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  1. 25 6月, 2008 2 次提交
    • J
      xen: add mechanism to extend existing multicalls · 400d3494
      由 Jeremy Fitzhardinge 提交于 
      Some Xen hypercalls accept an array of operations to work on.  In
general this is because its more efficient for the hypercall to the
work all at once rather than as separate hypercalls (even batched as a
multicall).

This patch adds a mechanism (xen_mc_extend_args()) to allocate more
argument space to the last-issued multicall, in order to extend its
argument list.

The user of this mechanism is xen/mmu.c, which uses it to extend the
args array of mmu_update.  This is particularly valuable when doing
the update for a large mprotect, which goes via
ptep_modify_prot_commit(), but it also manages to batch updates to
pgd/pmds as well.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Acked-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      400d3494
    • J
      xen: implement ptep_modify_prot_start/commit · e57778a1
      由 Jeremy Fitzhardinge 提交于 
      Xen has a pte update function which will update a pte while preserving
its accessed and dirty bits.  This means that ptep_modify_prot_start() can be
implemented as a simple read of the pte value.  The hardware may
update the pte in the meantime, but ptep_modify_prot_commit() updates it while
preserving any changes that may have happened in the meantime.

The updates in ptep_modify_prot_commit() are batched if we're currently in lazy
mmu mode.

The mmu_update hypercall can take a batch of updates to perform, but
this code doesn't make particular use of that feature, in favour of
using generic multicall batching to get them all into the hypervisor.

The net effect of this is that each mprotect pte update turns from two
expensive trap-and-emulate faults into they hypervisor into a single
hypercall whose cost is amortized in a batched multicall.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Acked-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      e57778a1
  3. 24 6月, 2008 1 次提交
  5. 20 6月, 2008 4 次提交
  7. 02 6月, 2008 2 次提交
  9. 28 5月, 2008 1 次提交
    • I
      xen: fix early bootup crash on native hardware · b20aeccd
      由 Ingo Molnar 提交于 
      -tip tree auto-testing found the following early bootup hang:

-------------->
get_memcfg_from_srat: assigning address to rsdp
RSD PTR  v0 [Nvidia]
BUG: Int 14: CR2 ffd00040
     EDI 8092fbfe  ESI ffd00040  EBP 80b0aee8  ESP 80b0aed0
     EBX 000f76f0  EDX 0000000e  ECX 00000003  EAX ffd00040
     err 00000000  EIP 802c055a   CS 00000060  flg 00010006
Stack: ffd00040 80bc78d0 80b0af6c 80b1dbfe 8093d8ba 00000008 80b42810 80b4ddb4
       80b42842 00000000 80b0af1c 801079c8 808e724e 00000000 80b42871 802c0531
       00000100 00000000 0003fff0 80b0af40 80129999 00040100 00040100 00000000
Pid: 0, comm: swapper Not tainted 2.6.26-rc4-sched-devel.git #570
 [<802c055a>] ? strncmp+0x11/0x25
 [<80b1dbfe>] ? get_memcfg_from_srat+0xb4/0x568
 [<801079c8>] ? mcount_call+0x5/0x9
 [<802c0531>] ? strcmp+0xa/0x22
 [<80129999>] ? printk+0x38/0x3a
 [<80129999>] ? printk+0x38/0x3a
 [<8011b122>] ? memory_present+0x66/0x6f
 [<80b216b4>] ? setup_memory+0x13/0x40c
 [<80b16b47>] ? propagate_e820_map+0x80/0x97
 [<80b1622a>] ? setup_arch+0x248/0x477
 [<80129999>] ? printk+0x38/0x3a
 [<80b11759>] ? start_kernel+0x6e/0x2eb
 [<80b110fc>] ? i386_start_kernel+0xeb/0xf2
 =======================
<------

with this config:

   http://redhat.com/~mingo/misc/config-Wed_May_28_01_33_33_CEST_2008.bad

The thing is, the crash makes little sense at first sight. We crash on a
benign-looking printk. The code around it got changed in -tip but
checking those topic branches individually did not reproduce the bug.

Bisection led to this commit:

|   d5edbc1f is first bad commit
|   commit d5edbc1f
|   Author: Jeremy Fitzhardinge <jeremy@goop.org>
|   Date:   Mon May 26 23:31:22 2008 +0100
|
|   xen: add p2m mfn_list_list

Which is somewhat surprising, as on native hardware Xen client side
should have little to no side-effects.

