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iommu/vt-d: Use bitfields for DMAR capabilities

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IOTLB device presence, iommu coherency and snooping are boolean
capabilities. Use them as bits and keep them adjacent.

Structure layout before the reorg.
$ pahole -C dmar_domain drivers/iommu/intel/dmar.o
struct dmar_domain {
        int                        nid;                  /*     0     4 */
        unsigned int               iommu_refcnt[128];    /*     4   512 */
        /* --- cacheline 8 boundary (512 bytes) was 4 bytes ago --- */
        u16                        iommu_did[128];       /*   516   256 */
        /* --- cacheline 12 boundary (768 bytes) was 4 bytes ago --- */
        bool                       has_iotlb_device;     /*   772     1 */

        /* XXX 3 bytes hole, try to pack */

        struct list_head           devices;              /*   776    16 */
        struct list_head           subdevices;           /*   792    16 */
        struct iova_domain         iovad __attribute__((__aligned__(8)));
							 /*   808  2320 */
        /* --- cacheline 48 boundary (3072 bytes) was 56 bytes ago --- */
        struct dma_pte *           pgd;                  /*  3128     8 */
        /* --- cacheline 49 boundary (3136 bytes) --- */
        int                        gaw;                  /*  3136     4 */
        int                        agaw;                 /*  3140     4 */
        int                        flags;                /*  3144     4 */
        int                        iommu_coherency;      /*  3148     4 */
        int                        iommu_snooping;       /*  3152     4 */
        int                        iommu_count;          /*  3156     4 */
        int                        iommu_superpage;      /*  3160     4 */

        /* XXX 4 bytes hole, try to pack */

        u64                        max_addr;             /*  3168     8 */
        u32                        default_pasid;        /*  3176     4 */

        /* XXX 4 bytes hole, try to pack */

        struct iommu_domain        domain;               /*  3184    72 */

        /* size: 3256, cachelines: 51, members: 18 */
        /* sum members: 3245, holes: 3, sum holes: 11 */
        /* forced alignments: 1 */
        /* last cacheline: 56 bytes */
} __attribute__((__aligned__(8)));

After arranging it for natural padding and to make flags as u8 bits, it
saves 8 bytes for the struct.

struct dmar_domain {
        int                        nid;                  /*     0     4 */
        unsigned int               iommu_refcnt[128];    /*     4   512 */
        /* --- cacheline 8 boundary (512 bytes) was 4 bytes ago --- */
        u16                        iommu_did[128];       /*   516   256 */
        /* --- cacheline 12 boundary (768 bytes) was 4 bytes ago --- */
        u8                         has_iotlb_device:1;   /*   772: 0  1 */
        u8                         iommu_coherency:1;    /*   772: 1  1 */
        u8                         iommu_snooping:1;     /*   772: 2  1 */

        /* XXX 5 bits hole, try to pack */
        /* XXX 3 bytes hole, try to pack */

        struct list_head           devices;              /*   776    16 */
        struct list_head           subdevices;           /*   792    16 */
        struct iova_domain         iovad __attribute__((__aligned__(8)));
							 /*   808  2320 */
        /* --- cacheline 48 boundary (3072 bytes) was 56 bytes ago --- */
        struct dma_pte *           pgd;                  /*  3128     8 */
        /* --- cacheline 49 boundary (3136 bytes) --- */
        int                        gaw;                  /*  3136     4 */
        int                        agaw;                 /*  3140     4 */
        int                        flags;                /*  3144     4 */
        int                        iommu_count;          /*  3148     4 */
        int                        iommu_superpage;      /*  3152     4 */

        /* XXX 4 bytes hole, try to pack */

        u64                        max_addr;             /*  3160     8 */
        u32                        default_pasid;        /*  3168     4 */

        /* XXX 4 bytes hole, try to pack */

        struct iommu_domain        domain;               /*  3176    72 */

        /* size: 3248, cachelines: 51, members: 18 */
        /* sum members: 3236, holes: 3, sum holes: 11 */
        /* sum bitfield members: 3 bits, bit holes: 1, sum bit holes: 5 bits */
        /* forced alignments: 1 */
        /* last cacheline: 48 bytes */
} __attribute__((__aligned__(8)));

Signed-off-by: Parav Pandit <parav@nvidia.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20210530075053.264218-1-parav@nvidia.com
Link: https://lore.kernel.org/r/20210610020115.1637656-20-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Parav Pandit 2021-06-10 10:01:11 +08:00 • committed by Joerg Roedel
parent 3bc770b0e9
commit 1f106ff0ea
2 changed files with 13 additions and 13 deletions
Download patch file Download diff file Expand all files Collapse all files

8
include/linux/intel-iommu.h
View file

@ -546,7 +546,10 @@ struct dmar_domain {
* domain ids are 16 bit wide according
* to VT-d spec, section 9.3 */
bool has_iotlb_device;
u8 has_iotlb_device: 1;
u8 iommu_coherency: 1; /* indicate coherency of iommu access */
u8 iommu_snooping: 1; /* indicate snooping control feature */
struct list_head devices; /* all devices' list */
struct list_head subdevices; /* all subdevices' list */
struct iova_domain iovad; /* iova's that belong to this domain */
@ -558,9 +561,6 @@ struct dmar_domain {
int agaw;
int flags; /* flags to find out type of domain */
int iommu_coherency;/* indicate coherency of iommu access */
int iommu_snooping; /* indicate snooping control feature*/
int iommu_count; /* reference count of iommu */
int iommu_superpage;/* Level of superpages supported:
0 == 4KiB (no superpages), 1 == 2MiB,