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

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

Chris Wright wrote:
> * Rusty Russell (rusty@xxxxxxxxxxxxxxx) 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@xxxxxxxxxxxxx>
> > > Signed-off-by: Christian Limpach <Christian.Limpach@xxxxxxxxxxxx>
> > > Signed-off-by: Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>
> > > Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>
> > >
> > > ---
> > >  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?
>   
It might be an idea to use something other than STI, CLI and CPUID, 
since the assembler is case-insensitive.  We've already had one bug 
where CPUID didn't get replaced and the assembler quietly accepted it as-is.
   J

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