Of slab shrinkers, the VM code says:

 * Note that 'shrink' will be passed nr_to_scan == 0 when the VM is
 * querying the cache size, so a fastpath for that case is appropriate.

and it *means* it.  Look at how it calls the shrinkers:

    nr_before = (*shrinker->shrink)(0, gfp_mask);
    shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);

So, if you do anything stupid in your shrinker, the VM will doubly
punish you.

The mmu_shrink() function takes the global kvm_lock, then acquires
every VM's kvm->mmu_lock in sequence.  If we have 100 VMs, then
we're going to take 101 locks.  We do it twice, so each call takes
202 locks.  If we're under memory pressure, we can have each cpu
trying to do this.  It can get really hairy, and we've seen lock
spinning in mmu_shrink() be the dominant entry in profiles.

This is guaranteed to optimize at least half of those lock
aquisitions away.  It removes the need to take any of the locks
when simply trying to count objects.

A 'percpu_counter' can be a large object, but we only have one
of these for the entire system.  There are not any better
alternatives at the moment, especially ones that handle CPU
hotplug.
Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Tim Pepper <lnxninja@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

Doing this makes the code much more readable.  That's
borne out by the fact that this patch removes code.  "used"
also happens to be the number that we need to return back to
the slab code when our shrinker gets called.  Keeping this
value as opposed to free makes the next patch simpler.

So, 'struct kvm' is kzalloc()'d.  'struct kvm_arch' is a
structure member (and not a pointer) of 'struct kvm'.  That
means they start out zeroed.  I _think_ they get initialized
properly by kvm_mmu_change_mmu_pages().  But, that only happens
via kvm ioctls.

Another benefit of storing 'used' intead of 'free' is
that the values are consistent from the moment the structure is
allocated: no negative "used" value.
Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Tim Pepper <lnxninja@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch.n_alloc_mmu_pages is a poor choice of name. This value truly
means, "the number of pages which _may_ be allocated".  But,
reading the name, "n_alloc_mmu_pages" implies "the number of allocated
mmu pages", which is dead wrong.

It's really the high watermark, so let's give it a name to match:
nr_max_mmu_pages.  This change will make the next few patches
much more obvious and easy to read.
Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Tim Pepper <lnxninja@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

"free" is a poor name for this value.  In this context, it means,
"the number of mmu pages which this kvm instance should be able to
allocate."  But "free" implies much more that the objects are there
and ready for use.  "available" is a much better description, especially
when you see how it is calculated.

In this patch, we abstract its use into a function.  We'll soon
replace the function's contents by calculating the value in a
different way.

All of the reads of n_free_mmu_pages are taken care of in this
patch.  The modification sites will be handled in a patch
later in the series.
Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Tim Pepper <lnxninja@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

Signed-off-by: Avi Kivity <avi@redhat.com>

Signed-off-by: Avi Kivity <avi@redhat.com>

Needed for 3-operand IMUL.
Signed-off-by: Avi Kivity <avi@redhat.com>

Signed-off-by: Avi Kivity <avi@redhat.com>

Signed-off-by: Avi Kivity <avi@redhat.com>

Useless.
Signed-off-by: Avi Kivity <avi@redhat.com>

Signed-off-by: Avi Kivity <avi@redhat.com>

Signed-off-by: Avi Kivity <avi@redhat.com>

Signed-off-by: Avi Kivity <avi@redhat.com>

Used for RET NEAR instructions.
Signed-off-by: Avi Kivity <avi@redhat.com>

Signed-off-by: Avi Kivity <avi@redhat.com>

Signed-off-by: Avi Kivity <avi@redhat.com>

Most x86 two operand instructions allow the destination to be a memory operand,
but IMUL (for example) requires that the destination be a register.  Change
____emulate_2op() to take a register for both source and destination so we
can invoke IMUL.
Signed-off-by: Avi Kivity <avi@redhat.com>

We'll need it later so we can use a register for the destination.
Signed-off-by: Avi Kivity <avi@redhat.com>

Add LOOP/LOOPcc instruction emulation (opcode 0xe0~0xe2).
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

Add CBW/CWDE/CDQE instruction emulation.(opcode 0x98)
Used by FreeBSD's boot loader.
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

EFLAGS.ZF needs to be checked after each iteration, not before.
Signed-off-by: Avi Kivity <avi@redhat.com>

Signed-off-by: Avi Kivity <avi@redhat.com>

emulate_push() only schedules a push; it doesn't actually push anything.
Call writeback() to flush out the write.
Signed-off-by: Avi Kivity <avi@redhat.com>

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

Change OUT instruction to use dst instead of src, so we can
reuse those code for all out instructions.
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

Introduce DstImmUByte for dst operand decode, which
will be used for out instruction.
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

Add setcc instruction emulation (opcode 0x0f 0x90~0x9f)
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

no-kvmclock kernel parameter is missing its explanation in
Documentation/kernel-parameters.txt. Add it.
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Avi Kivity <avi@redhat.com>

Add XADD instruction emulation (opcode 0x0f 0xc0~0xc1)
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

Introduce function write_register_operand() to write back the
register operand.
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

Add kvm_release_page_clean() after is_error_page() to avoid
leakage of error page.
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

The code for initializing the emulation context is duplicated at two
locations (emulate_instruction() and kvm_task_switch()). Separate it
in a separate function and call it from there.
Signed-off-by: Mohammed Gamal <m.gamal005@gmail.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

Add bsf/bsr instruction emulation (opcode 0x0f 0xbc~0xbd)
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

This patch lets emulate_grp3() return X86EMUL_* return codes instead
of hardcoded ones.
Signed-off-by: Mohammed Gamal <m.gamal005@gmail.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

This adds unary mul, imul, div, and idiv instructions (group 3 r/m 4-7).
Signed-off-by: Mohammed Gamal <m.gamal005@gmail.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

Mask group 8 instruction as BitOp, so we can share the
code for adjust the source operand.
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

adjust the dst address for a register source but not adjust the
address for an immediate source.
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

If bit offset operands is a negative number, BitOp instruction
will return wrong value. This patch fix it.
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

Signed-off-by: Mohammed Gamal <m.gamal005@gmail.com>
Signed-off-by: Avi Kivity <avi@redhat.com>