LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Rusty Russell <rusty@rustcorp.com.au>
To: Andi Kleen <ak@muc.de>
Cc: virtualization@lists.osdl.org,
	lkml - Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@osdl.org>, Sam Ravnborg <sam@ravnborg.org>
Subject: Re: [PATCH 6/10] lguest code: the little linux hypervisor.
Date: Sat, 10 Feb 2007 02:01:57 +1100	[thread overview]
Message-ID: <1171033317.2718.161.camel@localhost.localdomain> (raw)
In-Reply-To: <20070209135739.GB18080@muc.de>

On Fri, 2007-02-09 at 14:57 +0100, Andi Kleen wrote:
> On Fri, Feb 09, 2007 at 11:39:31PM +1100, Rusty Russell wrote:
> > On Fri, 2007-02-09 at 11:09 +0100, Andi Kleen wrote:
> > > > +# This links the hypervisor in the right place and turns it into a C array.
> > > > +$(obj)/hypervisor-raw: $(obj)/hypervisor.o
> > > > +	@$(LD) -static -Tdata=`printf %#x $$(($(HYPE_ADDR)))` -Ttext=`printf %#x $$(($(HYPE_ADDR)+$(HYPE_DATA_SIZE)))` -o $@ $< && $(OBJCOPY) -O binary $@
> > > > +$(obj)/hypervisor-blob.c: $(obj)/hypervisor-raw
> > > > +	@od -tx1 -An -v $< | sed -e 's/^ /0x/' -e 's/$$/,/' -e 's/ /,0x/g' > $@
> > > 
> > > an .S file with .incbin is more efficient and simpler
> > > (note it has to be an separate .S file, otherwise icecream/distcc break) 
> > > 
> > > It won't allow to show off any sed skills, but I guess we can live with that ;-)
> > 
> > Good idea, except I currently use sizeof(hypervisor_blob): I'd have to
> > extract the size separately and hand it in the CFLAGS 8(
> 
> hypervisor_start:
> 	.incbin "hypervisor"
> hypervisor_end:
> 
> ...
> 	extern char hypervisor_start[], hypervisor_end[];
> 
> 	size = hypervisor_end - hypervisor_start;

#define MAX_LGUEST_GUESTS \
	((HYPERVISOR_SIZE-sizeof(hypervisor_blob))/sizeof(struct lguest_state))
struct lguest lguests[MAX_LGUEST_GUESTS];

I could kmalloc that array, of course, but is it worth it to get rid of
one line in a Makefile?

> > > Statics? looks funky.  Why only a single hypervisor_vma?
> > 
> > We only have one switcher: it contains an array of "struct
> > lguest_state"; one for each guest.  (This is host code we're looking at
> > here).
> 
> This means it is not SMP safe? 

No, it's host-SMP safe.  There's no guest SMP support though, which
keeps things nice and simple.

> > No, the guest should not be able to evoke a printk from the host kernel.
> 
> This means nobody will know why it failed.

No, that's why the lguest process gets the error string (and prints it
out).  Biggest usability improvement I made in a while.

The kernel log is the absolute worst place to report errors; iptables
and module code both do that and the #1 FAQ is "What happened?"

I didn't make the same mistake this (third) time!  Here's lguest when
the guest crashes:

        # lguest 64m bzImage ...
        ...
        lguest: CRASH: Attempted to kill init!
        # 

> > It would have to be a switch then gunk at the bottom, because those last
> > two tests don't switch-ify.  IIRC I changed back from a switch because
> > of that.
> 
> gcc has a handy extension for this: 
> 
> case 0...FIRST_EXTERNAL_VECTOR-1:
> case SYSCALL_VECTOR:
> case FIRST_EXTERNAL_VECTOR...FIRST_EXTERNAL_VECTOR+LGUEST_IRQS:

Indeed, and I really wanted to use it, but it still doesn't allow
overlapping ranges.  The first cases are in the middle of 0 ...
FIRST_EXTERNAL_VECTOR-1, and if LGUEST_IRQS is large enough, 
SYSCALL_VECTOR is in the middle of FIRST_EXTERNAL_VECTOR ...
FIRST_EXTERNAL_VECTOR+LGUEST_IRQS 8(

Nonetheless, I switchified what I could in my update (testing now).

> Re: the loops; e.g. we used to have possible loop cases
> when a page fault does read instructions and then causes another
> page fault etc.etc. I haven't seen any immediate danger of this,
> but it might be worth double checking.

OK, I'll run some tests here.  There shouldn't be any danger here
though....

