Re: [PATCH V10 05/11] iommu/vt-d: Add nested translation helper function

Auger Eric
2020-03-29T11:35:47Z

Hi Jacob,

On 3/21/20 12:27 AM, Jacob Pan wrote:
> Nested translation mode is supported in VT-d 3.0 Spec.CH 3.8.
> With PASID granular translation type set to 0x11b, translation
> result from the first level(FL) also subject to a second level(SL)
> page table translation. This mode is used for SVA virtualization,
> where FL performs guest virtual to guest physical translation and
> SL performs guest physical to host physical translation.
>
> This patch adds a helper function for setting up nested translation
> where second level comes from a domain and first level comes from
> a guest PGD.
>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Signed-off-by: Liu, Yi L <yi.l.liu@linux.intel.com>
> ---
> drivers/iommu/intel-pasid.c | 240 +++++++++++++++++++++++++++++++++++++++++++-
> drivers/iommu/intel-pasid.h | 12 +++
> include/linux/intel-iommu.h | 3 +
> 3 files changed, 252 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iommu/intel-pasid.c b/drivers/iommu/intel-pasid.c
> index 9bdb7ee228b6..10c7856afc6b 100644
> --- a/drivers/iommu/intel-pasid.c
> +++ b/drivers/iommu/intel-pasid.c
> @@ -359,6 +359,76 @@ pasid_set_flpm(struct pasid_entry *pe, u64 value)
> pasid_set_bits(&pe->val[2], GENMASK_ULL(3, 2), value << 2);
> }
>
> +/*
> + * Setup the Extended Memory Type(EMT) field (Bits 91-93)
> + * of a scalable mode PASID entry.
> + */
> +static inline void
> +pasid_set_emt(struct pasid_entry *pe, u64 value)
> +{
> + pasid_set_bits(&pe->val[1], GENMASK_ULL(29, 27), value << 27);
> +}
> +
> +/*
> + * Setup the Page Attribute Table (PAT) field (Bits 96-127)
> + * of a scalable mode PASID entry.
> + */
> +static inline void
> +pasid_set_pat(struct pasid_entry *pe, u64 value)
> +{
> + pasid_set_bits(&pe->val[1], GENMASK_ULL(63, 32), value << 32);
> +}
> +
> +/*
> + * Setup the Cache Disable (CD) field (Bit 89)
> + * of a scalable mode PASID entry.
> + */
> +static inline void
> +pasid_set_cd(struct pasid_entry *pe)
> +{
> + pasid_set_bits(&pe->val[1], 1 << 25, 1 << 25);
> +}
> +
> +/*
> + * Setup the Extended Memory Type Enable (EMTE) field (Bit 90)
> + * of a scalable mode PASID entry.
> + */
> +static inline void
> +pasid_set_emte(struct pasid_entry *pe)
> +{
> + pasid_set_bits(&pe->val[1], 1 << 26, 1 << 26);
> +}
> +
> +/*
> + * Setup the Extended Access Flag Enable (EAFE) field (Bit 135)
> + * of a scalable mode PASID entry.
> + */
> +static inline void
> +pasid_set_eafe(struct pasid_entry *pe)
> +{
> + pasid_set_bits(&pe->val[2], 1 << 7, 1 << 7);
> +}
> +
> +/*
> + * Setup the Page-level Cache Disable (PCD) field (Bit 95)
> + * of a scalable mode PASID entry.
> + */
> +static inline void
> +pasid_set_pcd(struct pasid_entry *pe)
> +{
> + pasid_set_bits(&pe->val[1], 1 << 31, 1 << 31);
> +}
> +
> +/*
> + * Setup the Page-level Write-Through (PWT)) field (Bit 94)
> + * of a scalable mode PASID entry.
> + */
> +static inline void
> +pasid_set_pwt(struct pasid_entry *pe)
> +{
> + pasid_set_bits(&pe->val[1], 1 << 30, 1 << 30);
> +}
> +
> static void
> pasid_cache_invalidation_with_pasid(struct intel_iommu *iommu,
> u16 did, int pasid)
> @@ -492,7 +562,7 @@ int intel_pasid_setup_first_level(struct intel_iommu *iommu,
> pasid_set_page_snoop(pte, !!ecap_smpwc(iommu->ecap));
>
> /* Setup Present and PASID Granular Transfer Type: */
> - pasid_set_translation_type(pte, 1);
> + pasid_set_translation_type(pte, PASID_ENTRY_PGTT_FL_ONLY);
> pasid_set_present(pte);
> pasid_flush_caches(iommu, pte, pasid, did);
>
> @@ -564,7 +634,7 @@ int intel_pasid_setup_second_level(struct intel_iommu *iommu,
> pasid_set_domain_id(pte, did);
> pasid_set_slptr(pte, pgd_val);
> pasid_set_address_width(pte, agaw);
> - pasid_set_translation_type(pte, 2);
> + pasid_set_translation_type(pte, PASID_ENTRY_PGTT_SL_ONLY);
> pasid_set_fault_enable(pte);
> pasid_set_page_snoop(pte, !!ecap_smpwc(iommu->ecap));
>
> @@ -598,7 +668,7 @@ int intel_pasid_setup_pass_through(struct intel_iommu *iommu,
> pasid_clear_entry(pte);
> pasid_set_domain_id(pte, did);
> pasid_set_address_width(pte, iommu->agaw);
> - pasid_set_translation_type(pte, 4);
> + pasid_set_translation_type(pte, PASID_ENTRY_PGTT_PT);
> pasid_set_fault_enable(pte);
> pasid_set_page_snoop(pte, !!ecap_smpwc(iommu->ecap));

