Commit graph

103 commits

Author SHA1 Message Date
Izik Eidus
b4231d6180 KVM: MMU: Selectively set PageDirty when releasing guest memory
Improve dirty bit setting for pages that kvm release, until now every page
that we released we marked dirty, from now only pages that have potential
to get dirty we mark dirty.

Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30 17:53:09 +02:00
Izik Eidus
2065b3727e KVM: MMU: Fix potential memory leak with smp real-mode
When we map a page, we check whether some other vcpu mapped it for us and if
so, bail out.  But we should decrease the refcount on the page as we do so.

Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30 17:53:08 +02:00
Avi Kivity
4cee576493 KVM: MMU: Add some mmu statistics
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30 17:53:04 +02:00
Avi Kivity
b733bfb524 KVM: MMU: Topup the mmu memory preallocation caches before emulating an insn
Emulation may cause a shadow pte to be instantiated, which requires
memory resources.  Make sure the caches are filled to avoid an oops.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30 17:52:57 +02:00
Avi Kivity
3067714cf5 KVM: Move page fault processing to common code
The code that dispatches the page fault and emulates if we failed to map
is duplicated across vmx and svm.  Merge it to simplify further bugfixing.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30 17:52:57 +02:00
Zhang Xiantao
34c16eecf7 KVM: Portability: Split kvm_vcpu into arch dependent and independent parts (part 1)
First step to split kvm_vcpu.  Currently, we just use an macro to define
the common fields in kvm_vcpu for all archs, and all archs need to define
its own kvm_vcpu struct.

Signed-off-by: Zhang Xiantao <xiantao.zhang@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30 17:52:54 +02:00
Izik Eidus
8a7ae055f3 KVM: MMU: Partial swapping of guest memory
This allows guest memory to be swapped.  Pages which are currently mapped
via shadow page tables are pinned into memory, but all other pages can
be freely swapped.

The patch makes gfn_to_page() elevate the page's reference count, and
introduces kvm_release_page() that pairs with it.

Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30 17:52:54 +02:00
Izik Eidus
cea7bb2128 KVM: MMU: Make gfn_to_page() always safe
In case the page is not present in the guest memory map, return a dummy
page the guest can scribble on.

This simplifies error checking in its users.

Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30 17:52:54 +02:00
Izik Eidus
9647c14c98 KVM: MMU: Keep a reverse mapping of non-writable translations
The current kvm mmu only reverse maps writable translation.  This is used
to write-protect a page in case it becomes a pagetable.

But with swapping support, we need a reverse mapping of read-only pages as
well:  when we evict a page, we need to remove any mapping to it, whether
writable or not.

Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30 17:52:54 +02:00
Izik Eidus
98348e9507 KVM: MMU: Add rmap_next(), a helper for walking kvm rmaps
Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30 17:52:54 +02:00
Avi Kivity
6bfccdc9ae KVM: MMU: Instantiate real-mode shadows as user writable shadows
This is consistent with real-mode permissions.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30 17:52:52 +02:00
Avi Kivity
e3c5e7ec9e KVM: Move guest pte dirty bit management to the guest pagetable walker
This is more consistent with the accessed bit management, and makes the dirty
bit available earlier for other purposes.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30 17:52:51 +02:00
Anthony Liguori
4a4c992487 KVM: MMU: More struct kvm_vcpu -> struct kvm cleanups
This time, the biggest change is gpa_to_hpa. The translation of GPA to HPA does
not depend on the VCPU state unlike GVA to GPA so there's no need to pass in
the kvm_vcpu.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30 17:52:51 +02:00
Anthony Liguori
f67a46f4aa KVM: MMU: Clean up MMU functions to take struct kvm when appropriate
Some of the MMU functions take a struct kvm_vcpu even though they affect all
VCPUs.  This patch cleans up some of them to instead take a struct kvm.  This
makes things a bit more clear.

