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Message-ID: <875D89B79D1D86448A583A7302C022A055AC01B4@G4W3212.americas.hpqcorp.net>
Date: Thu, 9 Jan 2014 21:13:36 +0000
From: "Sumner, William" <bill.sumner@...com>
To: Baoquan He <bhe@...hat.com>
CC: "dwmw2@...radead.org" <dwmw2@...radead.org>,
"indou.takao@...fujitsu.com" <indou.takao@...fujitsu.com>,
"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
"alex.williamson@...hat.com" <alex.williamson@...hat.com>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"ddutile@...hat.com" <ddutile@...hat.com>,
"ishii.hironobu@...fujitsu.com" <ishii.hironobu@...fujitsu.com>,
"bhelgaas@...gle.com" <bhelgaas@...gle.com>,
"Hatch, Douglas B (HPS Linux PM)" <doug.hatch@...com>
Subject: RE: [PATCHv2 4/6] Crashdump-Accepting-Active-IOMMU-Copy-Translations
Thank you for testing and reviewing this patch -- and for previously testing the RFC version of the patch.
I am currently preparing version 3 of the patch which will include your recommendations.
You mentioned two concerns in your email:
About this item:
...................................
> + INIT_LIST_HEAD(&domain->devices);
> + domain->id = (int) context_get_did(ce);
> + domain->agaw = (int) context_get_aw(ce);
> + domain->pgd = NULL;
Here the domain is created and initialized, but its member iovad is not
initialized. This will cause domain->iovad.iova_rbtree_lock deadlock
because its initial value is random. And the rbtree operation will
crash. This happen in reserve_iova invoked in copy_page_addr in high
frequency.
I add 1 line of code as below and it works well.
init_iova_domain(&domain->iovad, DMA_32BIT_PFN);
...................................
Yes, this line is necessary. I have added this line into the next version of the patch.
I also investigated why my earlier testing missed this. Looks like I was always getting zeroed memory which acts as though the structure is properly initialized for the fields of the structure that my code uses.
About this item: (And in your follow-up email about the same item)
.................................................
> > + ppap->page_addr = page_addr; /* Addr(new page) */
> > + ppap->page_size = page_size; /* Size(new page) */
> > +
> > + ppap->domain = domain; /* adr(domain for the new range) */
>
> Here I am confused, ppap is used to collect the copied ranges and
> necessary information. To my understanding, this domain is the
> dmar_domain which the 1st device is on. When ppat->last is set to 1,
> among the whole collected range, there may be many domains. I just feel
> not good for this. Is it OK to define a specific lock for ppap
> structure, possibly? Please correct me if I am wrong.
Well, check it again. It's not about the lock. Just all address is
recorded in one dmar_domain.
.................................................
Yes: no lock is required. This code operates only during Linux initialization when only one CPU is active.
Yes: ppap->domain holds the domain to be used when the address range accumulated in ppap->page_addr and ppap->page_size is eventually added to the tree (either when a new range is started or when ppap->last is set.)
Bill
-----Original Message-----
From: Baoquan He [mailto:bhe@...hat.com]
Sent: Friday, December 20, 2013 12:04 AM
To: Sumner, William
Cc: dwmw2@...radead.org; indou.takao@...fujitsu.com; iommu@...ts.linux-foundation.org; kexec@...ts.infradead.org; alex.williamson@...hat.com; linux-pci@...r.kernel.org; linux-kernel@...r.kernel.org; ddutile@...hat.com; ishii.hironobu@...fujitsu.com; bhelgaas@...gle.com; Hatch, Douglas B (HPS Linux PM)
Subject: Re: [PATCHv2 4/6] Crashdump-Accepting-Active-IOMMU-Copy-Translations
On 12/19/13 at 07:49pm, Bill Sumner wrote:
> +static int copy_page_addr(u64 page_addr, u32 shift, u32 bus, u32 devfn,
> + u64 pte, struct dmar_domain *domain,
> + void *parms)
> +{
> + struct copy_page_addr_parms *ppap = parms;
> +
> + u64 page_size = ((u64)1 << shift); /* page_size */
> + u64 pfn_lo; /* For reserving IOVA range */
> + u64 pfn_hi; /* For reserving IOVA range */
> + struct iova *iova_p; /* For reserving IOVA range */
> +
> + if (!ppap) {
> + pr_err("ERROR: ppap is NULL: 0x%3.3x(%3.3d) DevFn: 0x%3.3x(%3.3d) Page: 0x%16.16llx Size: 0x%16.16llx(%lld)\n",
> + bus, bus, devfn, devfn, page_addr,
> + page_size, page_size);
> + return 0;
> + }
> +
> + /* Prepare for a new page */
> + ppap->first = 0; /* Not first-time anymore */
> + ppap->bus = bus;
> + ppap->devfn = devfn;
> + ppap->shift = shift;
> + ppap->pte = pte;
> + ppap->next_addr = page_addr + page_size; /* Next-expected page_addr */
> +
> + ppap->page_addr = page_addr; /* Addr(new page) */
> + ppap->page_size = page_size; /* Size(new page) */
> +
> + ppap->domain = domain; /* adr(domain for the new range) */
Here I am confused, ppap is used to collect the copied ranges and
necessary information. To my understanding, this domain is the
dmar_domain which the 1st device is on. When ppat->last is set to 1,
among the whole collected range, there may be many domains. I just feel
not good for this. Is it OK to define a specific lock for ppap
structure, possibly? Please correct me if I am wrong.
