kernel/arch/powerpc/mm/mmu_context.c, branch linux-6.2.y

powerpc/mm: Switch obsolete dssall to .long

2021-12-23T11:35:13Z

The dssall ("Data Stream Stop All") instruction is obsolete altogether with other Data Cache Instructions since ISA 2.03 (year 2006). LLVM IAS does not support it but PPC970 seems to be using it. This switches dssall to .long as there is no much point in fixing LLVM. Signed-off-by: Alexey Kardashevskiy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20211221055904.555763-6-aik@ozlabs.ru

powerpc: Add KUAP support for BOOKE and 40x

2021-12-09T11:41:19Z

On booke/40x we don't have segments like book3s/32. On booke/40x we don't have access protection groups like 8xx. Use the PID register to provide user access protection. Kernel address space can be accessed with any PID. User address space has to be accessed with the PID of the user. User PID is always not null. Everytime the kernel is entered, set PID register to 0 and restore PID register when returning to user. Everytime kernel needs to access user data, PID is restored for the access. In TLB miss handlers, check the PID and bail out to data storage exception when PID is 0 and accessed address is in user space. Note that also forbids execution of user text by kernel except when user access is unlocked. But this shouldn't be a problem as the kernel is not supposed to ever run user text. This patch prepares the infrastructure but the real activation of KUAP is done by following patches for each processor type one by one. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/5d65576a8e31e9480415785a180c92dd4e72306d.1634627931.git.christophe.leroy@csgroup.eu

powerpc/32s: Save content of sr0 to avoid 'mfsr'

2021-12-09T11:41:17Z

Calling 'mfsr' to get the content of segment registers is heavy, in addition it requires clearing of the 'reserved' bits. In order to avoid this operation, save it in mm context and in thread struct. The saved sr0 is the one used by kernel, this means that on locking entry it can be used as is. For unlocking, the only thing to do is to clear SR_NX. This improves null_syscall selftest by 12 cycles, ie 4%. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/b02baf2ed8f09bad910dfaeeb7353b2ae6830525.1634627931.git.christophe.leroy@csgroup.eu

KVM: PPC: Book3S HV: Implement radix prefetch workaround by disabling MMU

2021-06-10T12:12:14Z

Rather than partition the guest PID space + flush a rogue guest PID to work around this problem, instead fix it by always disabling the MMU when switching in or out of guest MMU context in HV mode. This may be a bit less efficient, but it is a lot less complicated and allows the P9 path to trivally implement the workaround too. Newer CPUs are not subject to this issue. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210528090752.3542186-22-npiggin@gmail.com

powerpc/64s: Fix mm_cpumask memory ordering comment

2021-04-22T15:38:03Z

The memory ordering comment no longer applies, because mm_ctx_id is no longer used anywhere. At best always been difficult to follow. It's better to consider the load on which the slbmte depends on, which the MMU depends on before it can start loading TLBs, rather than a store which may or may not have a subsequent dependency chain to the slbmte. So update the comment and we use the load of the mm's user context ID. This is much more analogous the radix ordering too, which is good. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210421151733.212858-1-npiggin@gmail.com

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152

2019-05-30T18:26:32Z

Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation either version 2 of the license or at your option any later version extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 3029 file(s). Signed-off-by: Thomas Gleixner Reviewed-by: Allison Randal Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de Signed-off-by: Greg Kroah-Hartman

powerpc/mm: convert Book3E 64 to pte_fragment

2019-05-02T15:20:24Z

Book3E 64 is the only subarch not using pte_fragment. In order to allow refactorisation, this patch converts it to pte_fragment. Reviewed-by: Aneesh Kumar K.V Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman

powerpc/mm: Extend pte_fragment functionality to PPC32

2018-12-04T08:45:01Z

In order to allow the 8xx to handle pte_fragments, this patch extends the use of pte_fragments to PPC32 platforms. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman

powerpc/64s/radix: optimise pte_update

2018-06-03T10:40:36Z

Implementing pte_update with pte_xchg (which uses cmpxchg) is inefficient. A single larx/stcx. works fine, no need for the less efficient cmpxchg sequence. Then remove the memory barriers from the operation. There is a requirement for TLB flushing to load mm_cpumask after the store that reduces pte permissions, which is moved into the TLB flush code. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman

powerpc, membarrier: Skip memory barrier in switch_mm()

2018-02-05T20:34:02Z

Allow PowerPC to skip the full memory barrier in switch_mm(), and only issue the barrier when scheduling into a task belonging to a process that has registered to use expedited private. Threads targeting the same VM but which belong to different thread groups is a tricky case. It has a few consequences: It turns out that we cannot rely on get_nr_threads(p) to count the number of threads using a VM. We can use (atomic_read(&mm->mm_users) == 1 && get_nr_threads(p) == 1) instead to skip the synchronize_sched() for cases where the VM only has a single user, and that user only has a single thread. It also turns out that we cannot use for_each_thread() to set thread flags in all threads using a VM, as it only iterates on the thread group. Therefore, test the membarrier state variable directly rather than relying on thread flags. This means membarrier_register_private_expedited() needs to set the MEMBARRIER_STATE_PRIVATE_EXPEDITED flag, issue synchronize_sched(), and only then set MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY which allows private expedited membarrier commands to succeed. membarrier_arch_switch_mm() now tests for the MEMBARRIER_STATE_PRIVATE_EXPEDITED flag. Signed-off-by: Mathieu Desnoyers Acked-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Cc: Alan Stern Cc: Alexander Viro Cc: Andrea Parri Cc: Andrew Hunter Cc: Andy Lutomirski Cc: Avi Kivity Cc: Benjamin Herrenschmidt Cc: Boqun Feng Cc: Dave Watson Cc: David Sehr Cc: Greg Hackmann Cc: Linus Torvalds Cc: Maged Michael Cc: Michael Ellerman Cc: Nicholas Piggin Cc: Paul E. McKenney Cc: Paul Mackerras Cc: Russell King Cc: Will Deacon Cc: linux-api@vger.kernel.org Cc: linux-arch@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Link: http://lkml.kernel.org/r/20180129202020.8515-3-mathieu.desnoyers@efficios.com Signed-off-by: Ingo Molnar