The main thing that was confusing me was whether certain functions need to be
called on all VCPUs.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30 17:52:51 +02:00
Mike Day
d77c26fce9 KVM: CodingStyle cleanup
Signed-off-by: Mike D. Day <ncmike@ncultra.org>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30 17:52:50 +02:00
Izik Eidus
82ce2c9683 KVM: Allow dynamic allocation of the mmu shadow cache size
The user is now able to set how many mmu pages will be allocated to the guest.

Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30 17:52:50 +02:00
Izik Eidus
290fc38da8 KVM: Remove the usage of page->private field by rmap
When kvm uses user-allocated pages in the future for the guest, we won't
be able to use page->private for rmap, since page->rmap is reserved for
the filesystem.  So we move the rmap base pointers to the memory slot.

A side effect of this is that we need to store the gfn of each gpte in
the shadow pages, since the memory slot is addressed by gfn, instead of
hfn like struct page.

Signed-off-by: Izik Eidus <izik@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30 17:52:50 +02:00
Avi Kivity
12b7d28fc1 KVM: MMU: Make flooding detection work when guest page faults are bypassed
When we allow guest page faults to reach the guests directly, we lose
the fault tracking which allows us to detect demand paging.  So we provide
an alternate mechnism by clearing the accessed bit when we set a pte, and
checking it later to see if the guest actually used it.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30 17:52:48 +02:00
Avi Kivity
c7addb9020 KVM: Allow not-present guest page faults to bypass kvm
There are two classes of page faults trapped by kvm:
 - host page faults, where the fault is needed to allow kvm to install
   the shadow pte or update the guest accessed and dirty bits
 - guest page faults, where the guest has faulted and kvm simply injects
   the fault back into the guest to handle

The second class, guest page faults, is pure overhead.  We can eliminate
some of it on vmx using the following evil trick:
 - when we set up a shadow page table entry, if the corresponding guest pte
   is not present, set up the shadow pte as not present
 - if the guest pte _is_ present, mark the shadow pte as present but also
   set one of the reserved bits in the shadow pte
 - tell the vmx hardware not to trap faults which have the present bit clear

With this, normal page-not-present faults go directly to the guest,
bypassing kvm entirely.

Unfortunately, this trick only works on Intel hardware, as AMD lacks a
way to discriminate among page faults based on error code.  It is also
a little risky since it uses reserved bits which might become unreserved
in the future, so a module parameter is provided to disable it.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30 17:52:48 +02:00
Eddie Dong
8668a3c468 KVM: VMX: Reset mmu context when entering real mode
Resetting an SMP guest will force AP enter real mode (RESET) with
paging enabled in protected mode. While current enter_rmode() can
only handle mode switch from nonpaging mode to real mode which leads
to SMP reboot failure.

Fix by reloading the mmu context on entering real mode.

Signed-off-by: Yaozu (Eddie) Dong <eddie.dong@intel.com>
Signed-off-by: Qing He <qing.he@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-10-22 12:03:28 +02:00
Izik Eidus
7f2145ad6f KVM: MMU: Set shadow pte atomically in mmu_pte_write_zap_pte()
Setting shadow page table entry should be set atomicly using set_shadow_pte().

Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-10-22 12:03:28 +02:00
Avi Kivity
2e3e5882dc KVM: MMU: Don't do GFP_NOWAIT allocations
Before preempt notifiers, kvm needed to allocate memory with GFP_NOWAIT so
as not to have to enable preemption and take a heavyweight exit.  On oom, we'd
fall back to a GFP_KERNEL allocation.

With preemption notifiers, we can do a GFP_KERNEL allocation, and perform
the heavyweight exit only if the kernel decides to put us to sleep.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-10-13 10:18:27 +02:00
Christian Ehrhardt
cbdd1bea2a KVM: Rename kvm_arch_ops to kvm_x86_ops
This patch just renames the current (misnamed) _arch namings to _x86 to
ensure better readability when a real arch layer takes place.

Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-10-13 10:18:27 +02:00
Shaohua Li
11ec280471 KVM: Convert vm lock to a mutex
This allows the kvm mmu to perform sleepy operations, such as memory
allocation.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-10-13 10:18:20 +02:00
Avi Kivity
15ad71460d KVM: Use the scheduler preemption notifiers to make kvm preemptible
Current kvm disables preemption while the new virtualization registers are
in use.  This of course is not very good for latency sensitive workloads (one
use of virtualization is to offload user interface and other latency
insensitive stuff to a container, so that it is easier to analyze the
remaining workload).  This patch re-enables preemption for kvm; preemption
is now only disabled when switching the registers in and out, and during
the switch to guest mode and back.

