Every so often, after code shuffles, I need to go through and unbitrot
the Lguest Journey (see drivers/lguest/README). Since we now use RCU in
a simple form in one place I took the opportunity to expand that explanation.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
I don't really notice it (except to begrudge the extra vertical
space), but Ingo does. And he pointed out that one excuse of lguest
is as a teaching tool, it should set a good example.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@redhat.com>
We no longer need an efficient mechanism to force the Guest back into
host userspace, as each device is serviced without bothering the main
Guest process (aka. the Launcher).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Currently, when a Guest wants to perform I/O it calls LHCALL_NOTIFY with
an address: the main Launcher process returns with this address, and figures
out what device to run.
A far nicer model is to let processes bind an eventfd to an address: if we
find one, we simply signal the eventfd.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Davide Libenzi <davidel@xmailserver.org>
lguest never checked for pending interrupts when enabling interrupts, and
things still worked. However, it makes a significant difference to TCP
performance, so it's time we fixed it by introducing a pending_irq flag
and checking it on irq_restore and irq_enable.
These two routines are now too big to patch into the 8/10 bytes
patch space, so we drop that code.
Note: The high latency on interrupt delivery had a very curious
effect: once everything else was optimized, networking without GSO was
faster than networking with GSO, since more interrupts were sent and
hence a greater chance of one getting through to the Guest!
Note2: (Almost) Closing the same loophole for iret doesn't have any
measurable effect, so I'm leaving that patch for the moment.
Before:
1GB tcpblast Guest->Host: 30.7 seconds
1GB tcpblast Guest->Host (no GSO): 76.0 seconds
After:
1GB tcpblast Guest->Host: 6.8 seconds
1GB tcpblast Guest->Host (no GSO): 27.8 seconds
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
When the Guest does the LHCALL_HALT hypercall, we go to sleep, expecting
that a timer or the Waker will wake_up_process() us.
But we do it in a stupid way, leaving a classic missing wakeup race.
So split maybe_do_interrupt() into interrupt_pending() and
try_deliver_interrupt(), and check maybe_do_interrupt() and the
"break_out" flag before calling schedule.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Impact: clean up
Rusty told me, some time ago, that he had become a fan of "bool".
So, here are some replacements.
Signed-off-by: Matias Zabaljauregui <zabaljauregui at gmail.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
map_switcher allocates the array, unmap_switcher has to free it
accordingly.
Signed-off-by: Johannes Weiner <hannes@saeurebad.de>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Took some cycles to re-read the Lguest Journey end-to-end, fix some
rot and tighten some phrases.
Only comments change. No new jokes, but a couple of recycled old jokes.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Robert Bragg's 5dc3318528 tightened
(ie. fixed) the checking in __get_vm_area, and it broke lguest.
lguest should pass the exact "end" it wants, not some random constant
(it was possible previously that it would actually get an address
different from SWITCHER_ADDR).
Also, Fabio Checconi pointed out that we should make sure we're not
hitting the fixmap area.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Robert Bragg <robert@sixbynine.org>
We can save some lines of code by getting rid of
*lg = cpu... lines of code spread everywhere by now.
Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
this patch makes the pending_notify field, used to control
pending notifications, per-vcpu, instead of per-guest
Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
lguest uses tasks to control its running behaviour (like sending
breaks, controlling halted state, etc). In a per-vcpu environment,
each vcpu will have its own underlying task. So this patch
makes the infrastructure for that possible
Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This patch adapts interrupt processing for using the vcpu struct.
Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
this patch changes do_hcall() and do_async_hcall() interfaces (and obviously their
callers) to get a vcpu struct. Again, a vcpu services the hypercall, not the whole
guest
Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This patch makes the run_guest() routine use the lg_cpu struct.
This is required since in a smp guest environment, there's no
more the notion of "running the guest", but rather, it is "running the vcpu"
Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Currently, lguest module can't be compiled without the PARAVIRT flag being
on. This is a fake dependency, since the module itself shouldn't need any
paravirt override. Reason for that is the reference to pv_info structure
in initial loading tests.
This patch removes it in favour of a more generic error message.
Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Went through the documentation doing typo and content fixes. This
patch contains only comment and whitespace changes.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Jes complains that page table code still uses lgread_u32 even though
it now uses general kernel pte types. The best thing to do is to
generalize lgread_u32 and lgwrite_u32.
