Re: [Xen-devel] [PATCH 2/3] mini-os: cleanup x86_64.S

[Juergen Gross <jgross@xxxxxxxx>]

On 26/08/16 16:46, Andrew Cooper wrote:
> On 26/08/16 15:35, Juergen Gross wrote:
>> arch/x86/x86_64.S contains some unnecessary macros. Remove them.
>>
>> Add a SAVE_PARAVIRT macro for saving %rcx and %r11 on the stack in
>> case of CONFIG_PARAVIRT defined.
>>
>> Remove the parameter from HYPERVISOR_IRET macro as it is used with
>> 0 only.
>>
>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
>> ---
>>   arch/x86/x86_64.S | 44 ++++++++++++++++----------------------------
>>   1 file changed, 16 insertions(+), 28 deletions(-)
>>
>> diff --git a/arch/x86/x86_64.S b/arch/x86/x86_64.S
>> index 2046187..3a7116f 100644
>> --- a/arch/x86/x86_64.S
>> +++ b/arch/x86/x86_64.S
>> @@ -45,21 +45,10 @@ hypercall_page:
>>       #define XEN_GET_VCPU_INFO(reg)    movq HYPERVISOR_shared_info,reg
>> -#define XEN_PUT_VCPU_INFO(reg)
>> -#define XEN_PUT_VCPU_INFO_fixup
>>   #define XEN_LOCKED_BLOCK_EVENTS(reg)    movb $1,evtchn_upcall_mask(reg)
>>   #define XEN_LOCKED_UNBLOCK_EVENTS(reg)    movb
>> $0,evtchn_upcall_mask(reg)
>>   #define XEN_TEST_PENDING(reg)    testb $0xFF,evtchn_upcall_pending(reg)
>>   -#define XEN_BLOCK_EVENTS(reg)    XEN_GET_VCPU_INFO(reg)            ; \
>> -                                XEN_LOCKED_BLOCK_EVENTS(reg)    ; \
>> -                                XEN_PUT_VCPU_INFO(reg)
>> -
>> -#define XEN_UNBLOCK_EVENTS(reg)    XEN_GET_VCPU_INFO(reg)            ; \
>> -                                XEN_LOCKED_UNBLOCK_EVENTS(reg)    ; \
>> -                                XEN_PUT_VCPU_INFO(reg)
>> -
>> -
>>   /* Offsets into shared_info_t. */
>>   #define evtchn_upcall_pending        /* 0 */
>>   #define evtchn_upcall_mask        1
>> @@ -77,12 +66,16 @@ KERNEL_CS_MASK = 0xfc
>>       /* Macros */
>> +.macro SAVE_PARAVIRT
>> +#ifdef CONFIG_PARAVIRT
>> +    movq (%rsp),%rcx
>> +    movq 8(%rsp),%r11
>> +    addq $0x10,%rsp /* rsp points to the error code */iwt
> 
> I know this is just moving code, but I would recommend switching to a
> pop %rcx; pop %r11, which is shorter and more efficient.
> 
> It also plays better in the stack engine with the adjacent pushes/pops.

Right. I'll send a V2.


Juergen

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