All above looks good to me
>
> @@ -612,3 +682,167 @@ int intel_pasid_setup_pass_through(struct intel_iommu *iommu,
>
> return 0;
> }
> +
> +static int intel_pasid_setup_bind_data(struct intel_iommu *iommu,
> + struct pasid_entry *pte,
> + struct iommu_gpasid_bind_data_vtd *pasid_data)
> +{
> + /*
> + * Not all guest PASID table entry fields are passed down during bind,
> + * here we only set up the ones that are dependent on guest settings.
> + * Execution related bits such as NXE, SMEP are not meaningful to IOMMU,
> + * therefore not set. Other fields, such as snoop related, are set based
> + * on host needs regardless of guest settings.
> + */
> + if (pasid_data->flags & IOMMU_SVA_VTD_GPASID_SRE) {
> + if (!ecap_srs(iommu->ecap)) {
> + pr_err("No supervisor request support on %s\n",
> + iommu->name);
> + return -EINVAL;
> + }
> + pasid_set_sre(pte);
> + }
> +
> + if (pasid_data->flags & IOMMU_SVA_VTD_GPASID_EAFE) {
> + if (!ecap_eafs(iommu->ecap)) {
> + pr_err("No extended access flag support on %s\n",
> + iommu->name);
> + return -EINVAL;
> + }
> + pasid_set_eafe(pte);
> + }
> +
> + /*
> + * Memory type is only applicable to devices inside processor coherent
> + * domain. PCIe devices are not included. We can skip the rest of the
> + * flags if IOMMU does not support MTS.
> + */
nit:
if (!pasid_data->flags & IOMMU_SVA_VTD_GPASID_MTS_MASK)
return 0;

if (!ecap_mts(iommu->ecap) {
pr_err("No memory type support for bind guest PASID on %s\n",
iommu->name);
return -EINVAL;
}

