1. 23 Jun, 2020 4 commits
    • Sean Christopherson's avatar
      KVM: VMX: Remove vcpu_vmx's defunct copy of host_pkru · e4553b49
      Sean Christopherson authored
      Remove vcpu_vmx.host_pkru, which got left behind when PKRU support was
      moved to common x86 code.
      No functional change intended.
      Fixes: 37486135
       ("KVM: x86: Fix pkru save/restore when guest CR4.PKE=0, move it to x86.c")
      Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
      Message-Id: <20200617034123.25647-1-sean.j.christopherson@intel.com>
      Reviewed-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
      Reviewed-by: default avatarJim Mattson <jmattson@google.com>
      Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    • Marcelo Tosatti's avatar
      KVM: x86: allow TSC to differ by NTP correction bounds without TSC scaling · 26769f96
      Marcelo Tosatti authored
      The Linux TSC calibration procedure is subject to small variations
      (its common to see +-1 kHz difference between reboots on a given CPU, for example).
      So migrating a guest between two hosts with identical processor can fail, in case
      of a small variation in calibrated TSC between them.
      Without TSC scaling, the current kernel interface will either return an error
      (if user_tsc_khz <= tsc_khz) or enable TSC catchup mode.
      This change enables the following TSC tolerance check to
      accept KVM_SET_TSC_KHZ within tsc_tolerance_ppm (which is 250ppm by default).
               * Compute the variation in TSC rate which is acceptable
               * within the range of tolerance and decide if the
               * rate being applied is within that bounds of the hardware
               * rate.  If so, no scaling or compensation need be done.
              thresh_lo = adjust_tsc_khz(tsc_khz, -tsc_tolerance_ppm);
              thresh_hi = adjust_tsc_khz(tsc_khz, tsc_tolerance_ppm);
              if (user_tsc_khz < thresh_lo || user_tsc_khz > thresh_hi) {
                      pr_debug("kvm: requested TSC rate %u falls outside tolerance [%u,%u]\n", user_tsc_khz, thresh_lo, thresh_hi);
                      use_scaling = 1;
      NTP daemon in the guest can correct this difference (NTP can correct upto 500ppm).
      Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
      Message-Id: <20200616114741.GA298183@fuller.cnet>
      Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    • Xiaoyao Li's avatar
      KVM: X86: Fix MSR range of APIC registers in X2APIC mode · bf10bd0b
      Xiaoyao Li authored
      Only MSR address range 0x800 through 0x8ff is architecturally reserved
      and dedicated for accessing APIC registers in x2APIC mode.
      Fixes: 0105d1a5
       ("KVM: x2apic interface to lapic")
      Signed-off-by: default avatarXiaoyao Li <xiaoyao.li@intel.com>
      Message-Id: <20200616073307.16440-1-xiaoyao.li@intel.com>
      Cc: stable@vger.kernel.org
      Reviewed-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
      Reviewed-by: default avatarJim Mattson <jmattson@google.com>
      Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    • Sean Christopherson's avatar
      KVM: VMX: Stop context switching MSR_IA32_UMWAIT_CONTROL · bf09fb6c
      Sean Christopherson authored
      Remove support for context switching between the guest's and host's
      desired UMWAIT_CONTROL.  Propagating the guest's value to hardware isn't
      required for correct functionality, e.g. KVM intercepts reads and writes
      to the MSR, and the latency effects of the settings controlled by the
      MSR are not architecturally visible.
      As a general rule, KVM should not allow the guest to control power
      management settings unless explicitly enabled by userspace, e.g. see
      KVM_CAP_X86_DISABLE_EXITS.  E.g. Intel's SDM explicitly states that C0.2
      can improve the performance of SMT siblings.  A devious guest could
      disable C0.2 so as to improve the performance of their workloads at the
      detriment to workloads running in the host or on other VMs.
      Wholesale removal of UMWAIT_CONTROL context switching also fixes a race
      condition where updates from the host may cause KVM to enter the guest
      with the incorrect value.  Because updates are are propagated to all
      CPUs via IPI (SMP function callback), the value in hardware may be
      stale with respect to the cached value and KVM could enter the guest
      with the wrong value in hardware.  As above, the guest can't observe the
      bad value, but it's a weird and confusing wart in the implementation.
      Removal also fixes the unnecessary usage of VMX's atomic load/store MSR
      lists.  Using the lists is only necessary for MSRs that are required for
      correct functionality immediately upon VM-Enter/VM-Exit, e.g. EFER on
      old hardware, or for MSRs that need to-the-uop precision, e.g. perf
      related MSRs.  For UMWAIT_CONTROL, the effects are only visible in the
      kernel via TPAUSE/delay(), and KVM doesn't do any form of delay in
      vcpu_vmx_run().  Using the atomic lists is undesirable as they are more
      expensive than direct RDMSR/WRMSR.
