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

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Date:	Tue, 18 Jul 2006 16:03:13 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Chris Wright <chrisw@...s-sol.org>
CC:	Rusty Russell <rusty@...tcorp.com.au>,
	linux-kernel@...r.kernel.org, virtualization@...ts.osdl.org,
	xen-devel@...ts.xensource.com, 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.

Chris Wright wrote:
> * 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?
>   

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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