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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>
Subject: Re: [PATCH 2/10] lguest: Export symbols for lguest as a module
Date: Sat, 10 Feb 2007 22:39:32 +1100	[thread overview]
Message-ID: <1171107572.15356.29.camel@localhost.localdomain> (raw)
In-Reply-To: <20070209135855.GC18080@muc.de>

On Fri, 2007-02-09 at 14:58 +0100, Andi Kleen wrote:
> On Fri, Feb 09, 2007 at 11:06:06PM +1100, Rusty Russell wrote:
> > On Fri, 2007-02-09 at 10:32 +0100, Andi Kleen wrote:
> > > Are you sure this will work with varying TSC frequencies? 
> > 
> > I'm actually quite sure it doesn't (there's a FIXME in the lguest code).
> > Given the debate over how useful the TSC was, I originally didn't use
> > it, but (1) it's simple, and (2) when it doesn't change, it's pretty
> > accurate.
> 
> But when it changes users become pretty unhappy

True.  Simplest fix is below.  There are several time issues on the TODO
list, and I will simply add this one.

Thanks!
Rusty.

lguest: Don't use the TSC in guest.

Andi complained that lguest guests don't deal with host TSC speed
changing.  Close this can of worms by not using the TSC in the guest.
Later on we could do something clever when we overhaul this to deal
with stolen time (also on the TODO list).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

===================================================================
--- a/arch/i386/kernel/tsc.c
+++ b/arch/i386/kernel/tsc.c
@@ -475,4 +475,3 @@ static int __init init_tsc_clocksource(v
 }
 
 module_init(init_tsc_clocksource);
-EXPORT_SYMBOL_GPL(tsc_khz);
===================================================================
--- a/arch/i386/lguest/hypercalls.c
+++ b/arch/i386/lguest/hypercalls.c
@@ -18,7 +18,6 @@
 #include <linux/uaccess.h>
 #include <linux/syscalls.h>
 #include <linux/mm.h>
-#include <linux/clocksource.h>
 #include <asm/lguest.h>
 #include <asm/page.h>
 #include <asm/pgtable.h>
@@ -179,8 +178,6 @@ int hypercall(struct lguest *lg, struct 
 		/* We reserve the top pgd entry. */
 		put_user(4U*1024*1024, &lg->lguest_data->reserve_mem);
 		put_user(lg->guestid, &lg->lguest_data->guestid);
-		put_user(clocksource_khz2mult(tsc_khz, 22),
-			 &lg->lguest_data->clock_mult);
 		return 0;
 	}
 	pending = do_hcall(lg, regs);
===================================================================
--- a/arch/i386/lguest/lguest.c
+++ b/arch/i386/lguest/lguest.c
@@ -25,7 +25,6 @@
 #include <linux/screen_info.h>
 #include <linux/irq.h>
 #include <linux/interrupt.h>
-#include <linux/clocksource.h>
 #include <asm/paravirt.h>
 #include <asm/lguest.h>
 #include <asm/lguest_user.h>
@@ -138,29 +137,10 @@ static struct notifier_block paniced = {
 	.notifier_call = lguest_panic
 };
 
-static cycle_t lguest_clock_read(void)
-{
-	/* FIXME: This is just the native one.  Account stolen time! */
-	return paravirt_ops.read_tsc();
-}
-
-/* FIXME: Update iff tsc rate changes. */
-static struct clocksource lguest_clock = {
-	.name			= "lguest",
-	.rating			= 400,
-	.read			= lguest_clock_read,
-	.mask			= CLOCKSOURCE_MASK(64),
-	.mult			= 0, /* to be set */
-	.shift			= 22,
-	.is_continuous		= 1,
-};
-
 static char *lguest_memory_setup(void)
 {
 	/* We do these here because lockcheck barfs if before start_kernel */
 	atomic_notifier_chain_register(&panic_notifier_list, &paniced);
-	lguest_clock.mult = lguest_data.clock_mult;
-	clocksource_register(&lguest_clock);
 
 	e820.nr_map = 0;
 	add_memory_region(0, PFN_PHYS(boot->max_pfn), E820_RAM);
===================================================================
--- a/include/asm-i386/lguest.h
+++ b/include/asm-i386/lguest.h
@@ -74,8 +74,6 @@ struct lguest_data
 	unsigned long reserve_mem;
 	/* ID of this guest (used by network driver to set ethernet address) */
 	u16 guestid;
-	/* Multiplier for TSC clock. */
-	u32 clock_mult;
 
 /* Fields initialized by the guest at boot: */
 	/* Instruction range to suppress interrupts even if enabled */



  reply	other threads:[~2007-02-10 11:40 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 [this message]
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
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

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