [c0002ac1cc69b120] c000000000316b50 perf_callchain+0x70/0xa0 [c0002ac1cc69b140] c000000000316ddc perf_prepare_sample+0x25c/0x790 [c0002ac1cc69b1a0] c000000000317350 perf_event_output_forward+0x40/0xb0 [c0002ac1cc69b220] c000000000306138 __perf_event_overflow+0x88/0x1a0 [c0002ac1cc69b270] c00000000010cf70 record_and_restart+0x230/0x750 [c0002ac1cc69b620] c00000000010d69c perf_event_interrupt+0x20c/0x510 [c0002ac1cc69b730] c000000000027d9c performance_monitor_exception+0x4c/0x60 [c0002ac1cc69b750] c00000000000b2f8 performance_monitor_common_virt+0x1b8/0x1c0 --- Exception: f00 (Performance Monitor) at c0000000000cb5b0 pSeries_lpar_hpte_insert+0x0/0x160 [link register ] c0000000000846f0 __hash_page_64K+0x210/0x540 [c0002ac1cc69ba50] 0000000000000000 (unreliable) [c0002ac1cc69bb00] c000000000073ae0 update_mmu_cache+0x390/0x3a0 [c0002ac1cc69bb70] c00000000037f024 wp_page_copy+0x364/0xce0 [c0002ac1cc69bc20] c00000000038272c do_wp_page+0xdc/0xa60 [c0002ac1cc69bc70] c0000000003857bc handle_mm_fault+0xb9c/0x1b60 [c0002ac1cc69bd50] c00000000006c434 __do_page_fault+0x314/0xc90 [c0002ac1cc69be20] c00000000000c5c8 handle_page_fault+0x10/0x2c --- Exception: 300 (Data Access) at 00007fff8c861fe8 SP (7ffff6b19660) is in userspace Fixes: 2f92447f9f96 ("powerpc/book3s64/hash: Use the pte_t address from the caller") Reported-by: Athira Rajeev Reported-by: Anton Blanchard Signed-off-by: Nicholas Piggin Reviewed-by: Aneesh Kumar K.V Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20200727060947.10060-1-npiggin@gmail.com

Merge branch 'scv' support into next

2020-07-23T07:43:44Z

From Nick's cover letter: Linux powerpc new system call instruction and ABI System Call Vectored (scv) ABI ============================== The scv instruction is introduced with POWER9 / ISA3, it comes with an rfscv counter-part. The benefit of these instructions is performance (trading slower SRR0/1 with faster LR/CTR registers, and entering the kernel with MSR[EE] and MSR[RI] left enabled, which can reduce MSR updates. The scv instruction has 128 levels (not enough to cover the Linux system call space). Assignment and advertisement ---------------------------- The proposal is to assign scv levels conservatively, and advertise them with HWCAP feature bits as we add support for more. Linux has not enabled FSCR[SCV] yet, so executing the scv instruction will cause the kernel to log a "SCV facility unavilable" message, and deliver a SIGILL with ILL_ILLOPC to the process. Linux has defined a HWCAP2 bit PPC_FEATURE2_SCV for SCV support, but does not set it. This change allocates the zero level ('scv 0'), advertised with PPC_FEATURE2_SCV, which will be used to provide normal Linux system calls (equivalent to 'sc'). Attempting to execute scv with other levels will cause a SIGILL to be delivered the same as before, but will not log a "SCV facility unavailable" message (because the processor facility is enabled). Calling convention ------------------ The proposal is for scv 0 to provide the standard Linux system call ABI with the following differences from sc convention[1]: - LR is to be volatile across scv calls. This is necessary because the scv instruction clobbers LR. From previous discussion, this should be possible to deal with in GCC clobbers and CFI. - cr1 and cr5-cr7 are volatile. This matches the C ABI and would allow the kernel system call exit to avoid restoring the volatile cr registers (although we probably still would anyway to avoid information leaks). - Error handling: The consensus among kernel, glibc, and musl is to move to using negative return values in r3 rather than CR0[SO]=1 to indicate error, which matches most other architectures, and is closer to a function call. Notes ----- - r0,r4-r8 are documented as volatile in the ABI, but the kernel patch as submitted currently preserves them. This is to leave room for deciding which way to go with these. Some small benefit was found by preserving them[1] but I'm not convinced it's worth deviating from the C function call ABI just for this. Release code should follow the ABI. Previous discussions: https://lists.ozlabs.org/pipermail/linuxppc-dev/2020-April/208691.html https://lists.ozlabs.org/pipermail/linuxppc-dev/2020-April/209268.html [1] https://github.com/torvalds/linux/blob/master/Documentation/powerpc/syscall64-abi.rst [2] https://lists.ozlabs.org/pipermail/linuxppc-dev/2020-April/209263.html

powerpc/64s: system call support for scv/rfscv instructions

2020-07-22T13:00:27Z

Add support for the scv instruction on POWER9 and later CPUs. For now this implements the zeroth scv vector 'scv 0', as identical to 'sc' system calls, with the exception that LR is not preserved, nor are volatile CR registers, and error is not indicated with CR0[SO], but by returning a negative errno. rfscv is implemented to return from scv type system calls. It can not be used to return from sc system calls because those are defined to preserve LR. getpid syscall throughput on POWER9 is improved by 26% (428 to 318 cycles), largely due to reducing mtmsr and mtspr. Signed-off-by: Nicholas Piggin [mpe: Fix ppc64e build] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20200611081203.995112-3-npiggin@gmail.com

powerpc/64s/exception: treat NIA below __end_interrupts as soft-masked

2020-07-22T13:00:23Z

The scv instruction causes an interrupt which can enter the kernel with MSR[EE]=1, thus allowing interrupts to hit at any time. These must not be taken as normal interrupts, because they come from MSR[PR]=0 context, and yet the kernel stack is not yet set up and r13 is not set to the PACA). Treat this as a soft-masked interrupt regardless of the soft masked state. This does not affect behaviour yet, because currently all interrupts are taken with MSR[EE]=0. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20200611081203.995112-2-npiggin@gmail.com

powerpc/64s/exception: Fix 0x1500 interrupt handler crash

2020-07-08T10:41:06Z

A typo caused the interrupt handler to branch immediately to the common "unknown interrupt" handler and skip the special case test for denormal cause. This does not affect KVM softpatch handling (e.g., for POWER9 TM assist) because the KVM test was moved to common code by commit 9600f261acaa ("powerpc/64s/exception: Move KVM test to common code") just before this bug was introduced. Fixes: 3f7fbd97d07d ("powerpc/64s/exception: Clean up SRR specifiers") Reported-by: Paul Menzel Signed-off-by: Nicholas Piggin Tested-by: Paul Menzel [mpe: Split selftest into a separate patch] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20200708074942.1713396-1-npiggin@gmail.com