Re: [Xen-devel] [PATCH 3/3] xen/MSI: Retrieve MSI msg from cached msi_desc->msg

[Yijing Wang <wangyijing@xxxxxxxxxx>]

On 2014/8/15 11:51, Konrad Rzeszutek Wilk wrote:
> On Fri, Aug 15, 2014 at 11:14:37AM +0800, Yijing Wang wrote:
>> We had cached the MSI msg in __write_msi_msg(),
>> so we should retrieve the cached MSI msg directly,
>> not to access the MSI address/data hardware registers
>> again.
> 
> Is this fixing a particular problem?
> 
> Could you kindly explain to me when you do the __write_msi_msg
> before doing an read_msi_msg? The order of operation in this
> function is read, and then write.

Hi Konrad,
   Thanks for your review and comments. It looks like I made a mistake.
Before I thought xen_hvm_setup_msi_irqs() here worked like restore MSI irq,
but it seems not in real. Since every time we call the setup MSI irq function,
the msi_desc always new allocated, so here should use read_msi_msg(),
I'm sorry for my mistake. :(

Bjorn, please drop this one.

Thanks!
Yijing.

> 
>>
>> Signed-off-by: Yijing Wang <wangyijing@xxxxxxxxxx>
>> CC: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
>> CC: xen-devel@xxxxxxxxxxxxxxxxxxxx
>> ---
>>  arch/x86/pci/xen.c |    2 +-
>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
>> index 4656099..7a74404 100644
>> --- a/arch/x86/pci/xen.c
>> +++ b/arch/x86/pci/xen.c
>> @@ -228,7 +228,7 @@ static int xen_hvm_setup_msi_irqs(struct pci_dev *dev, 
>> int nvec, int type)
>>              return 1;
>>  
>>      list_for_each_entry(msidesc, &dev->msi_list, list) {
>> -            read_msi_msg(msidesc, &msg);
>> +            get_cached_msi_msg(msidesc, &msg);
>>              pirq = MSI_ADDR_EXT_DEST_ID(msg.address_hi) |
>>                      ((msg.address_lo >> MSI_ADDR_DEST_ID_SHIFT) & 0xff);
>>              if (msg.data != XEN_PIRQ_MSI_DATA ||
>> -- 
>> 1.7.1
>>
> 
> 


-- 
Thanks!
Yijing


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