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Date:   Wed, 9 Mar 2022 07:18:40 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc:     Christoph Hellwig <hch@lst.de>, iommu@lists.linux-foundation.org,
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Subject: Re: [PATCH 11/12] swiotlb: merge swiotlb-xen initialization into
 swiotlb
Message-ID: <20220309061840.GA31435@lst.de>
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On Tue, Mar 08, 2022 at 04:38:21PM -0500, Boris Ostrovsky wrote:
>
> On 3/1/22 5:53 AM, Christoph Hellwig wrote:
>> Allow to pass a remap argument to the swiotlb initialization functions
>> to handle the Xen/x86 remap case.  ARM/ARM64 never did any remapping
>> from xen_swiotlb_fixup, so we don't even need that quirk.
>
>
> Any chance this patch could be split? Lots of things are happening here and it's somewhat hard to review. (Patch 7 too BTW but I think I managed to get through it)

What would be your preferred split?

>> diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
>> index e0def4b1c3181..2f2c468acb955 100644
>> --- a/arch/x86/kernel/pci-dma.c
>> +++ b/arch/x86/kernel/pci-dma.c
>> @@ -71,15 +71,12 @@ static inline void __init pci_swiotlb_detect(void)
>>   #endif /* CONFIG_SWIOTLB */
>>     #ifdef CONFIG_SWIOTLB_XEN
>> -static bool xen_swiotlb;
>> -
>>   static void __init pci_xen_swiotlb_init(void)
>>   {
>>   	if (!xen_initial_domain() && !x86_swiotlb_enable)
>>   		return;
>
>
> Now that there is a single call site for this routine I think this check can be dropped. We are only called here for xen_initial_domain()==true.

The callsite just checks xen_pv_domain() and itself is called
unconditionally during initialization.