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

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Message-ID: <b524d09e-62ea-41ca-904c-e9c94aef2b76@linux.intel.com>
Date: Wed, 23 Oct 2024 11:12:57 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Zhenzhong Duan <zhenzhong.duan@...el.com>, iommu@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Cc: baolu.lu@...ux.intel.com, dwmw2@...radead.org, joro@...tes.org,
 will@...nel.org, robin.murphy@....com, chao.p.peng@...el.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.

> ---
>   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?

> -	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