linux-toradex.git/arch/powerpc/kernel, branch v4.1-rc2

powerpc/powernv: Restore non-volatile CRs after nap

2015-05-01T06:55:11+00:00

Patches 7cba160ad "powernv/cpuidle: Redesign idle states management"
and 77b54e9f2 "powernv/powerpc: Add winkle support for offline cpus"
use non-volatile condition registers (cr2, cr3 and cr4) early in the system
reset interrupt handler (system_reset_pSeries()) before it has been determined
if state loss has occurred. If state loss has not occurred, control returns via
the power7_wakeup_noloss() path which does not restore those condition
registers, leaving them corrupted.

Fix this by restoring the condition registers in the power7_wakeup_noloss()
case.

This is apparent when running a KVM guest on hardware that does not
support winkle or sleep and the guest makes use of secondary threads. In
practice this means Power7 machines, though some early unreleased Power8
machines may also be susceptible.

The secondary CPUs are taken off line before the guest is started and
they call pnv_smp_cpu_kill_self(). This checks support for sleep
states (in this case there is no support) and power7_nap() is called.

When the CPU is woken, power7_nap() returns and because the CPU is
still off line, the main while loop executes again. The sleep states
support test is executed again, but because the tested values cannot
have changed, the compiler has optimized the test away and instead we
rely on the result of the first test, which has been left in cr3
and/or cr4. With the result overwritten, the wrong branch is taken and
power7_winkle() is called on a CPU that does not support it, leading
to it stalling.

Fixes: 7cba160ad789 ("powernv/cpuidle: Redesign idle states management")
Fixes: 77b54e9f213f ("powernv/powerpc: Add winkle support for offline cpus")
[mpe: Massage change log a bit more]
Signed-off-by: Sam Bobroff 
Signed-off-by: Michael Ellerman

powerpc/eeh: Delay probing EEH device during hotplug

2015-05-01T03:52:32+00:00

Commit 1c509148b ("powerpc/eeh: Do probe on pci_dn") probes EEH
devices in early stage, which is reasonable to pSeries platform.
However, it's wrong for PowerNV platform because the PE# isn't
determined until the resources (IO and MMIO) are assigned to
PE in hotplug case. So we have to delay probing EEH devices
for PowerNV platform until the PE# is assigned.

Fixes: ff57b454ddb9 ("powerpc/eeh: Do probe on pci_dn")
Signed-off-by: Gavin Shan 
Signed-off-by: Michael Ellerman

powerpc/eeh: Fix race condition in pcibios_set_pcie_reset_state()

2015-05-01T03:52:09+00:00

When asserting reset in pcibios_set_pcie_reset_state(), the PE
is enforced to (hardware) frozen state in order to drop unexpected
PCI transactions (except PCI config read/write) automatically by
hardware during reset, which would cause recursive EEH error.
However, the (software) frozen state EEH_PE_ISOLATED is missed.
When users get 0xFF from PCI config or MMIO read, EEH_PE_ISOLATED
is set in PE state retrival backend. Unfortunately, nobody (the
reset handler or the EEH recovery functinality in host) will clear
EEH_PE_ISOLATED when the PE has been passed through to guest.

The patch sets and clears EEH_PE_ISOLATED properly during reset
in function pcibios_set_pcie_reset_state() to fix the issue.

Fixes: 28158cd ("Enhance pcibios_set_pcie_reset_state()")
Reported-by: Carol L. Soto 
Signed-off-by: Gavin Shan 
Tested-by: Carol L. Soto 
Signed-off-by: Michael Ellerman

Revert "powerpc/tm: Abort syscalls in active transactions"

2015-04-30T05:24:58+00:00

This reverts commit feba40362b11341bee6d8ed58d54b896abbd9f84.

Although the principle of this change is good, the implementation has a
few issues.

Firstly we can sometimes fail to abort a syscall because r12 may have
been clobbered by C code if we went down the virtual CPU accounting
path, or if syscall tracing was enabled.

Secondly we have decided that it is safer to abort the syscall even
earlier in the syscall entry path, so that we avoid the syscall tracing
path when we are transactional.

So that we have time to thoroughly test those changes we have decided to
revert this for this merge window and will merge the fixed version in
the next window.

NB. Rather than reverting the selftest we just drop tm-syscall from
TEST_PROGS so that it's not run by default.

Fixes: feba40362b11 ("powerpc/tm: Abort syscalls in active transactions")
Signed-off-by: Michael Ellerman

Merge tag 'powerpc-4.1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/mpe/linux

2015-04-26T20:23:15+00:00

Pull powerpc fixes from Michael Ellerman:

 - fix for mm_dec_nr_pmds() from Scott.

 - fixes for oopses seen with KVM + THP from Aneesh.

 - build fixes from Aneesh & Shreyas.

* tag 'powerpc-4.1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/mpe/linux:
  powerpc/mm: Fix build error with CONFIG_PPC_TRANSACTIONAL_MEM disabled
  powerpc/kvm: Fix ppc64_defconfig + PPC_POWERNV=n build error
  powerpc/mm/thp: Return pte address if we find trans_splitting.
  powerpc/mm/thp: Make page table walk safe against thp split/collapse
  KVM: PPC: Remove page table walk helpers
  KVM: PPC: Use READ_ONCE when dereferencing pte_t pointer
  powerpc/hugetlb: Call mm_dec_nr_pmds() in hugetlb_free_pmd_range()

Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

2015-04-26T20:06:22+00:00

Pull second batch of KVM changes from Paolo Bonzini:
 "This mostly includes the PPC changes for 4.1, which this time cover
  Book3S HV only (debugging aids, minor performance improvements and
  some cleanups).  But there are also bug fixes and small cleanups for
  ARM, x86 and s390.