Thanks!
Rusty.


  reply	other threads:[~2007-02-09 15:02 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-09  9:11 [PATCH 0/10] lguest Rusty Russell
2007-02-09  9:14 ` [PATCH 1/10] lguest: Don't rely on last-linked fallthru when no paravirt handler Rusty Russell
2007-02-09  9:15   ` [PATCH 2/10] lguest: Export symbols for lguest as a module Rusty Russell
2007-02-09  9:32     ` Andi Kleen
2007-02-09 12:06       ` Rusty Russell
2007-02-09 13:58         ` Andi Kleen
2007-02-10 11:39           ` Rusty Russell
2007-02-09  9:17   ` [PATCH 3/10] lguest: Expose get_futex_key, get_key_refs and drop_key_refs Rusty Russell
2007-02-09  9:18   ` [PATCH 4/10] lguest: Initialize esp0 properly all the time Rusty Russell
2007-02-09  9:19     ` [PATCH 5/10] Make hvc_console.c compile on non-PowerPC Rusty Russell
     [not found]       ` <1171012827.2718.42.camel@localhost.localdomain>
2007-02-09  9:22         ` [PATCH 7/10] lguest: Simple lguest network driver Rusty Russell
2007-02-09  9:23           ` [PATCH 8/10] lguest: console driver Rusty Russell
2007-02-09  9:24             ` [PATCH 9/10] lguest: block driver Rusty Russell
2007-02-09  9:25               ` [PATCH 10/10] lguest: documentatation including example launcher Rusty Russell
2007-02-09  9:35         ` [PATCH 6/10] lguest code: the little linux hypervisor Andrew Morton
2007-02-09 11:00           ` Rusty Russell
2007-02-09 11:13             ` Zachary Amsden
2007-02-09 11:50               ` Andi Kleen
2007-02-09 11:54                 ` Zachary Amsden
2007-02-09 11:57                   ` Andi Kleen
2007-02-09 12:08                     ` Zachary Amsden
2007-02-09 22:29                 ` David Miller
2007-02-09 10:09         ` Andi Kleen
2007-02-09 12:39           ` Rusty Russell
2007-02-09 13:57             ` Andi Kleen
2007-02-09 15:01               ` Rusty Russell [this message]
2007-02-09 14:17             ` Sam Ravnborg
2007-02-09 15:23               ` Rusty Russell
2007-02-12 13:34                 ` [q] kbuild for private asm-offsets (Re: [PATCH 6/10] lguest code: the little linux hypervisor.) Oleg Verych
2007-02-12 17:24                   ` Andi Kleen
2007-02-12 21:41                   ` Sam Ravnborg
2007-02-12 23:41                   ` Rusty Russell
2007-02-13  3:10                     ` Oleg Verych
2007-02-16 15:55                       ` [pp] kbuild: lguest with private asm-offsets (and some bloat) Oleg Verych
2007-02-16 15:59                         ` [pp] kbuild: asm-offsets generalized Oleg Verych
2007-02-16 18:56                           ` Sam Ravnborg
2007-02-16 21:56                             ` Oleg Verych
2007-02-17  4:43                               ` Rusty Russell
2007-02-17  5:33                                 ` Oleg Verych
2007-04-01 20:42                           ` Sam Ravnborg
2007-04-01 21:08                             ` Oleg Verych
2007-04-01 21:03                               ` Sam Ravnborg
2007-02-09 10:55       ` [PATCH 6a/10] lguest: Config and headers Rusty Russell
2007-02-09 10:56         ` [PATCH 6b/10] lguest: the host code (lg.ko) Rusty Russell
2007-02-09 10:57           ` [PATCH 6c/10] lguest: the guest code Rusty Russell
2007-02-09 10:58             ` [PATCH 6d/10] lguest: the Makefiles Rusty Russell
2007-02-09 17:06             ` [PATCH 6c/10] lguest: the guest code Len Brown
2007-02-09 17:14               ` James Morris
2007-02-09 17:49                 ` Len Brown
2007-02-09 23:48                   ` [PATCH 11/10] lguest: use disable_acpi() Rusty Russell
2007-02-09  9:31   ` [PATCH 1/10] lguest: Don't rely on last-linked fallthru when no paravirt handler Andi Kleen
2007-02-09 11:52     ` Rusty Russell
2007-02-09 20:49       ` Jeremy Fitzhardinge

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1171033317.2718.161.camel@localhost.localdomain \
    --to=rusty@rustcorp.com.au \
    --cc=ak@muc.de \
    --cc=akpm@osdl.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=sam@ravnborg.org \
    --cc=virtualization@lists.osdl.org \
    --subject='Re: [PATCH 6/10] lguest code: the little linux hypervisor.' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).