This means we lose the efficiency of getuser(). We could potentially
regain it if we used __copy_from_user instead of copy_from_user, but
I'm not certain that our range check is equivalent to access_ok() on
all platforms.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Jes Sorensen <jes@sgi.com>
This patch gets rid of the old lguest host I/O infrastructure and
replaces it with a single hypercall "LHCALL_NOTIFY" which takes an
address.
The main change is the removal of io.c: that mainly did inter-guest
I/O, which virtio doesn't yet support.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
(Based on Ron Minnich's LGUEST_PLAN9_SYSCALL patch).
This patch allows Guests to specify what system call vector they want,
and we try to reserve it. We only allow one non-Linux system call
vector, to try to avoid DoS on the Host.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Currently we look at the "trapnum" to see if the Guest wants a
hypercall. But once the hypercall is done we have to reset trapnum to
a bogus value, otherwise if we exit to userspace and return, we'd run
the same hypercall twice (that was a nasty bug to find!).
This has two main effects:
1) When Jes's patch changes the hypercall args to be a generic "struct
hcall_args" we simply change the type of "lg->hcall". It's set by
arch code, so if it has to copy args or something it can do so, and
point "hcall" into lg->arch somewhere.
2) Async hypercalls only get run when an actual hypercall is pending.
This simplfies the code a little and is a more logical semantic.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Separate i386 architecture specific from core.c and move it to
x86/core.c and add x86/lguest.h header file to match.
Signed-off-by: Jes Sorensen <jes@sgi.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Back when we had all the Guest state in the switcher, we had a fixed
array of them. This is no longer necessary.
If we switch the network code to using random_ether_addr (46 bits is
enough to avoid clashes), we can get rid of the concept of "guest id"
altogether.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
In order to avoid problematic special linking of the Launcher, we give
the Host an offset: this means we can use any memory region in the
Launcher as Guest memory rather than insisting on mmap() at 0.
The result is quite pleasing: a number of casts are replaced with
simple additions.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This patch refactors the paravirt_ops structure into groups of
functionally related ops:
pv_info - random info, rather than function entrypoints
pv_init_ops - functions used at boot time (some for module_init too)
pv_misc_ops - lazy mode, which didn't fit well anywhere else
pv_time_ops - time-related functions
pv_cpu_ops - various privileged instruction ops
pv_irq_ops - operations for managing interrupt state
pv_apic_ops - APIC operations
pv_mmu_ops - operations for managing pagetables
There are several motivations for this:
1. Some of these ops will be general to all x86, and some will be
i386/x86-64 specific. This makes it easier to share common stuff
while allowing separate implementations where needed.
2. At the moment we must export all of paravirt_ops, but modules only
need selected parts of it. This allows us to export on a case by case
basis (and also choose which export license we want to apply).
3. Functional groupings make things a bit more readable.
Struct paravirt_ops is now only used as a template to generate
patch-site identifiers, and to extract function pointers for inserting
into jmp/calls when patching. It is only instantiated when needed.
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andi Kleen <ak@suse.de>
Cc: Zach Amsden <zach@vmware.com>
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>
If a Guest makes hypercall which sets a GDT entry to not present, we
currently set any segment registers using that GDT entry to 0.
Unfortunately, this is not sufficient: there are other ways of
altering GDT entries which will cause a fault.
The correct solution to do what Linux does: let them set any GDT value
they want and handle the #GP when popping causes a fault. This has
the added benefit of making our Switcher slightly more robust in the
case of any other bugs which cause it to fault.
We kill the Guest if it causes a fault in the Switcher: it's the
Guest's responsibility to make sure it's not using segments when it
changes them.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Documentation: The Switcher
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Documentation: The Host
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Documentation: The Launcher
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The netfilter code had very good documentation: the Netfilter Hacking HOWTO.
Noone ever read it.
So this time I'm trying something different, using a bit of Knuthiness.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is the code for the "lg.ko" module, which allows lguest guests to
be launched.
[akpm@linux-foundation.org: update for futex-new-private-futexes]
[akpm@linux-foundation.org: build fix]
[jmorris@namei.org: lguest: use hrtimers]
[akpm@linux-foundation.org: x86_64 build fix]
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andi Kleen <ak@suse.de>
Cc: Eric Dumazet <dada1@cosmosbay.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
