linux-kernel - Re: [PATCH v7 9/9] iommu/vt-d: Add iotlb flush for nested domain

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Date: Tue, 26 Dec 2023 12:51:39 +0800
From: Yi Liu <yi.l.liu@...el.com>
To: "Tian, Kevin" <kevin.tian@...el.com>, "joro@...tes.org" <joro@...tes.org>,
	"alex.williamson@...hat.com" <alex.williamson@...hat.com>, "jgg@...dia.com"
	<jgg@...dia.com>, "robin.murphy@....com" <robin.murphy@....com>,
	"baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>
CC: "cohuck@...hat.com" <cohuck@...hat.com>, "eric.auger@...hat.com"
	<eric.auger@...hat.com>, "nicolinc@...dia.com" <nicolinc@...dia.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, "mjrosato@...ux.ibm.com"
	<mjrosato@...ux.ibm.com>, "chao.p.peng@...ux.intel.com"
	<chao.p.peng@...ux.intel.com>, "yi.y.sun@...ux.intel.com"
	<yi.y.sun@...ux.intel.com>, "peterx@...hat.com" <peterx@...hat.com>,
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	<shameerali.kolothum.thodi@...wei.com>, "lulu@...hat.com" <lulu@...hat.com>,
	"suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
	"iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>, "Duan,
 Zhenzhong" <zhenzhong.duan@...el.com>, "joao.m.martins@...cle.com"
	<joao.m.martins@...cle.com>, "Zeng, Xin" <xin.zeng@...el.com>, "Zhao, Yan Y"
	<yan.y.zhao@...el.com>, "j.granados@...sung.com" <j.granados@...sung.com>
Subject: Re: [PATCH v7 9/9] iommu/vt-d: Add iotlb flush for nested domain

On 2023/12/22 14:57, Tian, Kevin wrote:
>> From: Liu, Yi L <yi.l.liu@...el.com>
>> Sent: Thursday, December 21, 2023 11:40 PM
>>
>> +
>> +static void intel_nested_flush_cache(struct dmar_domain *domain, u64
>> addr,
>> +				     unsigned long npages, u32 *error)
>> +{
>> +	struct iommu_domain_info *info;
>> +	unsigned long i;
>> +	unsigned mask;
>> +	u32 fault = 0;
>> +
>> +	if (npages == U64_MAX)
>> +		mask = 64 - VTD_PAGE_SHIFT;
>> +	else
>> +		mask = ilog2(__roundup_pow_of_two(npages));
>> +
>> +	xa_for_each(&domain->iommu_array, i, info) {
>> +		nested_flush_pasid_iotlb(info->iommu, domain, addr,
>> npages, 0);
> 
> so IOMMU_VTD_INV_FLAGS_LEAF is defined but ignored?

yeah... it is. It is named as ih in the driver code. But it appears only
the below code is set ih. When calling iommu_flush_iotlb_psi(), the 5th
parameter (ih) may be true.

static int intel_iommu_memory_notifier(struct notifier_block *nb,
				       unsigned long val, void *v)
{
	struct memory_notify *mhp = v;
	unsigned long start_vpfn = mm_to_dma_pfn(mhp->start_pfn);
	unsigned long last_vpfn = mm_to_dma_pfn(mhp->start_pfn +
			mhp->nr_pages - 1);

	switch (val) {
	case MEM_GOING_ONLINE:
		if (iommu_domain_identity_map(si_domain,
					      start_vpfn, last_vpfn)) {
			pr_warn("Failed to build identity map for [%lx-%lx]\n",
				start_vpfn, last_vpfn);
			return NOTIFY_BAD;
		}
		break;

	case MEM_OFFLINE:
	case MEM_CANCEL_ONLINE:
		{
			struct dmar_drhd_unit *drhd;
			struct intel_iommu *iommu;
			LIST_HEAD(freelist);

			domain_unmap(si_domain, start_vpfn, last_vpfn, &freelist);

			rcu_read_lock();
			for_each_active_iommu(iommu, drhd)
				iommu_flush_iotlb_psi(iommu, si_domain,
					start_vpfn, mhp->nr_pages,
					list_empty(&freelist), 0);
			rcu_read_unlock();
			put_pages_list(&freelist);
		}
		break;
	}

	return NOTIFY_OK;
}

> 
>> +
>> +		if (domain->has_iotlb_device)
>> +			continue;
>> +
>> +		nested_flush_dev_iotlb(domain, addr, mask, &fault);
>> +		if (fault & (DMA_FSTS_ITE | DMA_FSTS_ICE))
>> +			break;
> 
> here you may add a note that we don't plan to forward invalidation
> queue error (i.e. IQE) to the caller as it's caused only by driver
> internal bug.

yes.

> 
>> +
>> +		if (!IS_ALIGNED(inv_entry.addr, VTD_PAGE_SIZE) ||
>> +		    ((inv_entry.npages == U64_MAX) && inv_entry.addr)) {
>> +			ret = -EINVAL;
>> +			break;
>> +		}
>> +
> 
> why is [non-zero-addr, U64_MAX] an error? Is it explicitly stated to
> be not supported by underlying helpers?

no such limitation by underlying helpers. But in such case, the 
addr+npages*PAGE_SIZE would exceed U64_MAX, this seems a bit
strange. But I'm fine to relax the check since the underlying helper
only checks npages when determining paid-selective or not.

-- 
Regards,
Yi Liu