      Furthermore, even if giving the guest control of the MSR is legitimate,
      e.g. in pass-through scenarios, it's not clear that the benefits would
      outweigh the overhead.  E.g. saving and restoring an MSR across a VMX
      roundtrip costs ~250 cycles, and if the guest diverged from the host
      that cost would be paid on every run of the guest.  In other words, if
      there is a legitimate use case then it should be enabled by a new
      per-VM capability.
      Note, KVM still needs to emulate MSR_IA32_UMWAIT_CONTROL so that it can
      correctly expose other WAITPKG features to the guest, e.g. TPAUSE,
      Fixes: 6e3ba4ab
       ("KVM: vmx: Emulate MSR IA32_UMWAIT_CONTROL")
      Cc: stable@vger.kernel.org
      Cc: Jingqi Liu <jingqi.liu@intel.com>
      Cc: Tao Xu <tao3.xu@intel.com>
      Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
      Message-Id: <20200623005135.10414-1-sean.j.christopherson@intel.com>
      Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
  2. 22 Jun, 2020 4 commits
    • Sean Christopherson's avatar
      KVM: nVMX: Plumb L2 GPA through to PML emulation · 2dbebf7a
      Sean Christopherson authored
      Explicitly pass the L2 GPA to kvm_arch_write_log_dirty(), which for all
      intents and purposes is vmx_write_pml_buffer(), instead of having the
      latter pull the GPA from vmcs.GUEST_PHYSICAL_ADDRESS.  If the dirty bit
      update is the result of KVM emulation (rare for L2), then the GPA in the
      VMCS may be stale and/or hold a completely unrelated GPA.
      Fixes: c5f983f6
       ("nVMX: Implement emulated Page Modification Logging")
      Cc: stable@vger.kernel.org
      Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
      Message-Id: <20200622215832.22090-2-sean.j.christopherson@intel.com>
      Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    • Vitaly Kuznetsov's avatar
      KVM: x86/mmu: Avoid mixing gpa_t with gfn_t in walk_addr_generic() · 312d16c7
      Vitaly Kuznetsov authored
      translate_gpa() returns a GPA, assigning it to 'real_gfn' seems obviously
      wrong. There is no real issue because both 'gpa_t' and 'gfn_t' are u64 and
      we don't use the value in 'real_gfn' as a GFN, we do
       real_gfn = gpa_to_gfn(real_gfn);
      instead. 'If you see a "buffalo" sign on an elephant's cage, do not trust
      your eyes', but let's fix it for good.
      No functional change intended.
      Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
      Message-Id: <20200622151435.752560-1-vkuznets@redhat.com>
      Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    • Paolo Bonzini's avatar
      KVM: LAPIC: ensure APIC map is up to date on concurrent update requests · 44d52717
      Paolo Bonzini authored
      The following race can cause lost map update events:
               cpu1                            cpu2
                                      apic_map_dirty = true
                                           pass check
                                               if (!kvm->arch.apic_map_dirty)
                                           and in process of updating map
          other calls to
             apic_map_dirty = true         might be too late for affected cpu
                                           apic_map_dirty = false
          bail out on
            if (!kvm->arch.apic_map_dirty)
      To fix it, record the beginning of an update of the APIC map in
      apic_map_dirty.  If another APIC map change switches apic_map_dirty
      back to DIRTY during the update, kvm_recalculate_apic_map should not
      make it CLEAN, and the other caller will go through the slow path.
      Reported-by: default avatarIgor Mammedov <imammedo@redhat.com>
      Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    • Igor Mammedov's avatar
      kvm: lapic: fix broken vcpu hotplug · af28dfac
      Igor Mammedov authored
      Guest fails to online hotplugged CPU with error
        smpboot: do_boot_cpu failed(-1) to wakeup CPU#4
      It's caused by the fact that kvm_apic_set_state(), which used to call
      recalculate_apic_map() unconditionally and pulled hotplugged CPU into
      apic map, is updating map conditionally on state changes.  In this case
      the APIC map is not considered dirty and the is not updated.
      Fix the issue by forcing unconditional update from kvm_apic_set_state(),
      like it used to be.
      Fixes: 4abaffce
       ("KVM: LAPIC: Recalculate apic map in batch")
      Cc: stable@vger.kernel.org
      Signed-off-by: default avatarIgor Mammedov <imammedo@redhat.com>
      Message-Id: <20200622160830.426022-1-imammedo@redhat.com>
      Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
  3. 19 Jun, 2020 2 commits
  4. 18 Jun, 2020 2 commits
    • Linus Torvalds's avatar
      maccess: make get_kernel_nofault() check for minimal type compatibility · 0c389d89
      Linus Torvalds authored
      Now that we've renamed probe_kernel_address() to get_kernel_nofault()
      and made it look and behave more in line with get_user(), some of the
      subtle type behavior differences end up being more obvious and possibly
      When you do
              get_user(val, user_ptr);
      the type of the access comes from the "user_ptr" part, and the above
      basically acts as
              val = *user_ptr;
      by design (except, of course, for the fact that the actual dereference
      is done with a user access).