After some head scratching, it turns out the following happened:
randconfig enabled the following Xen options:

  CONFIG_XEN=y
  CONFIG_XEN_MAX_DOMAIN_MEMORY=8
  # CONFIG_XEN_BLKDEV_FRONTEND is not set
  # CONFIG_XEN_NETDEV_FRONTEND is not set
  CONFIG_HVC_XEN=y
  # CONFIG_XEN_BALLOON is not set

which activated this piece of code in arch/x86/xen/mmu.c:

> @@ -69,6 +69,13 @@
>  	__attribute__((section(".data.page_aligned"))) =
>  		{ [ 0 ... TOP_ENTRIES - 1] = &p2m_missing[0] };
>
> +/* Arrays of p2m arrays expressed in mfns used for save/restore */
> +static unsigned long p2m_top_mfn[TOP_ENTRIES]
> +	__attribute__((section(".bss.page_aligned")));
> +
> +static unsigned long p2m_top_mfn_list[TOP_ENTRIES / P2M_ENTRIES_PER_PAGE]
> +	__attribute__((section(".bss.page_aligned")));

The problem is, you must only put variables into .bss.page_aligned that
have a _size_ that is _exactly_ page aligned. In this case the size of
p2m_top_mfn_list is not page aligned:

 80b8d000 b p2m_top_mfn
 80b8f000 b p2m_top_mfn_list
 80b8f008 b softirq_stack
 80b97008 b hardirq_stack
 80b9f008 b bm_pte

So all subsequent variables get unaligned which, depending on luck,
breaks the kernel in various funny ways. In this case what killed the
kernel first was the misaligned bootmap pte page, resulting in that
creative crash above.

Anyway, this was a fun bug to track down :-)

I think the moral is that .bss.page_aligned is a dangerous construct in
its current form, and the symptoms of breakage are very non-trivial, so
i think we need build-time checks to make sure all symbols in
.bss.page_aligned are truly page aligned.

The Xen fix below gets the kernel booting again.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      b20aeccd
  11. 27 5月, 2008 5 次提交
  13. 23 5月, 2008 2 次提交
  15. 28 4月, 2008 1 次提交
  17. 25 4月, 2008 4 次提交
  19. 05 4月, 2008 1 次提交
  21. 10 2月, 2008 1 次提交
  23. 30 1月, 2008 4 次提交
  25. 30 11月, 2007 1 次提交
  27. 18 10月, 2007 1 次提交
  29. 17 10月, 2007 4 次提交
    • J
      xen: lock pte pages while pinning/unpinning · 74260714
      由 Jeremy Fitzhardinge 提交于 
      When a pagetable is created, it is made globally visible in the rmap
prio tree before it is pinned via arch_dup_mmap(), and remains in the
rmap tree while it is unpinned with arch_exit_mmap().

This means that other CPUs may race with the pinning/unpinning
process, and see a pte between when it gets marked RO and actually
pinned, causing any pte updates to fail with write-protect faults.

As a result, all pte pages must be properly locked, and only unlocked
once the pinning/unpinning process has finished.

In order to avoid taking spinlocks for the whole pagetable - which may
overflow the PREEMPT_BITS portion of preempt counter - it locks and pins
each pte page individually, and then finally pins the whole pagetable.
Signed-off-by: NJeremy Fitzhardinge <jeremy@xensource.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Hugh Dickens <hugh@veritas.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andi Kleen <ak@suse.de>
Cc: Keir Fraser <keir@xensource.com>
Cc: Jan Beulich <jbeulich@novell.com>
      74260714
    • J
      xen: deal with stale cr3 values when unpinning pagetables · 9f79991d
      由 Jeremy Fitzhardinge 提交于 
      When a pagetable is no longer in use, it must be unpinned so that its
pages can be freed.  However, this is only possible if there are no
stray uses of the pagetable.  The code currently deals with all the
usual cases, but there's a rare case where a vcpu is changing cr3, but
is doing so lazily, and the change hasn't actually happened by the time
the pagetable is unpinned, even though it appears to have been completed.

This change adds a second per-cpu cr3 variable - xen_current_cr3 -
which tracks the actual state of the vcpu cr3.  It is only updated once
the actual hypercall to set cr3 has been completed.  Other processors
wishing to unpin a pagetable can check other vcpu's xen_current_cr3
values to see if any cross-cpu IPIs are needed to clean things up.