> +
> + return 0;
> +}
> +
> +
> +
> +
> +static int copy_context_entry(struct intel_iommu *iommu, u32 bus, u32 devfn,
> + void *ppap, struct context_entry *ce)
> +{
> + int ret = 0; /* Integer Return Code */
> + u32 shift = 0; /* bits to shift page_addr */
> + u64 page_addr = 0; /* Address of translated page */
> + struct dma_pte *pgt_old_phys; /* Adr(page_table in the old kernel) */
> + struct dma_pte *pgt_new_phys; /* Adr(page_table in the new kernel) */
> + unsigned long asr; /* New asr value for new context */
> + u8 t; /* Translation-type from context */
> + u8 aw; /* Address-width from context */
> + u32 aw_shift[8] = {
> + 12+9+9, /* [000b] 30-bit AGAW (2-level page table) */
> + 12+9+9+9, /* [001b] 39-bit AGAW (3-level page table) */
> + 12+9+9+9+9, /* [010b] 48-bit AGAW (4-level page table) */
> + 12+9+9+9+9+9, /* [011b] 57-bit AGAW (5-level page table) */
> + 12+9+9+9+9+9+9, /* [100b] 64-bit AGAW (6-level page table) */
> + 0, /* [111b] Reserved */
> + 0, /* [110b] Reserved */
> + 0, /* [111b] Reserved */
> + };
> +
> + struct dmar_domain *domain = NULL; /* To hold domain & device */
> + /* values from old kernel */
> + struct device_domain_info *info = NULL; /* adr(new for this device) */
> + struct device_domain_info *i = NULL; /* iterator for foreach */
> +
> +
+ /* info->segment = segment; May need this later */
> + info->bus = bus;
> + info->devfn = devfn;
> + info->iommu = iommu;
> +
> + list_for_each_entry(i, &device_domain_values_list[iommu->seq_id],
> + global) {
> + if (i->domain->id == (int) context_get_did(ce)) {
> + domain = i->domain;
> + pr_debug("CTXT B:D:F:%2.2x:%2.2x:%1.1x Found did=0x%4.4x\n",
> + bus, devfn >> 3, devfn & 0x7, i->domain->id);
> + break;
> + }
> + }
> +
> + if (!domain) {
> + domain = alloc_domain();
> + if (!domain) {
> + ret = -ENOMEM;
> + goto exit;
> + }
> + INIT_LIST_HEAD(&domain->devices);
> + domain->id = (int) context_get_did(ce);
> + domain->agaw = (int) context_get_aw(ce);
> + domain->pgd = NULL;
Here the domain is created and initialized, but its member iovad is not
initialized. This will cause domain->iovad.iova_rbtree_lock deadlock
because its initial value is random. And the rbtree operation will
crash. This happen in reserve_iova invoked in copy_page_addr in high
frequency.
I add 1 line of code as below and it works well.
init_iova_domain(&domain->iovad, DMA_32BIT_PFN);
> +
> + pr_debug("CTXT Allocated new list entry, did:%d\n",
> + domain->id);
> + }
> +
> + info->domain = domain;
> + list_add(&info->link, &domain->devices);
> + list_add(&info->global, &device_domain_values_list[iommu->seq_id]);
> +
> + if (domain->pgd) {
> + asr = virt_to_phys(domain->pgd) >> VTD_PAGE_SHIFT;
> + context_put_asr(ce, asr);
> + ret = 4;
> + goto exit;
> + }
> +
> + t = context_get_t(ce);
> +
> + if (t == 0 || t == 1) { /* If (context has page tables) */
> + aw = context_get_aw(ce);
> + shift = aw_shift[aw];
> +
> + pgt_old_phys = (struct dma_pte *)(context_get_asr(ce) << 12);
> +
> + ret = copy_page_table(&pgt_new_phys, pgt_old_phys,
> + shift-9, page_addr, iommu, bus, devfn, domain, ppap);
> +
> + if (ret) /* if (problem) bail out */
> + goto exit;
> +
> + asr = ((unsigned long)(pgt_new_phys)) >> VTD_PAGE_SHIFT;
> + context_put_asr(ce, asr);
> + domain->pgd = phys_to_virt((unsigned long)pgt_new_phys);
> + ret = 1;
> + goto exit;
> + }
> +
> + return ret;
> +}
> +
--
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