1. 05 Aug, 2018 8 commits
    • Nicolai Stange's avatar
      x86/KVM/VMX: Don't set l1tf_flush_l1d from vmx_handle_external_intr() · 18b57ce2
      Nicolai Stange authored
      For VMEXITs caused by external interrupts, vmx_handle_external_intr()
      indirectly calls into the interrupt handlers through the host's IDT.
      It follows that these interrupts get accounted for in the
      kvm_cpu_l1tf_flush_l1d per-cpu flag.
      The subsequently executed vmx_l1d_flush() will thus be aware that some
      interrupts have happened and conduct a L1d flush anyway.
      Setting l1tf_flush_l1d from vmx_handle_external_intr() isn't needed
      anymore. Drop it.
      Signed-off-by: default avatarNicolai Stange <nstange@suse.de>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    • Nicolai Stange's avatar
      x86/irq: Let interrupt handlers set kvm_cpu_l1tf_flush_l1d · ffcba43f
      Nicolai Stange authored
      The last missing piece to having vmx_l1d_flush() take interrupts after
      VMEXIT into account is to set the kvm_cpu_l1tf_flush_l1d per-cpu flag on
      irq entry.
      Issue calls to kvm_set_cpu_l1tf_flush_l1d() from entering_irq(),
      ipi_entering_ack_irq(), smp_reschedule_interrupt() and
      Suggested-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      Signed-off-by: default avatarNicolai Stange <nstange@suse.de>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    • Nicolai Stange's avatar
      x86: Don't include linux/irq.h from asm/hardirq.h · 447ae316
      Nicolai Stange authored
      The next patch in this series will have to make the definition of
      irq_cpustat_t available to entering_irq().
      Inclusion of asm/hardirq.h into asm/apic.h would cause circular header
      dependencies like
      and others.
      This causes compilation errors because of the header guards becoming
      effective in the second inclusion: symbols/macros that had been defined
      before wouldn't be available to intermediate headers in the #include chain
      A possible workaround would be to move the definition of irq_cpustat_t
      into its own header and include that from both, asm/hardirq.h and
      However, this wouldn't solve the real problem, namely asm/harirq.h
      unnecessarily pulling in all the linux/irq.h cruft: nothing in
      asm/hardirq.h itself requires it. Also, note that there are some other
      archs, like e.g. arm64, which don't have that #include in their
      Remove the linux/irq.h #include from x86' asm/hardirq.h.
      Fix resulting compilation errors by adding appropriate #includes to *.c
      files as needed.
      Note that some of these *.c files could be cleaned up a bit wrt. to their
      set of #includes, but that should better be done from separate patches, if
      at all.
      Signed-off-by: default avatarNicolai Stange <nstange@suse.de>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    • Nicolai Stange's avatar
      x86/KVM/VMX: Introduce per-host-cpu analogue of l1tf_flush_l1d · 45b575c0
      Nicolai Stange authored
      Part of the L1TF mitigation for vmx includes flushing the L1D cache upon
      L1D flushes are costly and two modes of operations are provided to users:
      "always" and the more selective "conditional" mode.
      If operating in the latter, the cache would get flushed only if a host side
      code path considered unconfined had been traversed. "Unconfined" in this
      context means that it might have pulled in sensitive data like user data
      or kernel crypto keys.
      The need for L1D flushes is tracked by means of the per-vcpu flag
      l1tf_flush_l1d. KVM exit handlers considered unconfined set it. A
      vmx_l1d_flush() subsequently invoked before the next VMENTER will conduct a
      L1d flush based on its value and reset that flag again.
      Currently, interrupts delivered "normally" while in root operation between
      VMEXIT and VMENTER are not taken into account. Part of the reason is that
      these don't leave any traces and thus, the vmx code is unable to tell if
      any such has happened.
      As proposed by Paolo Bonzini, prepare for tracking all interrupts by
      introducing a new per-cpu flag, "kvm_cpu_l1tf_flush_l1d". It will be in
      strong analogy to the per-vcpu ->l1tf_flush_l1d.
      A later patch will make interrupt handlers set it.
      For the sake of cache locality, group kvm_cpu_l1tf_flush_l1d into x86'
      per-cpu irq_cpustat_t as suggested by Peter Zijlstra.
      Provide the helpers kvm_set_cpu_l1tf_flush_l1d(),
      kvm_clear_cpu_l1tf_flush_l1d() and kvm_get_cpu_l1tf_flush_l1d(). Make them
      trivial resp. non-existent for !CONFIG_KVM_INTEL as appropriate.