settings ../..
> + if (ecap_mts(iommu->ecap)) {
> + if (pasid_data->flags & IOMMU_SVA_VTD_GPASID_EMTE) {
> + pasid_set_emte(pte);
> + pasid_set_emt(pte, pasid_data->emt);
> + }
> + if (pasid_data->flags & IOMMU_SVA_VTD_GPASID_PCD)
> + pasid_set_pcd(pte);
> + if (pasid_data->flags & IOMMU_SVA_VTD_GPASID_PWT)
> + pasid_set_pwt(pte);
> + if (pasid_data->flags & IOMMU_SVA_VTD_GPASID_CD)
> + pasid_set_cd(pte);
> + pasid_set_pat(pte, pasid_data->pat);
> + } else if (pasid_data->flags & IOMMU_SVA_VTD_GPASID_MTS_MASK) {
> + pr_err("No memory type support for bind guest PASID on %s\n",
> + iommu->name);
> + return -EINVAL;
> + }
> +
> + return 0;
> +
> +}
> +
> +/**
> + * intel_pasid_setup_nested() - Set up PASID entry for nested translation.
> + * This could be used for guest shared virtual address. In this case, the
> + * first level page tables are used for GVA-GPA translation in the guest,
> + * second level page tables are used for GPA-HPA translation.
> + *
> + * @iommu: IOMMU which the device belong to
> + * @dev: Device to be set up for translation
> + * @gpgd: FLPTPTR: First Level Page translation pointer in GPA
> + * @pasid: PASID to be programmed in the device PASID table
> + * @pasid_data: Additional PASID info from the guest bind request
> + * @domain: Domain info for setting up second level page tables
> + * @addr_width: Address width of the first level (guest)
> + */
> +int intel_pasid_setup_nested(struct intel_iommu *iommu,
> + struct device *dev, pgd_t *gpgd,
> + int pasid, struct iommu_gpasid_bind_data_vtd *pasid_data,
> + struct dmar_domain *domain,
> + int addr_width)
> +{
> + struct pasid_entry *pte;
> + struct dma_pte *pgd;
> + int ret = 0;
> + u64 pgd_val;
> + int agaw;
> + u16 did;
> +
> + if (!ecap_nest(iommu->ecap)) {
> + pr_err("IOMMU: %s: No nested translation support\n",
> + iommu->name);
> + return -EINVAL;
> + }
I am surprised you don't check that the dmar_domain has the
DOMAIN_FLAG_NESTED_MODE flag (ir I missed it). Don't you have any risk
that the userspace overwrites the PTE of a device attached to an usual
domain, ie. fulled handled by the host?
> +
> + pte = intel_pasid_get_entry(dev, pasid);
> + if (WARN_ON(!pte))
> + return -EINVAL;
> +
> + /*
> + * Caller must ensure PASID entry is not in use, i.e. not bind the
> + * same PASID to the same device twice.
> + */
> + if (pasid_pte_is_present(pte))
> + return -EBUSY;
Here you check the PTE is not valid, is it sufficient to guarantee the
above? Also refering to the race potential issue pointed out by Kevin.
> +
> + pasid_clear_entry(pte);
> +
> + /* Sanity checking performed by caller to make sure address
> + * width matching in two dimensions:
> + * 1. CPU vs. IOMMU
> + * 2. Guest vs. Host.
> + */
> + switch (addr_width) {
> + case ADDR_WIDTH_5LEVEL:
> + if (cpu_feature_enabled(X86_FEATURE_LA57) &&
> + cap_5lp_support(iommu->cap)) {
> + pasid_set_flpm(pte, 1);
> + } else {
> + dev_err(dev, "5-level paging not supported\n");
> + return -EINVAL;
> + }
> + break;
> + case ADDR_WIDTH_4LEVEL:
> + pasid_set_flpm(pte, 0);
> + break;
> + default:
