linux-stable.git/arch/mips/kvm, branch linux-4.5.y

MIPS: KVM: Fix timer IRQ race when writing CP0_Compare

2016-06-01T19:17:01+00:00

commit b45bacd2d048f405c7760e5cc9b60dd67708734f upstream.

Writing CP0_Compare clears the timer interrupt pending bit
(CP0_Cause.TI), but this wasn't being done atomically. If a timer
interrupt raced with the write of the guest CP0_Compare, the timer
interrupt could end up being pending even though the new CP0_Compare is
nowhere near CP0_Count.

We were already updating the hrtimer expiry with
kvm_mips_update_hrtimer(), which used both kvm_mips_freeze_hrtimer() and
kvm_mips_resume_hrtimer(). Close the race window by expanding out
kvm_mips_update_hrtimer(), and clearing CP0_Cause.TI and setting
CP0_Compare between the freeze and resume. Since the pending timer
interrupt should not be cleared when CP0_Compare is written via the KVM
user API, an ack argument is added to distinguish the source of the
write.

Fixes: e30492bbe95a ("MIPS: KVM: Rewrite count/compare timer emulation")
Signed-off-by: James Hogan 
Cc: Paolo Bonzini 
Cc: "Radim KrÄmÃ¡Å™" 
Cc: Ralf Baechle 
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Signed-off-by: Paolo Bonzini 
Signed-off-by: Greg Kroah-Hartman

MIPS: KVM: Fix timer IRQ race when freezing timer

2016-06-01T19:17:01+00:00

commit 4355c44f063d3de4f072d796604c7f4ba4085cc3 upstream.

There's a particularly narrow and subtle race condition when the
software emulated guest timer is frozen which can allow a guest timer
interrupt to be missed.

This happens due to the hrtimer expiry being inexact, so very
occasionally the freeze time will be after the moment when the emulated
CP0_Count transitions to the same value as CP0_Compare (so an IRQ should
be generated), but before the moment when the hrtimer is due to expire
(so no IRQ is generated). The IRQ won't be generated when the timer is
resumed either, since the resume CP0_Count will already match CP0_Compare.

With VZ guests in particular this is far more likely to happen, since
the soft timer may be frozen frequently in order to restore the timer
state to the hardware guest timer. This happens after 5-10 hours of
guest soak testing, resulting in an overflow in guest kernel timekeeping
calculations, hanging the guest. A more focussed test case to
intentionally hit the race (with the help of a new hypcall to cause the
timer state to migrated between hardware & software) hits the condition
fairly reliably within around 30 seconds.

Instead of relying purely on the inexact hrtimer expiry to determine
whether an IRQ should be generated, read the guest CP0_Compare and
directly check whether the freeze time is before or after it. Only if
CP0_Count is on or after CP0_Compare do we check the hrtimer expiry to
determine whether the last IRQ has already been generated (which will
have pushed back the expiry by one timer period).

Fixes: e30492bbe95a ("MIPS: KVM: Rewrite count/compare timer emulation")
Signed-off-by: James Hogan 
Cc: Paolo Bonzini 
Cc: "Radim KrÄmÃ¡Å™" 
Cc: Ralf Baechle 
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Signed-off-by: Paolo Bonzini 
Signed-off-by: Greg Kroah-Hartman

mips/kvm: fix ioctl error handling

2016-03-02T09:34:52+00:00

Returning directly whatever copy_to_user(...) or copy_from_user(...)
returns may not do the right thing if there's a pagefault:
copy_to_user/copy_from_user return the number of bytes not copied in
this case, but ioctls need to return -EFAULT instead.

Fix up kvm on mips to do
	return copy_to_user(...)) ?  -EFAULT : 0;
and
	return copy_from_user(...)) ?  -EFAULT : 0;

everywhere.

Cc: stable@vger.kernel.org
Signed-off-by: Michael S. Tsirkin 
Signed-off-by: Paolo Bonzini

Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus

2016-01-24T20:50:56+00:00

Pull MIPS updates from Ralf Baechle:
 "This is the main pull request for MIPS for 4.5 plus some 4.4 fixes.