[ Stable folks: 2.6.23 bugfix ]
Signed-off-by: NJeremy Fitzhardinge <jeremy@xensource.com>
Cc: Stable Kernel <stable@kernel.org>
      9f79991d
    • J
      Clean up duplicate includes in arch/i386/xen/ · d626a1f1
      由 Jesper Juhl 提交于 
      This patch cleans up duplicate includes in
	arch/i386/xen/
Signed-off-by: NJesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: NJeremy Fitzhardinge <jeremy@xensource.com>
      d626a1f1
    • J
      paravirt: clean up lazy mode handling · 8965c1c0
      由 Jeremy Fitzhardinge 提交于 
      Currently, the set_lazy_mode pv_op is overloaded with 5 functions:
 1. enter lazy cpu mode
 2. leave lazy cpu mode
 3. enter lazy mmu mode
 4. leave lazy mmu mode
 5. flush pending batched operations

This complicates each paravirt backend, since it needs to deal with
all the possible state transitions, handling flushing, etc. In
particular, flushing is quite distinct from the other 4 functions, and
seems to just cause complication.

This patch removes the set_lazy_mode operation, and adds "enter" and
"leave" lazy mode operations on mmu_ops and cpu_ops.  All the logic
associated with enter and leaving lazy states is now in common code
(basically BUG_ONs to make sure that no mode is current when entering
a lazy mode, and make sure that the mode is current when leaving).
Also, flush is handled in a common way, by simply leaving and
re-entering the lazy mode.

The result is that the Xen, lguest and VMI lazy mode implementations
are much simpler.
Signed-off-by: NJeremy Fitzhardinge <jeremy@xensource.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Zach Amsden <zach@vmware.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Avi Kivity <avi@qumranet.com>
Cc: Anthony Liguory <aliguori@us.ibm.com>
Cc: "Glauber de Oliveira Costa" <glommer@gmail.com>
Cc: Jun Nakajima <jun.nakajima@intel.com>
      8965c1c0
  31. 11 10月, 2007 1 次提交
  33. 27 9月, 2007 1 次提交
  35. 18 7月, 2007 4 次提交
    • J
      xen: lazy-mmu operations · d66bf8fc
      由 Jeremy Fitzhardinge 提交于 
      This patch uses the lazy-mmu hooks to batch mmu operations where
possible.  This is primarily useful for batching operations applied to
active pagetables, which happens during mprotect, munmap, mremap and
the like (mmap does not do bulk pagetable operations, so it isn't
helped).
Signed-off-by: NJeremy Fitzhardinge <jeremy@xensource.com>
Acked-by: NChris Wright <chrisw@sous-sol.org>
      d66bf8fc
    • J
      xen: Add support for preemption · f120f13e
      由 Jeremy Fitzhardinge 提交于 
      Add Xen support for preemption.  This is mostly a cleanup of existing
preempt_enable/disable calls, or just comments to explain the current
usage.
Signed-off-by: NJeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: NChris Wright <chrisw@sous-sol.org>
      f120f13e
    • J
      xen: SMP guest support · f87e4cac
      由 Jeremy Fitzhardinge 提交于 
      This is a fairly straightforward Xen implementation of smp_ops.

Xen has its own IPI mechanisms, and has no dependency on any
APIC-based IPI.  The smp_ops hooks and the flush_tlb_others pv_op
allow a Xen guest to avoid all APIC code in arch/i386 (the only apic
operation is a single apic_read for the apic version number).

One subtle point which needs to be addressed is unpinning pagetables
when another cpu may have a lazy tlb reference to the pagetable. Xen
will not allow an in-use pagetable to be unpinned, so we must find any
other cpus with a reference to the pagetable and get them to shoot
down their references.
Signed-off-by: NJeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: NChris Wright <chrisw@sous-sol.org>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Andi Kleen <ak@suse.de>
      f87e4cac
    • J
      xen: Complete pagetable pinning · f4f97b3e
      由 Jeremy Fitzhardinge 提交于 
      Xen requires all active pagetables to be marked read-only.  When the
base of the pagetable is loaded into %cr3, the hypervisor validates
the entire pagetable and only allows the load to proceed if it all
checks out.

This is pretty slow, so to mitigate this cost Xen has a notion of
pinned pagetables.  Pinned pagetables are pagetables which are
considered to be active even if no processor's cr3 is pointing to is.
This means that it must remain read-only and all updates are validated
by the hypervisor.  This makes context switches much cheaper, because
the hypervisor doesn't need to revalidate the pagetable each time.

This also adds a new paravirt hook which is called during setup once
the zones and memory allocator have been initialized.  When the
init_mm pagetable is first built, the struct page array does not yet
exist, and so there's nowhere to put he init_mm pagetable's PG_pinned
flags.  Once the zones are initialized and the struct page array
exists, we can set the PG_pinned flags for those pages.

This patch also adds the Xen support for pte pages allocated out of
highmem (highpte) by implementing xen_kmap_atomic_pte.
Signed-off-by: NJeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: NChris Wright <chrisw@sous-sol.org>
Cc: Zach Amsden <zach@vmware.com>
      f4f97b3e