      Let vmx_l1d_flush() handle kvm_cpu_l1tf_flush_l1d in the same way as
      Suggested-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      Suggested-by: default avatarPeter Zijlstra <peterz@infradead.org>
      Signed-off-by: default avatarNicolai Stange <nstange@suse.de>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    • Nicolai Stange's avatar
      x86/irq: Demote irq_cpustat_t::__softirq_pending to u16 · 9aee5f8a
      Nicolai Stange authored
      An upcoming patch will extend KVM's L1TF mitigation in conditional mode
      to also cover interrupts after VMEXITs. For tracking those, stores to a
      new per-cpu flag from interrupt handlers will become necessary.
      In order to improve cache locality, this new flag will be added to x86's
      Make some space available there by shrinking the ->softirq_pending bitfield
      from 32 to 16 bits: the number of bits actually used is only NR_SOFTIRQS,
      i.e. 10.
      Suggested-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      Signed-off-by: default avatarNicolai Stange <nstange@suse.de>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    • Nicolai Stange's avatar
      x86/KVM/VMX: Move the l1tf_flush_l1d test to vmx_l1d_flush() · 5b6ccc6c
      Nicolai Stange authored
      Currently, vmx_vcpu_run() checks if l1tf_flush_l1d is set and invokes
      vmx_l1d_flush() if so.
      This test is unncessary for the "always flush L1D" mode.
      Move the check to vmx_l1d_flush()'s conditional mode code path.
      - vmx_l1d_flush() is likely to get inlined anyway and thus, there's no
        extra function call.
      - This inverts the (static) branch prediction, but there hadn't been any
        explicit likely()/unlikely() annotations before and so it stays as is.
      Signed-off-by: default avatarNicolai Stange <nstange@suse.de>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    • Nicolai Stange's avatar
      x86/KVM/VMX: Replace 'vmx_l1d_flush_always' with 'vmx_l1d_flush_cond' · 427362a1
      Nicolai Stange authored
      The vmx_l1d_flush_always static key is only ever evaluated if
      vmx_l1d_should_flush is enabled. In that case however, there are only two
      L1d flushing modes possible: "always" and "conditional".
      The "conditional" mode's implementation tends to require more sophisticated
      logic than the "always" mode.
      Avoid inverted logic by replacing the 'vmx_l1d_flush_always' static key
      with a 'vmx_l1d_flush_cond' one.
      There is no change in functionality.
      Signed-off-by: default avatarNicolai Stange <nstange@suse.de>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    • Nicolai Stange's avatar
      x86/KVM/VMX: Don't set l1tf_flush_l1d to true from vmx_l1d_flush() · 379fd0c7
      Nicolai Stange authored
      vmx_l1d_flush() gets invoked only if l1tf_flush_l1d is true. There's no
      point in setting l1tf_flush_l1d to true from there again.
      Signed-off-by: default avatarNicolai Stange <nstange@suse.de>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
  2. 24 Jul, 2018 1 commit
  3. 19 Jul, 2018 2 commits
  4. 15 Jul, 2018 1 commit
    • Jiri Kosina's avatar
      x86/speculation/l1tf: Unbreak !__HAVE_ARCH_PFN_MODIFY_ALLOWED architectures · 6c26fcd2
      Jiri Kosina authored
      pfn_modify_allowed() and arch_has_pfn_modify_check() are outside of the 
      !__ASSEMBLY__ section in include/asm-generic/pgtable.h, which confuses 
      assembler on archs that don't have __HAVE_ARCH_PFN_MODIFY_ALLOWED (e.g. 
      ia64) and breaks build:
          include/asm-generic/pgtable.h: Assembler messages:
          include/asm-generic/pgtable.h:538: Error: Unknown opcode `static inline bool pfn_modify_allowed(unsigned long pfn,pgprot_t prot)'
          include/asm-generic/pgtable.h:540: Error: Unknown opcode `return true'
          include/asm-generic/pgtable.h:543: Error: Unknown opcode `static inline bool arch_has_pfn_modify_check(void)'
          include/asm-generic/pgtable.h:545: Error: Unknown opcode `return false'
          arch/ia64/kernel/entry.S:69: Error: `mov' does not fit into bundle
      Move those two static inlines into the !__ASSEMBLY__ section so that they 
      don't confuse the asm build pass.