      Note how in the above case, the type of the end result comes from the
      pointer argument, and then the value is cast to the type of 'val' as
      part of the assignment.
      So the type of the pointer is ultimately the more important type both
      for the access itself.
      But 'get_kernel_nofault()' may now _look_ similar, but it behaves very
      differently.  When you do
              get_kernel_nofault(val, kernel_ptr);
      it behaves like
              val = *(typeof(val) *)kernel_ptr;
      except, of course, for the fact that the actual dereference is done with
      exception handling so that a faulting access is suppressed and returned
      as the error code.
      But note how different the casting behavior of the two superficially
      similar accesses are: one does the actual access in the size of the type
      the pointer points to, while the other does the access in the size of
      the target, and ignores the pointer type entirely.
      Actually changing get_kernel_nofault() to act like get_user() is almost
      certainly the right thing to do eventually, but in the meantime this
      patch adds logit to at least verify that the pointer type is compatible
      with the type of the result.
      In many cases, this involves just casting the pointer to 'void *' to
      make it obvious that the type of the pointer is not the important part.
      It's not how 'get_user()' acts, but at least the behavioral difference
      is now obvious and explicit.
      Cc: Christoph Hellwig <hch@lst.de>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    • Christoph Hellwig's avatar
      maccess: rename probe_kernel_address to get_kernel_nofault · 25f12ae4
      Christoph Hellwig authored
      Better describe what this helper does, and match the naming of
      Also switch the argument order around, so that it acts and looks
      like get_user().
      Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  5. 17 Jun, 2020 3 commits
    • Christoph Hellwig's avatar
    • Jiri Olsa's avatar
      kretprobe: Prevent triggering kretprobe from within kprobe_flush_task · 9b38cc70
      Jiri Olsa authored
      Ziqian reported lockup when adding retprobe on _raw_spin_lock_irqsave.
      My test was also able to trigger lockdep output:
       WARNING: possible recursive locking detected
       5.6.0-rc6+ #6 Not tainted
       sched-messaging/2767 is trying to acquire lock:
       ffffffff9a492798 (&(kretprobe_table_locks[i].lock)){-.-.}, at: kretprobe_hash_lock+0x52/0xa0
       but task is already holding lock:
       ffffffff9a491a18 (&(kretprobe_table_locks[i].lock)){-.-.}, at: kretprobe_trampoline+0x0/0x50
       other info that might help us debug this:
        Possible unsafe locking scenario:
        *** DEADLOCK ***
        May be due to missing lock nesting notation
       1 lock held by sched-messaging/2767:
        #0: ffffffff9a491a18 (&(kretprobe_table_locks[i].lock)){-.-.}, at: kretprobe_trampoline+0x0/0x50
       stack backtrace:
       CPU: 3 PID: 2767 Comm: sched-messaging Not tainted 5.6.0-rc6+ #6
       Call Trace:
        ? native_queued_spin_lock_slowpath+0x42b/0x9e0
        ? lockdep_hardirqs_on+0x590/0x590
        ? __lock_acquire+0xf63/0x4030
        ? kretprobe_hash_lock+0x52/0xa0
        ? kretprobe_hash_lock+0x52/0xa0
        ? kprobe_fault_handler+0x380/0x380
        ? find_held_lock+0x3a/0x1c0
        ? lock_acquired+0x392/0xbc0
        ? _raw_spin_lock_irqsave+0x50/0x70
        ? __get_valid_kprobe+0x1f0/0x1f0
        ? _raw_spin_unlock_irqrestore+0x3b/0x40
        ? finish_task_switch+0x4b9/0x6d0
        ? __switch_to_asm+0x34/0x70
        ? __switch_to_asm+0x40/0x70
      The code within the kretprobe handler checks for probe reentrancy,
      so we won't trigger any _raw_spin_lock_irqsave probe in there.
      The problem is in outside kprobe_flush_task, where we call:
      where _raw_spin_lock_irqsave triggers the kretprobe and installs
      kretprobe_trampoline handler on _raw_spin_lock_irqsave return.
      The kretprobe_trampoline handler is then executed with already
      locked kretprobe_table_locks, and first thing it does is to
      lock kretprobe_table_locks ;-) the whole lockup path like:
              _raw_spin_lock_irqsave ---> probe triggered, kretprobe_trampoline installed
              ---> kretprobe_table_locks locked
                  kretprobe_hash_lock(current, &head, &flags);  <--- deadlock
      Adding kprobe_busy_begin/end helpers that mark code with fake
      probe installed to prevent triggering of another kprobe within
      this code.
