1. 06 Nov, 2017 17 commits
  2. 22 Oct, 2017 12 commits
  3. 20 Oct, 2017 6 commits
    • Michael Neuling's avatar
      powerpc/tm: P9 disable transactionally suspended sigcontexts · 92fb8690
      Michael Neuling authored
      Unfortunately userspace can construct a sigcontext which enables
      suspend. Thus userspace can force Linux into a path where trechkpt is
      executed.
      
      This patch blocks this from happening on POWER9 by sanity checking
      sigcontexts passed in.
      
      ptrace doesn't have this problem as only MSR SE and BE can be changed
      via ptrace.
      
      This patch also adds a number of WARN_ON()s in case we ever enter
      suspend when we shouldn't. This should not happen, but if it does the
      symptoms are soft lockup warnings which are not obviously TM related,
      so the WARN_ON()s should make it obvious what's happening.
      Signed-off-by: default avatarMichael Neuling <mikey@neuling.org>
      Signed-off-by: default avatarCyril Bur <cyrilbur@gmail.com>
      Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
      92fb8690
    • Michael Ellerman's avatar
      powerpc/powernv: Enable TM without suspend if possible · 54820530
      Michael Ellerman authored
      Some Power9 revisions can run in a mode where TM operates without
      suspended state. If we find ourself on a CPU that might be in this
      mode, we query OPAL to check, and if so we reenable TM in CPU
      features, and enable a new user feature to signal to userspace that we
      are in this mode.
      
      We do not enable the "normal" user feature, PPC_FEATURE2_HTM, but we
      do enable PPC_FEATURE2_HTM_NOSC because that indicates to userspace
      that the kernel will abort transactions on syscall entry, which is
      true regardless of the suspend mode.
      Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
      54820530
    • Michael Ellerman's avatar
      powerpc: Add PPC_FEATURE2_HTM_NO_SUSPEND · cba6ac48
      Michael Ellerman authored
      Some CPUs can operate in a mode where TM (Transactional Memory) is
      enabled but the suspended state of TM is disabled. In this mode
      tsuspend does not enter suspended state, instead the transaction is
      aborted. Similarly any other event that would lead to suspended state
      instead aborts the transaction.
      
      There is also an ABI change, in that in this mode processes are not
      allowed to sigreturn with an MSR that would lead to suspended state,
      Linux will instead return an error to the sigreturn syscall.
      Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
      cba6ac48
    • Cyril Bur's avatar
      powerpc/tm: Add commandline option to disable hardware transactional memory · 07fd1761
      Cyril Bur authored
      Currently the kernel relies on firmware to inform it whether or not the
      CPU supports HTM and as long as the kernel was built with
      CONFIG_PPC_TRANSACTIONAL_MEM=y then it will allow userspace to make
      use of the facility.
      
      There may be situations where it would be advantageous for the kernel
      to not allow userspace to use HTM, currently the only way to achieve
      this is to recompile the kernel with CONFIG_PPC_TRANSACTIONAL_MEM=n.
      
      This patch adds a simple commandline option so that HTM can be
      disabled at boot time.
      Signed-off-by: default avatarCyril Bur <cyrilbur@gmail.com>
      [mpe: Simplify to a bool, move to prom.c, put doco in the right place.
       Always disable, regardless of initial state, to avoid user confusion.]
      Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
      07fd1761
    • Michael Ellerman's avatar
      Merge branch 'topic/ppc-kvm' into next · ddd46ed2
      Michael Ellerman authored
      Bring in some KVM commits we need (the TM one in particular).
      ddd46ed2
    • Michael Ellerman's avatar
      KVM: PPC: Tie KVM_CAP_PPC_HTM to the user-visible TM feature · 2a3d6553
      Michael Ellerman authored
      Currently we use CPU_FTR_TM to decide if the CPU/kernel can support
      TM (Transactional Memory), and if it's true we advertise that to
      Qemu (or similar) via KVM_CAP_PPC_HTM.
      
      PPC_FEATURE2_HTM is the user-visible feature bit, which indicates that
      the CPU and kernel can support TM. Currently CPU_FTR_TM and
      PPC_FEATURE2_HTM always have the same value, either true or false, so
      using the former for KVM_CAP_PPC_HTM is correct.
      
      However some Power9 CPUs can operate in a mode where TM is enabled but
      TM suspended state is disabled. In this mode CPU_FTR_TM is true, but
      PPC_FEATURE2_HTM is false. Instead a different PPC_FEATURE2 bit is
      set, to indicate that this different mode of TM is available.
      
      It is not safe to let guests use TM as-is, when the CPU is in this
      mode. So to prevent that from happening, use PPC_FEATURE2_HTM to
      determine the value of KVM_CAP_PPC_HTM.
      Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
      2a3d6553
  4. 19 Oct, 2017 1 commit
  5. 16 Oct, 2017 4 commits