> + dev_err(dev, "Invalid guest address width %d\n", addr_width);
> + return -EINVAL;
> + }
> +
> + /* First level PGD is in GPA, must be supported by the second level */
> + if ((u64)gpgd > domain->max_addr) {
> + dev_err(dev, "Guest PGD %llx not supported, max %llx\n",
> + (u64)gpgd, domain->max_addr);
> + return -EINVAL;
> + }
> + pasid_set_flptr(pte, (u64)gpgd);
> +
> + ret = intel_pasid_setup_bind_data(iommu, pte, pasid_data);
> + if (ret) {
> + dev_err(dev, "Guest PASID bind data not supported\n");
Shall we output all those traces without limit? They are triggered by
userspace, meaning this latter can trigger a storm of those.
> + return ret;
> + }
> +
> + /* Setup the second level based on the given domain */
> + pgd = domain->pgd;
> +
> + agaw = iommu_skip_agaw(domain, iommu, &pgd);
> + if (agaw < 0) {
> + dev_err(dev, "Invalid domain page table\n");
> + return -EINVAL;
> + }
> + pgd_val = virt_to_phys(pgd);
> + pasid_set_slptr(pte, pgd_val);
> + pasid_set_fault_enable(pte);
> +
> + did = domain->iommu_did[iommu->seq_id];
> + pasid_set_domain_id(pte, did);
> +
> + pasid_set_address_width(pte, agaw);
> + pasid_set_page_snoop(pte, !!ecap_smpwc(iommu->ecap));
> +
> + pasid_set_translation_type(pte, PASID_ENTRY_PGTT_NESTED);
> + pasid_set_present(pte);
> + pasid_flush_caches(iommu, pte, pasid, did);
> +
> + return ret;
> +}
> diff --git a/drivers/iommu/intel-pasid.h b/drivers/iommu/intel-pasid.h
> index 92de6df24ccb..698015ee3f04 100644
> --- a/drivers/iommu/intel-pasid.h
> +++ b/drivers/iommu/intel-pasid.h
> @@ -36,6 +36,7 @@
> * to vmalloc or even module mappings.
> */
> #define PASID_FLAG_SUPERVISOR_MODE BIT(0)
> +#define PASID_FLAG_NESTED BIT(1)
>
> /*
> * The PASID_FLAG_FL5LP flag Indicates using 5-level paging for first-
> @@ -51,6 +52,11 @@ struct pasid_entry {
> u64 val[8];
> };
>
> +#define PASID_ENTRY_PGTT_FL_ONLY (1)
> +#define PASID_ENTRY_PGTT_SL_ONLY (2)
> +#define PASID_ENTRY_PGTT_NESTED (3)
> +#define PASID_ENTRY_PGTT_PT (4)
> +
> /* The representative of a PASID table */
> struct pasid_table {
> void *table; /* pasid table pointer */
> @@ -99,6 +105,12 @@ int intel_pasid_setup_second_level(struct intel_iommu *iommu,
> int intel_pasid_setup_pass_through(struct intel_iommu *iommu,
> struct dmar_domain *domain,
> struct device *dev, int pasid);
> +int intel_pasid_setup_nested(struct intel_iommu *iommu,
> + struct device *dev, pgd_t *pgd,
> + int pasid,
> + struct iommu_gpasid_bind_data_vtd *pasid_data,
> + struct dmar_domain *domain,
> + int addr_width);
> void intel_pasid_tear_down_entry(struct intel_iommu *iommu,
> struct device *dev, int pasid);
>
> diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
> index ed7171d2ae1f..eda1d6687144 100644
> --- a/include/linux/intel-iommu.h
> +++ b/include/linux/intel-iommu.h
> @@ -42,6 +42,9 @@
> #define DMA_FL_PTE_PRESENT BIT_ULL(0)
> #define DMA_FL_PTE_XD BIT_ULL(63)
>
> +#define ADDR_WIDTH_5LEVEL (57)
> +#define ADDR_WIDTH_4LEVEL (48)
> +
> #define CONTEXT_TT_MULTI_LEVEL 0
> #define CONTEXT_TT_DEV_IOTLB 1
> #define CONTEXT_TT_PASS_THROUGH 2
>
Thanks

Eric