linux-kernel - RE: [PATCH 1/2] iommu/vt-d: Fix checks in dmar_fault_dump

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Message-ID: <SJ0PR11MB6744E47FF944D4C576B6B973924D2@SJ0PR11MB6744.namprd11.prod.outlook.com>
Date: Wed, 23 Oct 2024 05:09:20 +0000
From: "Duan, Zhenzhong" <zhenzhong.duan@...el.com>
To: Baolu Lu <baolu.lu@...ux.intel.com>, "iommu@...ts.linux.dev"
	<iommu@...ts.linux.dev>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
CC: "dwmw2@...radead.org" <dwmw2@...radead.org>, "joro@...tes.org"
	<joro@...tes.org>, "will@...nel.org" <will@...nel.org>,
	"robin.murphy@....com" <robin.murphy@....com>, "Peng, Chao P"
	<chao.p.peng@...el.com>
Subject: RE: [PATCH 1/2] iommu/vt-d: Fix checks in dmar_fault_dump_ptes()



>-----Original Message-----
>From: Baolu Lu <baolu.lu@...ux.intel.com>
>Subject: Re: [PATCH 1/2] iommu/vt-d: Fix checks in dmar_fault_dump_ptes()
>
>On 2024/10/22 17:50, Zhenzhong Duan wrote:
>> In dmar_fault_dump_ptes(), return value of phys_to_virt() is used for
>> checking if an entry is present. It's never NULL on x86 platform at least.
>> This makes some zero entries are dumped like below:
>>
>> [  442.240357] DMAR: pasid dir entry: 0x000000012c83e001
>> [  442.246661] DMAR: pasid table entry[0]: 0x0000000000000000
>> [  442.253429] DMAR: pasid table entry[1]: 0x0000000000000000
>> [  442.260203] DMAR: pasid table entry[2]: 0x0000000000000000
>> [  442.266969] DMAR: pasid table entry[3]: 0x0000000000000000
>> [  442.273733] DMAR: pasid table entry[4]: 0x0000000000000000
>> [  442.280479] DMAR: pasid table entry[5]: 0x0000000000000000
>> [  442.287234] DMAR: pasid table entry[6]: 0x0000000000000000
>> [  442.293989] DMAR: pasid table entry[7]: 0x0000000000000000
>> [  442.300742] DMAR: PTE not present at level 2
>>
>> Fix it by checking present bit in all entries.
>>
>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@...el.com>
>
>It seems that we still need a Fixes tag here.

OK, will add.

>
>> ---
>>   drivers/iommu/intel/iommu.c | 31 ++++++++++++++++++++-----------
>>   1 file changed, 20 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
>> index a564eeaf2375..8288b0ee7a61 100644
>> --- a/drivers/iommu/intel/iommu.c
>> +++ b/drivers/iommu/intel/iommu.c
>> @@ -733,12 +733,17 @@ void dmar_fault_dump_ptes(struct intel_iommu
>*iommu, u16 source_id,
>>   	u8 devfn = source_id & 0xff;
>>   	u8 bus = source_id >> 8;
>>   	struct dma_pte *pgtable;
>> +	u64 entry;
>>
>>   	pr_info("Dump %s table entries for IOVA 0x%llx\n", iommu->name, addr);
>>
>>   	/* root entry dump */
>>   	rt_entry = &iommu->root_entry[bus];
>> -	if (!rt_entry) {
>> +	entry = rt_entry->lo;
>> +	if (sm_supported(iommu) && devfn >= 0x80)
>> +		entry = rt_entry->hi;
>> +
>> +	if (!(entry & 1)) {
>>   		pr_info("root table entry is not present\n");
>>   		return;
>>   	}
>> @@ -766,28 +771,32 @@ void dmar_fault_dump_ptes(struct intel_iommu
>*iommu, u16 source_id,
>>   		goto pgtable_walk;
>>   	}
>>
>> +	/* For request-without-pasid, get the pasid from context entry */
>> +	if (pasid == IOMMU_PASID_INVALID)
>> +		pasid = IOMMU_NO_PASID;
>> +
>>   	/* get the pointer to pasid directory entry */
>>   	dir = phys_to_virt(ctx_entry->lo & VTD_PAGE_MASK);
>
>Is above code correct in the scalable mode?

I didn't find issue, could you show some light?

Thanks
Zhenzhong

>
>> -	if (!dir) {
>> +	dir_index = pasid >> PASID_PDE_SHIFT;
>> +	pde = &dir[dir_index];
>> +
>> +	if (!pasid_pde_is_present(pde)) {
>>   		pr_info("pasid directory entry is not present\n");
>>   		return;
>>   	}
>> -	/* For request-without-pasid, get the pasid from context entry */
>> -	if (intel_iommu_sm && pasid == IOMMU_PASID_INVALID)
>> -		pasid = IOMMU_NO_PASID;
>>
>> -	dir_index = pasid >> PASID_PDE_SHIFT;
>> -	pde = &dir[dir_index];
>>   	pr_info("pasid dir entry: 0x%016llx\n", pde->val);
>>
>>   	/* get the pointer to the pasid table entry */
>> -	entries = get_pasid_table_from_pde(pde);
>> -	if (!entries) {
>> +	entries = phys_to_virt(READ_ONCE(pde->val) & PDE_PFN_MASK);
>> +	index = pasid & PASID_PTE_MASK;
>> +	pte = &entries[index];
>> +
>> +	if (!pasid_pte_is_present(pte)) {
>>   		pr_info("pasid table entry is not present\n");
>>   		return;
>>   	}
>> -	index = pasid & PASID_PTE_MASK;
>> -	pte = &entries[index];
>> +
>>   	for (i = 0; i < ARRAY_SIZE(pte->val); i++)
>>   		pr_info("pasid table entry[%d]: 0x%016llx\n", i, pte->val[i]);
>>
>
>Thanks,
>baolu