linux-kernel - Re: [RFC PATCH 16/33] Add support for Xen to entry.S.

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Message-ID: <20060718204333.GD2654@sequoia.sous-sol.org>
Date:	Tue, 18 Jul 2006 13:43:33 -0700
From:	Chris Wright <chrisw@...s-sol.org>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	Chris Wright <chrisw@...s-sol.org>, linux-kernel@...r.kernel.org,
	virtualization@...ts.osdl.org, xen-devel@...ts.xensource.com,
	Jeremy Fitzhardinge <jeremy@...p.org>, Andi Kleen <ak@...e.de>,
	Andrew Morton <akpm@...l.org>,
	Zachary Amsden <zach@...are.com>,
	Ian Pratt <ian.pratt@...source.com>,
	Christian Limpach <Christian.Limpach@...cam.ac.uk>,
	Jeremy Fitzhardinge <jeremy@...source.com>
Subject: Re: [RFC PATCH 16/33] Add support for Xen to entry.S.

* Rusty Russell (rusty@...tcorp.com.au) wrote:
> On Tue, 2006-07-18 at 00:00 -0700, Chris Wright wrote:
> > plain text document attachment (i386-entry.S)
> > - change cli/sti
> > - change test for user mode return to work for kernel mode in ring1
> > - check hypervisor saved event mask on return from exception
> > - add entry points for the hypervisor upcall handlers
> > - avoid math emulation check when running on Xen
> > - add nmi handler for running on Xen
> > 
> > Signed-off-by: Ian Pratt <ian.pratt@...source.com>
> > Signed-off-by: Christian Limpach <Christian.Limpach@...cam.ac.uk>
> > Signed-off-by: Jeremy Fitzhardinge <jeremy@...source.com>
> > Signed-off-by: Chris Wright <chrisw@...s-sol.org>
> > 
> > ---
> >  arch/i386/kernel/asm-offsets.c |   26 +++++++
> >  arch/i386/kernel/entry.S       |  141 ++++++++++++++++++++++++++++++++++++-----
> >  arch/i386/mach-xen/setup-xen.c |   19 +++++
> >  drivers/xen/core/features.c    |    2
> >  4 files changed, 169 insertions(+), 19 deletions(-)
> > 
> > diff -r 5cca1805b8a7 arch/i386/kernel/entry.S
> > --- a/arch/i386/kernel/entry.S	Tue Jul 18 02:20:39 2006 -0400
> > +++ b/arch/i386/kernel/entry.S	Tue Jul 18 02:22:56 2006 -0400
> > @@ -76,8 +76,39 @@ NT_MASK		= 0x00004000
> >  NT_MASK		= 0x00004000
> >  VM_MASK		= 0x00020000
> >  
> > +#ifndef CONFIG_XEN
> > +#define DISABLE_INTERRUPTS	cli
> > +#define ENABLE_INTERRUPTS	sti
> > +#else
> > +#include <xen/interface/xen.h>
> > +
> > +EVENT_MASK	= 0x2E
> > +
> > +/* Offsets into shared_info_t. */
> > +#define evtchn_upcall_pending		/* 0 */
> > +#define evtchn_upcall_mask		1
> 
> Erk... Can we get these into asm-offsets?

Hmm, we put the vcpu shift in, guess we missed that.  Thanks for noticing.

> > +
> > +#ifdef CONFIG_SMP
> > +/* Set %esi to point to the appropriate vcpu structure */
> > +#define GET_VCPU_INFO		movl TI_cpu(%ebp),%esi			; \
> > +				shl  $SIZEOF_VCPU_INFO_SHIFT,%esi	; \
> > +				addl HYPERVISOR_shared_info,%esi
> > +#else
> > +#define GET_VCPU_INFO		movl HYPERVISOR_shared_info,%esi
> > +#endif
> > +
> > +/* The following end up using/clobbering %esi, because of GET_VCPU_INFO */
> > +#define __DISABLE_INTERRUPTS	movb $1,evtchn_upcall_mask(%esi)
> > +#define DISABLE_INTERRUPTS	GET_VCPU_INFO				; \
> > +				__DISABLE_INTERRUPTS
> > +#define ENABLE_INTERRUPTS	GET_VCPU_INFO				; \
> > +				movb $0,evtchn_upcall_mask(%esi)
> > +#define __TEST_PENDING		testb $0xFF,evtchn_upcall_pending(%esi)
> > +#endif
> 
> Actually, is it possible to move these to a header somewhere?  In the
> paravirt_ops patches I used the names CLI and STI (copied from the VMI
> patches), but didn't allow them to clobber any regs.  They're defined in
> asm-i386/paravirt.h.

Sure, although it's only used here.  Got a preference?

> If we want to allow them to clobber %esi, then your names are probably
> better, but we should clobber %esi in the !CONFIG_XEN case too if
> CONFIG_DEBUG_KERNEL.

That makes sense to me, just to catch those bugs.

thanks,
-chris
-
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