Contains fixes from Shaohua Li <shaohua.li@intel.com>.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-10-13 10:18:20 +02:00
Shaohua Li
fe55188194 KVM: Move gfn_to_page out of kmap/unmap pairs
gfn_to_page might sleep with swap support. Move it out of the kmap calls.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-10-13 10:18:19 +02:00
Rusty Russell
707d92fa72 KVM: Trivial: Use standard CR0 flags macros from asm/cpu-features.h
The kernel now has asm/cpu-features.h: use those macros instead of
inventing our own.

Also spell out definition of CR0_RESEVED_BITS (no code change) and fix typo.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-10-13 10:18:18 +02:00
Avi Kivity
22d95b1282 KVM: MMU: Fix rare oops on guest context switch
A guest context switch to an uncached cr3 can require allocation of
shadow pages, but we only recycle shadow pages in kvm_mmu_page_fault().

Move shadow page recycling to mmu_topup_memory_caches(), which is called
from both the page fault handler and from guest cr3 reload.

Signed-off-by: Avi Kivity <avi@qumranet.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-09-14 13:59:55 -07:00
Avi Kivity
c4d198d518 KVM: MMU: Fix cleaning up the shadow page allocation cache
__free_page() wants a struct page, not a virtual address.

Signed-off-by: Avi Kivity <avi@qumranet.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-20 23:48:47 -07:00
Avi Kivity
c1158e63df KVM: MMU: Fix oopses with SLUB
The kvm mmu uses page->private on shadow page tables; so does slub, and
an oops result.  Fix by allocating regular pages for shadows instead of
using slub.

Tested-by: S.Çağlar Onur <caglar@pardus.org.tr>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-20 20:23:59 +03:00
Avi Kivity
90cb0529dd KVM: Fix memory slot management functions for guest smp
The memory slot management functions were oriented against vcpu 0, where
they should be kvm-wide.  This causes hangs starting X on guest smp.

Fix by making the functions (and resultant tail in the mmu) non-vcpu-specific.
Unfortunately this reduces the efficiency of the mmu object cache a bit.  We
may have to revisit this later.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-20 20:16:29 +03:00
Paul Mundt
20c2df83d2 mm: Remove slab destructors from kmem_cache_create().
Slab destructors were no longer supported after Christoph's
c59def9f22 change. They've been
BUGs for both slab and slub, and slob never supported them
either.

This rips out support for the dtor pointer from kmem_cache_create()
completely and fixes up every single callsite in the kernel (there were
about 224, not including the slab allocator definitions themselves,
or the documentation references).

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
2007-07-20 10:11:58 +09:00
Avi Kivity
e495606dd0 KVM: Clean up #includes
Remove unnecessary ones, and rearange the remaining in the standard order.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16 12:05:49 +03:00
Shaohua Li
88a97f0b2f KVM: MMU: Fix Wrong tlb flush order
Need to flush the tlb after updating a pte, not before.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16 12:05:48 +03:00
Avi Kivity
d9e368d612 KVM: Flush remote tlbs when reducing shadow pte permissions
When a vcpu causes a shadow tlb entry to have reduced permissions, it
must also clear the tlb on remote vcpus.  We do that by:

- setting a bit on the vcpu that requests a tlb flush before the next entry
- if the vcpu is currently executing, we send an ipi to make sure it
  exits before we continue

Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16 12:05:46 +03:00
Avi Kivity
7b53aa5650 KVM: Fix vcpu freeing for guest smp
A vcpu can pin up to four mmu shadow pages, which means the freeing
loop will never terminate.  Fix by first unpinning shadow pages on
all vcpus, then freeing shadow pages.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16 12:05:45 +03:00
Avi Kivity
17c3ba9d37 KVM: Lazy guest cr3 switching
Switch guest paging context may require us to allocate memory, which
might fail.  Instead of wiring up error paths everywhere, make context
switching lazy and actually do the switch before the next guest entry,
where we can return an error if allocation fails.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16 12:05:45 +03:00
Avi Kivity
bd2b2baa5c KVM: MMU: Remove unused large page marker
This has not been used for some time, as the same information is available
in the page header.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16 12:05:45 +03:00
Avi Kivity
b64b3763a5 KVM: MMU: Don't cache guest access bits in the shadow page table
This was once used to avoid accessing the guest pte when upgrading
the shadow pte from read-only to read-write.  But usually we need
to set the guest pte dirty or accessed bits anyway, so this wasn't
really exploited.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16 12:05:44 +03:00
Avi Kivity
fd97dc516c KVM: MMU: Simpify accessed/dirty/present/nx bit handling
Always set the accessed and dirty bit (since having them cleared causes
a read-modify-write cycle), always set the present bit, and copy the
nx bit from the guest.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16 12:05:44 +03:00
Avi Kivity
e663ee64ae KVM: MMU: Make setting shadow ptes atomic on i386
Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16 12:05:44 +03:00
Avi Kivity
97a0a01ea9 KVM: MMU: Fold fix_write_pf() into set_pte_common()
This prevents some work from being performed twice, and, more importantly,
reduces the number of places where we modify shadow ptes.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16 12:05:43 +03:00
Avi Kivity
63b1ad24d2 KVM: MMU: Fold fix_read_pf() into set_pte_common()
Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16 12:05:43 +03:00
Avi Kivity
e60d75ea29 KVM: MMU: Move set_pte_common() to pte width dependent code
In preparation of some modifications.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16 12:05:43 +03:00
Avi Kivity
d3d25b048b KVM: MMU: Use slab caches for shadow pages and their headers
Use slab caches instead of a simple custom list.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16 12:05:43 +03:00
Avi Kivity
47ad8e689b KVM: MMU: Store shadow page tables as kernel virtual addresses, not physical
Simpifies things a bit.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16 12:05:40 +03:00
Avi Kivity
4b02d6daa1 KVM: MMU: Simplify kvm_mmu_free_page() a tiny bit
Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16 12:05:40 +03:00
Avi Kivity
0028425f64 KVM: Update shadow pte on write to guest pte
A typical demand page/copy on write pattern is:

- page fault on vaddr
- kvm propagates fault to guest
- guest handles fault, updates pte
- kvm traps write, clears shadow pte, resumes guest
- guest returns to userspace, re-faults on same vaddr
- kvm installs shadow pte, resumes guest
- guest continues

So, three vmexits for a single guest page fault.  But if instead of clearing
the page table entry, we update to correspond to the value that the guest
has just written, we eliminate the third vmexit.

This patch does exactly that, reducing kbuild time by about 10%.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16 12:05:39 +03:00
Avi Kivity
fce0657ff9 KVM: MMU: Respect nonpae pagetable quadrant when zapping ptes
When a guest writes to a page that has an mmu shadow, we have to clear
the shadow pte corresponding to the memory location touched by the guest.

Now, in nonpae mode, a single guest page may have two or four shadow
pages (because a nonpae page maps 4MB or 4GB, whereas the pae shadow maps
2MB or 1GB), so we when we look up the page we find up to three additional
aliases for the page.  Since we _clear_ the shadow pte, it doesn't matter
except for a slight performance penalty, but if we want to _update_ the
shadow pte instead of clearing it, it is vital that we don't modify the
aliases.

Fortunately, exactly which page is needed (the "quadrant") is easily
computed, and is accessible in the shadow page header.  All we need is
to ignore shadow pages from the wrong quadrants.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16 12:05:39 +03:00
Avi Kivity
09072daf37 KVM: Unify kvm_mmu_pre_write() and kvm_mmu_post_write()
Instead of calling two functions and repeating expensive checks, call one
function and provide it with before/after information.

Signed-off-by: Avi Kivity <avi@qumranet.com>
2007-07-16 12:05:38 +03:00