  The executive summary:

   - ATH79 platform improvments, use DT bindings for the ATH79 USB PHY.
   - Avoid useless rebuilds for zboot.
   - jz4780: Add NEMC, BCH and NAND device tree nodes
   - Initial support for the MicroChip's DT platform.  As all the device
     drivers are missing this is still of limited use.
   - Some Loongson3 cleanups.
   - The unavoidable whitespace polishing.
   - Reduce clock skew when synchronizing the CPU cycle counters on CPU
     startup.
   - Add MIPS R6 fixes.
   - Lots of cleanups across arch/mips as fallout from KVM.
   - Lots of minor fixes and changes for IEEE 754-2008 support to the
     FPU emulator / fp-assist software.
   - Minor Ralink, BCM47xx and bcm963xx platform support improvments.
   - Support SMP on BCM63168"

* 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus: (84 commits)
  MIPS: zboot: Add support for serial debug using the PROM
  MIPS: zboot: Avoid useless rebuilds
  MIPS: BMIPS: Enable ARCH_WANT_OPTIONAL_GPIOLIB
  MIPS: bcm63xx: nvram: Remove unused bcm63xx_nvram_get_psi_size() function
  MIPS: bcm963xx: Update bcm_tag field image_sequence
  MIPS: bcm963xx: Move extended flash address to bcm_tag header file
  MIPS: bcm963xx: Move Broadcom BCM963xx image tag data structure
  MIPS: bcm63xx: nvram: Use nvram structure definition from header file
  MIPS: bcm963xx: Add Broadcom BCM963xx board nvram data structure
  MAINTAINERS: Add KVM for MIPS entry
  MIPS: KVM: Add missing newline to kvm_err()
  MIPS: Move KVM specific opcodes into asm/inst.h
  MIPS: KVM: Use cacheops.h definitions
  MIPS: Break down cacheops.h definitions
  MIPS: Use EXCCODE_ constants with set_except_vector()
  MIPS: Update trap codes
  MIPS: Move Cause.ExcCode trap codes to mipsregs.h
  MIPS: KVM: Make kvm_mips_{init,exit}() static
  MIPS: KVM: Refactor added offsetof()s
  MIPS: KVM: Convert EXPORT_SYMBOL to _GPL
  ...

MIPS: KVM: Add missing newline to kvm_err()

2016-01-24T02:38:48+00:00

Add missing newline to end of kvm_err string when guest PMAP couldn't be
allocated.

Signed-off-by: James Hogan 
Cc: Gleb Natapov 
Cc: Paolo Bonzini 
Cc: kvm@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/11896/
Signed-off-by: Ralf Baechle

MIPS: Move KVM specific opcodes into asm/inst.h

2016-01-24T02:31:17+00:00

The header arch/mips/kvm/opcode.h defines a few extra opcodes which
aren't in arch/mips/include/uapi/asm/inst.h. There's nothing KVM
specific about them, so lets move them into inst.h where they belong and
delete the header.

Note that mfmcz_op is renamed to mfmc0_op to match the instruction set
manual, and wait_op was already added to inst.h in commit b0a3eae2b943
("MIPS: inst.h: define COP0 wait op"), merged in v3.16-rc1.

Signed-off-by: James Hogan 
Cc: Paolo Bonzini 
Cc: Gleb Natapov 
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/11895/
Signed-off-by: Ralf Baechle

MIPS: KVM: Use cacheops.h definitions

2016-01-24T02:30:41+00:00

Drop the custom cache operation code definitions used by KVM for
emulating guest CACHE instructions, and switch to use the existing
definitions in .

Signed-off-by: James Hogan 
Cc: Paolo Bonzini 
Cc: Gleb Natapov 
Cc: kvm@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/11893/
Signed-off-by: Ralf Baechle

MIPS: Move Cause.ExcCode trap codes to mipsregs.h

2016-01-24T02:15:51+00:00

Move the Cause.ExcCode trap code definitions from kvm_host.h to
mipsregs.h, since they describe architectural bits rather than KVM
specific constants, and change the prefix from T_ to EXCCODE_.

Signed-off-by: James Hogan 
Cc: Paolo Bonzini 
Cc: Gleb Natapov 
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/11891/
Signed-off-by: Ralf Baechle

MIPS: KVM: Make kvm_mips_{init,exit}() static

2016-01-24T02:15:01+00:00

The module init and exit functions have no need to be global, so make
them static.

Signed-off-by: James Hogan 
Cc: Paolo Bonzini 
Cc: Gleb Natapov 
Cc: kvm@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/11889/
Signed-off-by: Ralf Baechle

MIPS: KVM: Refactor added offsetof()s

2016-01-24T02:14:15+00:00

When calculating the offsets into the commpage for dynamically
translated mtc0/mfc0 guest instructions, multiple offsetof()s are added
together to find the offset of the specific register in the mips_coproc,
within the commpage.

Simplify each of these cases to a single offsetof() to find the offset
of the specific register within the commpage.

Signed-off-by: James Hogan 
Cc: Paolo Bonzini 
Cc: Gleb Natapov 
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/11888/
Signed-off-by: Ralf Baechle