Re: [PATCH rfcv2 06/17] intel_iommu: Implement stage-1 translation

[CLEMENT MATHIEU--DRIF]

Hi Zhenzhong,

I already sent you my comments about this patch earlier (question about 
checking pgtt) but here is a style review

On 22/05/2024 08:23, Zhenzhong Duan wrote:
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>
> From: Yi Liu <yi.l.liu@intel.com>
>
> This adds stage-1 page table walking to support stage-1 only
> transltion in scalable modern mode.
>
> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> Signed-off-by: Yi Sun <yi.y.sun@linux.intel.com>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> ---
>   hw/i386/intel_iommu_internal.h |  17 +++++
>   hw/i386/intel_iommu.c          | 128 +++++++++++++++++++++++++++++++--
>   2 files changed, 141 insertions(+), 4 deletions(-)
>
> diff --git a/hw/i386/intel_iommu_internal.h b/hw/i386/intel_iommu_internal.h
> index 0e240d6d54..abfdbd5f65 100644
> --- a/hw/i386/intel_iommu_internal.h
> +++ b/hw/i386/intel_iommu_internal.h
> @@ -534,6 +534,23 @@ typedef struct VTDRootEntry VTDRootEntry;
>   #define VTD_SM_PASID_ENTRY_AW          7ULL /* Adjusted guest-address-width 
> */
>   #define VTD_SM_PASID_ENTRY_DID(val)    ((val) & VTD_DOMAIN_ID_MASK)
>
> +#define VTD_SM_PASID_ENTRY_FLPM          3ULL
> +#define VTD_SM_PASID_ENTRY_FLPTPTR       (~0xfffULL)
> +
> +/* Paging Structure common */
> +#define VTD_FL_PT_PAGE_SIZE_MASK    (1ULL << 7)
> +/* Bits to decide the offset for each level */
> +#define VTD_FL_LEVEL_BITS           9
> +
> +/* First Level Paging Structure */
> +#define VTD_FL_PT_LEVEL             1
> +#define VTD_FL_PT_ENTRY_NR          512
> +
> +/* Masks for First Level Paging Entry */
> +#define VTD_FL_RW_MASK              (1ULL << 1)
> +#define VTD_FL_PT_BASE_ADDR_MASK(aw) (~(VTD_PAGE_SIZE - 1) & 
> VTD_HAW_MASK(aw))
> +#define VTD_PASID_ENTRY_FPD         (1ULL << 1) /* Fault Processing Disable 
> */
> +
>   /* Second Level Page Translation Pointer*/
>   #define VTD_SM_PASID_ENTRY_SLPTPTR     (~0xfffULL)
>
> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> index 544e8f0e40..cf29809bc1 100644
> --- a/hw/i386/intel_iommu.c
> +++ b/hw/i386/intel_iommu.c
> @@ -50,6 +50,8 @@
>   /* pe operations */
>   #define VTD_PE_GET_TYPE(pe) ((pe)->val[0] & VTD_SM_PASID_ENTRY_PGTT)
>   #define VTD_PE_GET_LEVEL(pe) (2 + (((pe)->val[0] >> 2) & 
> VTD_SM_PASID_ENTRY_AW))
> +#define VTD_PE_GET_FLPT_LEVEL(pe) \
> +    (4 + (((pe)->val[2] >> 2) & VTD_SM_PASID_ENTRY_FLPM))
>
>   /*
>    * PCI bus number (or SID) is not reliable since the device is usaully
> @@ -823,6 +825,11 @@ static int 
> vtd_get_pe_in_pasid_leaf_table(IntelIOMMUState *s,
>               return -VTD_FR_PASID_TABLE_ENTRY_INV;
>       }
>
> +    if (pgtt == VTD_SM_PASID_ENTRY_FLT &&
> +        VTD_PE_GET_FLPT_LEVEL(pe) != 4) {
Maybe you could add a function to check if the level is supported.
And it would also be nice to rename vtd_is_level_supported (used just 
above these lines) to make it clear that it's only relevant for second 
level translations and avoid mistakes
> +            return -VTD_FR_PASID_TABLE_ENTRY_INV;
> +    }
> +
>       return 0;
>   }
>
> @@ -958,7 +965,11 @@ static uint32_t vtd_get_iova_level(IntelIOMMUState *s,
>
>       if (s->root_scalable) {
>           vtd_ce_get_rid2pasid_entry(s, ce, &pe, pasid);
> -        return VTD_PE_GET_LEVEL(&pe);
> +        if (s->scalable_modern) {
> +            return VTD_PE_GET_FLPT_LEVEL(&pe);
> +        } else {
> +            return VTD_PE_GET_LEVEL(&pe);
same, could be renamed
> +        }
>       }
>
>       return vtd_ce_get_level(ce);
> @@ -1045,7 +1056,11 @@ static dma_addr_t 
> vtd_get_iova_pgtbl_base(IntelIOMMUState *s,
>
>       if (s->root_scalable) {
>           vtd_ce_get_rid2pasid_entry(s, ce, &pe, pasid);
> -        return pe.val[0] & VTD_SM_PASID_ENTRY_SLPTPTR;
> +        if (s->scalable_modern) {
> +            return pe.val[2] & VTD_SM_PASID_ENTRY_FLPTPTR;
> +        } else {
> +            return pe.val[0] & VTD_SM_PASID_ENTRY_SLPTPTR;
> +        }
>       }
>
>       return vtd_ce_get_slpt_base(ce);
> @@ -1847,6 +1862,106 @@ out:
>       trace_vtd_pt_enable_fast_path(source_id, success);
>   }
>
> +/* The shift of an addr for a certain level of paging structure */