      Using these helpers in kprobe_flush_task, so the probe recursion
      protection check is hit and the probe is never set to prevent
      above lockup.
      Link: http://lkml.kernel.org/r/158927059835.27680.7011202830041561604.stgit@devnote2
      Fixes: ef53d9c5
       ("kprobes: improve kretprobe scalability with hashed locking")
      Cc: Ingo Molnar <mingo@kernel.org>
      Cc: "Gustavo A . R . Silva" <gustavoars@kernel.org>
      Cc: Anders Roxell <anders.roxell@linaro.org>
      Cc: "Naveen N . Rao" <naveen.n.rao@linux.ibm.com>
      Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
      Cc: David Miller <davem@davemloft.net>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: stable@vger.kernel.org
      Reported-by: default avatar"Ziqian SUN (Zamir)" <zsun@redhat.com>
      Acked-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
      Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
      Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
    • Arvind Sankar's avatar
      x86/purgatory: Add -fno-stack-protector · ff58155c
      Arvind Sankar authored
      The purgatory Makefile removes -fstack-protector options if they were
      configured in, but does not currently add -fno-stack-protector.
      If gcc was configured with the --enable-default-ssp configure option,
      this results in the stack protector still being enabled for the
      purgatory (absent distro-specific specs files that might disable it
      again for freestanding compilations), if the main kernel is being
      compiled with stack protection enabled (if it's disabled for the main
      kernel, the top-level Makefile will add -fno-stack-protector).
      This will break the build since commit
       ("x86/purgatory: Fail the build if purgatory.ro has missing symbols")
      and prior to that would have caused runtime failure when trying to use
      Explicitly add -fno-stack-protector to avoid this, as done in other
      Makefiles that need to disable the stack protector.
      Reported-by: default avatarGabriel C <nix.or.die@googlemail.com>
      Signed-off-by: default avatarArvind Sankar <nivedita@alum.mit.edu>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  6. 15 Jun, 2020 2 commits
    • Sean Christopherson's avatar
      KVM: VMX: Add helpers to identify interrupt type from intr_info · 88c200d9
      Sean Christopherson authored
      Add is_intr_type() and is_intr_type_n() to consolidate the boilerplate
      code for querying a specific type of interrupt given an encoded value
      from VMCS.VM_{ENTER,EXIT}_INTR_INFO, with and without an associated
      vector respectively.
      Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
      Message-Id: <20200609014518.26756-1-sean.j.christopherson@intel.com>
      Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    • Qian Cai's avatar
      kvm/svm: disable KCSAN for svm_vcpu_run() · b95273f1
      Qian Cai authored
      For some reasons, running a simple qemu-kvm command with KCSAN will
      reset AMD hosts. It turns out svm_vcpu_run() could not be instrumented.
      Disable it for now.
       # /usr/libexec/qemu-kvm -name ubuntu-18.04-server-cloudimg -cpu host
      	-smp 2 -m 2G -hda ubuntu-18.04-server-cloudimg.qcow2
      === console output ===
      Kernel 5.6.0-next-20200408+ on an x86_64
      hp-dl385g10-05 login:
      <...host reset...>
      HPE ProLiant System BIOS A40 v1.20 (03/09/2018)
      (C) Copyright 1982-2018 Hewlett Packard Enterprise Development LP
      Early system initialization, please wait...
      Signed-off-by: default avatarQian Cai <cai@lca.pw>
      Message-Id: <20200415153709.1559-1-cai@lca.pw>
      Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
  7. 13 Jun, 2020 1 commit
    • Masahiro Yamada's avatar
      treewide: replace '---help---' in Kconfig files with 'help' · a7f7f624
      Masahiro Yamada authored
      Since commit 84af7a61
       ("checkpatch: kconfig: prefer 'help' over
      '---help---'"), the number of '---help---' has been gradually
      decreasing, but there are still more than 2400 instances.
      This commit finishes the conversion. While I touched the lines,
      I also fixed the indentation.
      There are a variety of indentation styles found.
        a) 4 spaces + '---help---'
        b) 7 spaces + '---help---'
        c) 8 spaces + '---help---'
        d) 1 space + 1 tab + '---help---'
        e) 1 tab + '---help---'    (correct indentation)
        f) 1 tab + 1 space + '---help---'
        g) 1 tab + 2 spaces + '---help---'
      In order to convert all of them to 1 tab + 'help', I ran the
      following commend:
        $ find . -name 'Kconfig*' | xargs sed -i 's/^[[:space:]]*---help---/\thelp/'
      Signed-off-by: default avatarMasahiro Yamada <masahiroy@kernel.org>
  8. 12 Jun, 2020 3 commits
  9. 11 Jun, 2020 19 commits