  The task_migration_notifier revert and real fix is still pending
  review, but I'll send it as soon as possible after -rc1"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (29 commits)
  KVM: arm/arm64: check IRQ number on userland injection
  KVM: arm: irqfd: fix value returned by kvm_irq_map_gsi
  KVM: VMX: Preserve host CR4.MCE value while in guest mode.
  KVM: PPC: Book3S HV: Use msgsnd for signalling threads on POWER8
  KVM: PPC: Book3S HV: Translate kvmhv_commence_exit to C
  KVM: PPC: Book3S HV: Streamline guest entry and exit
  KVM: PPC: Book3S HV: Use bitmap of active threads rather than count
  KVM: PPC: Book3S HV: Use decrementer to wake napping threads
  KVM: PPC: Book3S HV: Don't wake thread with no vcpu on guest IPI
  KVM: PPC: Book3S HV: Get rid of vcore nap_count and n_woken
  KVM: PPC: Book3S HV: Move vcore preemption point up into kvmppc_run_vcpu
  KVM: PPC: Book3S HV: Minor cleanups
  KVM: PPC: Book3S HV: Simplify handling of VCPUs that need a VPA update
  KVM: PPC: Book3S HV: Accumulate timing information for real-mode code
  KVM: PPC: Book3S HV: Create debugfs file for each guest's HPT
  KVM: PPC: Book3S HV: Add ICP real mode counters
  KVM: PPC: Book3S HV: Move virtual mode ICP functions to real-mode
  KVM: PPC: Book3S HV: Convert ICS mutex lock to spin lock
  KVM: PPC: Book3S HV: Add guest->host real mode completion counters
  KVM: PPC: Book3S HV: Add helpers for lock/unlock hpte
  ...

KVM: PPC: Book3S HV: Use msgsnd for signalling threads on POWER8

2015-04-21T13:21:34+00:00

This uses msgsnd where possible for signalling other threads within
the same core on POWER8 systems, rather than IPIs through the XICS
interrupt controller.  This includes waking secondary threads to run
the guest, the interrupts generated by the virtual XICS, and the
interrupts to bring the other threads out of the guest when exiting.

Aggregated statistics from debugfs across vcpus for a guest with 32
vcpus, 8 threads/vcore, running on a POWER8, show this before the
change:

 rm_entry:     3387.6ns (228 - 86600, 1008969 samples)
  rm_exit:     4561.5ns (12 - 3477452, 1009402 samples)
  rm_intr:     1660.0ns (12 - 553050, 3600051 samples)

and this after the change:

 rm_entry:     3060.1ns (212 - 65138, 953873 samples)
  rm_exit:     4244.1ns (12 - 9693408, 954331 samples)
  rm_intr:     1342.3ns (12 - 1104718, 3405326 samples)

for a test of booting Fedora 20 big-endian to the login prompt.

The time taken for a H_PROD hcall (which is handled in the host
kernel) went down from about 35 microseconds to about 16 microseconds
with this change.

The noinline added to kvmppc_run_core turned out to be necessary for
good performance, at least with gcc 4.9.2 as packaged with Fedora 21
and a little-endian POWER8 host.

Signed-off-by: Paul Mackerras 
Signed-off-by: Alexander Graf

KVM: PPC: Book3S HV: Use bitmap of active threads rather than count

2015-04-21T13:21:33+00:00

Currently, the entry_exit_count field in the kvmppc_vcore struct
contains two 8-bit counts, one of the threads that have started entering
the guest, and one of the threads that have started exiting the guest.
This changes it to an entry_exit_map field which contains two bitmaps
of 8 bits each.  The advantage of doing this is that it gives us a
bitmap of which threads need to be signalled when exiting the guest.
That means that we no longer need to use the trick of setting the
HDEC to 0 to pull the other threads out of the guest, which led in
some cases to a spurious HDEC interrupt on the next guest entry.

Signed-off-by: Paul Mackerras 
Signed-off-by: Alexander Graf

KVM: PPC: Book3S HV: Get rid of vcore nap_count and n_woken

2015-04-21T13:21:32+00:00

We can tell when a secondary thread has finished running a guest by
the fact that it clears its kvm_hstate.kvm_vcpu pointer, so there
is no real need for the nap_count field in the kvmppc_vcore struct.
This changes kvmppc_wait_for_nap to poll the kvm_hstate.kvm_vcpu
pointers of the secondary threads rather than polling vc->nap_count.
Besides reducing the size of the kvmppc_vcore struct by 8 bytes,
this also means that we can tell which secondary threads have got
stuck and thus print a more informative error message.

Signed-off-by: Paul Mackerras 
Signed-off-by: Alexander Graf

KVM: PPC: Book3S HV: Minor cleanups

2015-04-21T13:21:32+00:00

* Remove unused kvmppc_vcore::n_busy field.
* Remove setting of RMOR, since it was only used on PPC970 and the
  PPC970 KVM support has been removed.
* Don't use r1 or r2 in setting the runlatch since they are
  conventionally reserved for other things; use r0 instead.
* Streamline the code a little and remove the ext_interrupt_to_host
  label.
* Add some comments about register usage.
* hcall_try_real_mode doesn't need to be global, and can't be
  called from C code anyway.

Signed-off-by: Paul Mackerras 
Signed-off-by: Alexander Graf