linux.git/arch/mips/kvm, branch v4.1.29

MIPS: KVM: Fix modular KVM under QEMU

2016-07-11T00:19:56+00:00

[ Upstream commit 797179bc4fe06c89e47a9f36f886f68640b423f8 ]

Copy __kvm_mips_vcpu_run() into unmapped memory, so that we can never
get a TLB refill exception in it when KVM is built as a module.

This was observed to happen with the host MIPS kernel running under
QEMU, due to a not entirely transparent optimisation in the QEMU TLB
handling where TLB entries replaced with TLBWR are copied to a separate
part of the TLB array. Code in those pages continue to be executable,
but those mappings persist only until the next ASID switch, even if they
are marked global.

An ASID switch happens in __kvm_mips_vcpu_run() at exception level after
switching to the guest exception base. Subsequent TLB mapped kernel
instructions just prior to switching to the guest trigger a TLB refill
exception, which enters the guest exception handlers without updating
EPC. This appears as a guest triggered TLB refill on a host kernel
mapped (host KSeg2) address, which is not handled correctly as user
(guest) mode accesses to kernel (host) segments always generate address
error exceptions.

Signed-off-by: James Hogan 
Cc: Paolo Bonzini 
Cc: Radim Krčmář 
Cc: Ralf Baechle 
Cc: kvm@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc:  # 3.10.x-
Signed-off-by: Paolo Bonzini 
Signed-off-by: Sasha Levin

MIPS: KVM: Fix timer IRQ race when writing CP0_Compare

2016-06-06T23:12:16+00:00

[ Upstream commit b45bacd2d048f405c7760e5cc9b60dd67708734f ]

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
Cc:  # 3.16.x-
Signed-off-by: Paolo Bonzini 
Signed-off-by: Sasha Levin

MIPS: KVM: Fix timer IRQ race when freezing timer

2016-06-06T23:12:16+00:00

[ Upstream commit 4355c44f063d3de4f072d796604c7f4ba4085cc3 ]

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
Cc:  # 3.16.x-
Signed-off-by: Paolo Bonzini 
Signed-off-by: Sasha Levin

MIPS: kvm: Fix ioctl error handling.

2016-03-09T18:15:18+00:00

[ Upstream commit 887349f69f37e71e2a8bfbd743831625a0b2ff51 ]

Calling return copy_to_user(...) or return copy_from_user in an ioctl
will 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.

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

everywhere.

Signed-off-by: Michael S. Tsirkin 
Cc: Paolo Bonzini 
Cc: James Hogan 
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: stable@vger.kernel.org
Cc: kvm@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12709/
Signed-off-by: Ralf Baechle 
Signed-off-by: Sasha Levin

MIPS: KVM: Uninit VCPU in vcpu_create error path

2015-12-09T19:03:16+00:00

commit 585bb8f9a5e592f2ce7abbe5ed3112d5438d2754 upstream.

If either of the memory allocations in kvm_arch_vcpu_create() fail, the
vcpu which has been allocated and kvm_vcpu_init'd doesn't get uninit'd
in the error handling path. Add a call to kvm_vcpu_uninit() to fix this.

Fixes: 669e846e6c4e ("KVM/MIPS32: MIPS arch specific APIs for KVM")
Signed-off-by: James Hogan 
Cc: Ralf Baechle 
Cc: Paolo Bonzini 
Cc: Gleb Natapov 
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 CACHE immediate offset sign extension

2015-12-09T19:03:16+00:00

commit c5c2a3b998f1ff5a586f9d37e154070b8d550d17 upstream.

The immediate field of the CACHE instruction is signed, so ensure that
it gets sign extended by casting it to an int16_t rather than just
masking the low 16 bits.

Fixes: e685c689f3a8 ("KVM/MIPS32: Privileged instruction/target branch emulation.")
Signed-off-by: James Hogan 
Cc: Ralf Baechle 
Cc: Paolo Bonzini 
Cc: Gleb Natapov 
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 ASID restoration logic

2015-12-09T19:03:15+00:00

commit 002374f371bd02df864cce1fe85d90dc5b292837 upstream.

ASID restoration on guest resume should determine the guest execution
mode based on the guest Status register rather than bit 30 of the guest
PC.

Fix the two places in locore.S that do this, loading the guest status
from the cop0 area. Note, this assembly is specific to the trap &
emulate implementation of KVM, so it doesn't need to check the
supervisor bit as that mode is not implemented in the guest.

Fixes: b680f70fc111 ("KVM/MIPS32: Entry point for trampolining to...")
Signed-off-by: James Hogan 
Cc: Ralf Baechle 
Cc: Paolo Bonzini 
Cc: Gleb Natapov 
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Signed-off-by: Paolo Bonzini 
Signed-off-by: Greg Kroah-Hartman

KVM: mips: use id_to_memslot correctly

2015-07-10T16:49:36+00:00

commit 69a1220060c1523fd0515216eaa29e22f133b894 upstream.

The argument to KVM_GET_DIRTY_LOG is a memslot id; it may not match the
position in the memslots array, which is sorted by gfn.

Reviewed-by: James Hogan 
Signed-off-by: Paolo Bonzini 
Signed-off-by: Greg Kroah-Hartman

MIPS: KVM: Do not sign extend on unsigned MMIO load

2015-06-06T08:21:10+00:00

Fix possible unintended sign extension in unsigned MMIO loads by casting
to uint16_t in the case of mmio_needed != 2.

Signed-off-by: Nicholas Mc Guire 
Reviewed-by: James Hogan 
Tested-by: James Hogan 
Cc: Gleb Natapov 
Cc: Paolo Bonzini 
Cc: kvm@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/9985/
Signed-off-by: Ralf Baechle

MIPS: KVM: Fix unused variable build warning

2015-05-12T21:53:56+00:00

As kvm_mips_complete_mmio_load() did not yet modify PC at this point
as James Hogans  explained the curr_pc variable
and the comments along with it can be dropped.

Signed-off-by: Nicholas Mc Guire 
Link: http://lkml.org/lkml/2015/5/8/422
Cc: Gleb Natapov 
Cc: Paolo Bonzini 
Cc: James Hogan 
Cc: kvm@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/9993/
Signed-off-by: Ralf Baechle