> +static inline uint32_t vtd_flpt_level_shift(uint32_t level)
> +{
> +    assert(level != 0);
> +    return VTD_PAGE_SHIFT_4K + (level - 1) * VTD_FL_LEVEL_BITS;
> +}
> +
> +/*
> + * Given an iova and the level of paging structure, return the offset
> + * of current level.
> + */
> +static inline uint32_t vtd_iova_fl_level_offset(uint64_t iova, uint32_t 
> level)
> +{
> +    return (iova >> vtd_flpt_level_shift(level)) &
> +            ((1ULL << VTD_FL_LEVEL_BITS) - 1);
> +}
> +
> +/* Get the content of a flpte located in @base_addr[@index] */
> +static uint64_t vtd_get_flpte(dma_addr_t base_addr, uint32_t index)
> +{
> +    uint64_t flpte;
> +
> +    assert(index < VTD_FL_PT_ENTRY_NR);
> +
> +    if (dma_memory_read(&address_space_memory,
> +                        base_addr + index * sizeof(flpte), &flpte,
> +                        sizeof(flpte), MEMTXATTRS_UNSPECIFIED)) {
> +        flpte = (uint64_t)-1;
> +        return flpte;
> +    }
> +    flpte = le64_to_cpu(flpte);
> +    return flpte;
> +}
> +
> +static inline bool vtd_flpte_present(uint64_t flpte)
> +{
> +    return !!(flpte & 0x1);
Shouldn't we use a #define instead of hardcoding the mask?
> +}
> +
> +/* Whether the pte indicates the address of the page frame */
> +static inline bool vtd_is_last_flpte(uint64_t flpte, uint32_t level)
> +{
> +    return level == VTD_FL_PT_LEVEL || (flpte & VTD_FL_PT_PAGE_SIZE_MASK);
> +}
> +
> +static inline uint64_t vtd_get_flpte_addr(uint64_t flpte, uint8_t aw)
> +{
> +    return flpte & VTD_FL_PT_BASE_ADDR_MASK(aw);
> +}
> +
> +/*
> + * Given the @iova, get relevant @flptep. @flpte_level will be the last level
> + * of the translation, can be used for deciding the size of large page.
> + */
> +static int vtd_iova_to_flpte(IntelIOMMUState *s, VTDContextEntry *ce,
> +                             uint64_t iova, bool is_write,
> +                             uint64_t *flptep, uint32_t *flpte_level,
> +                             bool *reads, bool *writes, uint8_t aw_bits,
> +                             uint32_t pasid)
> +{
> +    dma_addr_t addr = vtd_get_iova_pgtbl_base(s, ce, pasid);
> +    uint32_t level = vtd_get_iova_level(s, ce, pasid);
> +    uint32_t offset;
> +    uint64_t flpte;
> +
> +    while (true) {
> +        offset = vtd_iova_fl_level_offset(iova, level);
> +        flpte = vtd_get_flpte(addr, offset);
> +        if (flpte == (uint64_t)-1) {
> +            if (level == vtd_get_iova_level(s, ce, pasid)) {
> +                /* Invalid programming of context-entry */
> +                return -VTD_FR_CONTEXT_ENTRY_INV;
> +            } else {
> +                return -VTD_FR_PAGING_ENTRY_INV;
> +            }
> +        }
> +
> +        if (!vtd_flpte_present(flpte)) {
> +            *reads = false;
> +            *writes = false;
> +            return -VTD_FR_PAGING_ENTRY_INV;
> +        }
> +
> +        *reads = true;
> +        *writes = (*writes) && (flpte & VTD_FL_RW_MASK);
> +        if (is_write && !(flpte & VTD_FL_RW_MASK)) {
> +            return -VTD_FR_WRITE;
> +        }
> +
> +        if (vtd_is_last_flpte(flpte, level)) {
> +            *flptep = flpte;
> +            *flpte_level = level;
> +            return 0;
> +        }
> +
> +        addr = vtd_get_flpte_addr(flpte, aw_bits);
> +        level--;
> +    }
> +}
> +
>   static void vtd_report_fault(IntelIOMMUState *s,
>                                int err, bool is_fpd_set,
>                                uint16_t source_id,
> @@ -1995,8 +2110,13 @@ static bool vtd_do_iommu_translate(VTDAddressSpace 
> *vtd_as, PCIBus *bus,
>           }
>       }
>
> -    ret_fr = vtd_iova_to_slpte(s, &ce, addr, is_write, &pte, &level,
> -                               &reads, &writes, s->aw_bits, pasid);
> +    if (s->scalable_modern) {
> +        ret_fr = vtd_iova_to_flpte(s, &ce, addr, is_write, &pte, &level,
> +                                   &reads, &writes, s->aw_bits, pasid);
> +    } else {
> +        ret_fr = vtd_iova_to_slpte(s, &ce, addr, is_write, &pte, &level,
> +                                   &reads, &writes, s->aw_bits, pasid);
> +    }
>
>       if (ret_fr) {
>           vtd_report_fault(s, -ret_fr, is_fpd_set, source_id,
> --
> 2.34.1
>
#cmd