      Fixes: 42e4089c
       ("x86/speculation/l1tf: Disallow non privileged high MMIO PROT_NONE mappings")
      Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
  5. 13 Jul, 2018 11 commits
  6. 09 Jul, 2018 1 commit
  7. 04 Jul, 2018 10 commits
  8. 02 Jul, 2018 2 commits
    • Thomas Gleixner's avatar
      cpu/hotplug: Boot HT siblings at least once · 0cc3cd21
      Thomas Gleixner authored
      Due to the way Machine Check Exceptions work on X86 hyperthreads it's
      required to boot up _all_ logical cores at least once in order to set the
      CR4.MCE bit.
      So instead of ignoring the sibling threads right away, let them boot up
      once so they can configure themselves. After they came out of the initial
      boot stage check whether its a "secondary" sibling and cancel the operation
      which puts the CPU back into offline state.
      Reported-by: default avatarDave Hansen <dave.hansen@intel.com>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Tested-by: default avatarTony Luck <tony.luck@intel.com>
    • Thomas Gleixner's avatar
      Revert "x86/apic: Ignore secondary threads if nosmt=force" · 506a66f3
      Thomas Gleixner authored
      Dave Hansen reported, that it's outright dangerous to keep SMT siblings
      disabled completely so they are stuck in the BIOS and wait for SIPI.
      The reason is that Machine Check Exceptions are broadcasted to siblings and
      the soft disabled sibling has CR4.MCE = 0. If a MCE is delivered to a
      logical core with CR4.MCE = 0, it asserts IERR#, which shuts down or
      reboots the machine. The MCE chapter in the SDM contains the following
          Because the logical processors within a physical package are tightly
          coupled with respect to shared hardware resources, both logical
          processors are notified of machine check errors that occur within a
          given physical processor. If machine-check exceptions are enabled when
          a fatal error is reported, all the logical processors within a physical
          package are dispatched to the machine-check exception handler. If
          machine-check exceptions are disabled, the logical processors enter the
          shutdown state and assert the IERR# signal. When enabling machine-check
          exceptions, the MCE flag in control register CR4 should be set for each
          logical processor.
      Reverting the commit which ignores siblings at enumeration time solves only
      half of the problem. The core cpuhotplug logic needs to be adjusted as
      This thoughtful engineered mechanism also turns the boot process on all
      Intel HT enabled systems into a MCE lottery. MCE is enabled on the boot CPU
      before the secondary CPUs are brought up. Depending on the number of
      physical cores the window in which this situation can happen is smaller or
      larger. On a HSW-EX it's about 750ms:
      MCE is enabled on the boot CPU:
      [    0.244017] mce: CPU supports 22 MCE banks
      The corresponding sibling #72 boots:
      [    1.008005] .... node  #0, CPUs:    #72
      That means if an MCE hits on physical core 0 (logical CPUs 0 and 72)
      between these two points the machine is going to shutdown. At least it's a
      known safe state.
      It's obvious that the early boot can be hit by an MCE as well and then runs
      into the same situation because MCEs are not yet enabled on the boot CPU.
      But after enabling them on the boot CPU, it does not make any sense to
      prevent the kernel from recovering.
      Adjust the nosmt kernel parameter documentation as well.
      Reverts: 2207def7
       ("x86/apic: Ignore secondary threads if nosmt=force")
      Reported-by: default avatarDave Hansen <dave.hansen@intel.com>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Tested-by: default avatarTony Luck <tony.luck@intel.com>
  9. 29 Jun, 2018 1 commit
  10. 27 Jun, 2018 1 commit
    • Vlastimil Babka's avatar
      x86/speculation/l1tf: Protect PAE swap entries against L1TF · 0d0f6249
      Vlastimil Babka authored
      The PAE 3-level paging code currently doesn't mitigate L1TF by flipping the
      offset bits, and uses the high PTE word, thus bits 32-36 for type, 37-63 for
      offset. The lower word is zeroed, thus systems with less than 4GB memory are
      safe. With 4GB to 128GB the swap type selects the memory locations vulnerable
      to L1TF; with even more memory, also the swap offfset influences the address.
      This might be a problem with 32bit PAE guests running on large 64bit hosts.
      By continuing to keep the whole swap entry in either high or low 32bit word of
      PTE we would limit the swap size too much. Thus this patch uses the whole PAE
      PTE with the same layout as the 64bit version does. The macros just become a
      bit tricky since they assume the arch-dependent swp_entry_t to be 32bit.
      Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
  11. 22 Jun, 2018 1 commit
  12. 21 Jun, 2018 1 commit