Re: [PATCH v2 3/9] vfio/igd: canonicalize memory size calculations

[Corvin Köhne]

On Tue, 2024-12-03 at 21:35 +0800, Tomita Moeko wrote:
> CAUTION: External Email!!
> Add helper functions igd_gtt_memory_size() and igd_stolen_size() for
> calculating GTT stolen memory and Data stolen memory size in bytes,
> and use macros to replace the hardware-related magic numbers for
> better readability.
> 
> Signed-off-by: Tomita Moeko <tomitamoeko@gmail.com>
> ---
>  hw/vfio/igd.c | 99 ++++++++++++++++++++++++++++-----------------------
>  1 file changed, 55 insertions(+), 44 deletions(-)
> 
> diff --git a/hw/vfio/igd.c b/hw/vfio/igd.c
> index 2ede72d243..b5bfdc6580 100644
> --- a/hw/vfio/igd.c
> +++ b/hw/vfio/igd.c
> @@ -106,6 +106,51 @@ typedef struct VFIOIGDQuirk {
>  #define IGD_BDSM 0x5c /* Base Data of Stolen Memory */
>  #define IGD_BDSM_GEN11 0xc0 /* Base Data of Stolen Memory of gen 11 and later
> */
>  
> +#define IGD_GMCH_GEN6_GMS_SHIFT     3       /* SNB_GMCH in i915 */
> +#define IGD_GMCH_GEN6_GMS_MASK      0x1f
> +#define IGD_GMCH_GEN6_GGMS_SHIFT    8
> +#define IGD_GMCH_GEN6_GGMS_MASK     0x3
> +#define IGD_GMCH_GEN8_GMS_SHIFT     8       /* BDW_GMCH in i915 */
> +#define IGD_GMCH_GEN8_GMS_MASK      0xff
> +#define IGD_GMCH_GEN8_GGMS_SHIFT    6
> +#define IGD_GMCH_GEN8_GGMS_MASK     0x3
> +
> +static uint64_t igd_gtt_memory_size(int gen, uint16_t gmch)
> +{
> +    uint64_t ggms;
> +
> +    if (gen < 8) {
> +        ggms = (gmch >> IGD_GMCH_GEN6_GGMS_SHIFT) & IGD_GMCH_GEN6_GGMS_MASK;
> +    } else {
> +        ggms = (gmch >> IGD_GMCH_GEN8_GGMS_SHIFT) & IGD_GMCH_GEN8_GGMS_MASK;
> +        ggms *= 2;
> +    }
> +
> +    return ggms * MiB;
> +}
> +
> +static uint64_t igd_stolen_memory_size(int gen, uint32_t gmch)
> +{
> +    uint64_t gms;
> +
> +    if (gen < 8) {
> +        gms = (gmch >> IGD_GMCH_GEN6_GMS_SHIFT) & IGD_GMCH_GEN6_GMS_MASK;
> +    } else {
> +        gms = (gmch >> IGD_GMCH_GEN8_GMS_SHIFT) & IGD_GMCH_GEN8_GMS_MASK;
> +    }
> +
> +    if (gen < 9) {
> +            return gms * 32 * MiB;
> +    } else {
> +        if (gms < 0xf0) {
> +            return gms * 32 * MiB;
> +        } else {
> +            return (gms - 0xf0 + 1) * 4 * MiB;
> +        }
> +    }
> +
> +    return 0;
> +}
>  
>  /*
>   * The rather short list of registers that we copy from the host devices.
> @@ -254,17 +299,10 @@ static int vfio_pci_igd_lpc_init(VFIOPCIDevice *vdev,
>  static int vfio_igd_gtt_max(VFIOPCIDevice *vdev)
>  {
>      uint32_t gmch = vfio_pci_read_config(&vdev->pdev, IGD_GMCH,
> sizeof(gmch));
> -    int ggms, gen = igd_gen(vdev);
> -
> -    gmch = vfio_pci_read_config(&vdev->pdev, IGD_GMCH, sizeof(gmch));
> -    ggms = (gmch >> (gen < 8 ? 8 : 6)) & 0x3;
> -    if (gen >= 8) {
> -        ggms = 1 << ggms;
> -    }
> -
> -    ggms *= MiB;
> +    int gen = igd_gen(vdev);
> +    uint64_t ggms_size = igd_gtt_memory_size(gen, gmch);
>  
> -    return (ggms / (4 * KiB)) * (gen < 8 ? 4 : 8);
> +    return (ggms_size / (4 * KiB)) * (gen < 8 ? 4 : 8);
>  }
>  
>  /*
> @@ -471,30 +509,6 @@ void vfio_probe_igd_bar0_quirk(VFIOPCIDevice *vdev, int
> nr)
>      QLIST_INSERT_HEAD(&vdev->bars[nr].quirks, quirk, next);
>  }
>  
> -static int igd_get_stolen_mb(int gen, uint32_t gmch)
> -{
> -    int gms;
> -
> -    if (gen < 8) {
> -        gms = (gmch >> 3) & 0x1f;
> -    } else {
> -        gms = (gmch >> 8) & 0xff;
> -    }
> -
> -    if (gen < 9) {
> -        if (gms > 0x10) {
> -            error_report("Unsupported IGD GMS value 0x%x", gms);
> -            return 0;
> -        }
> -        return gms * 32;
> -    } else {
> -        if (gms < 0xf0)
> -            return gms * 32;
> -        else
> -            return (gms - 0xf0) * 4 + 4;
> -    }
> -}
> -
>  void vfio_probe_igd_bar4_quirk(VFIOPCIDevice *vdev, int nr)
>  {
>      g_autofree struct vfio_region_info *rom = NULL;
> @@ -504,7 +518,8 @@ void vfio_probe_igd_bar4_quirk(VFIOPCIDevice *vdev, int
> nr)
>      VFIOQuirk *quirk;
>      VFIOIGDQuirk *igd;
>      PCIDevice *lpc_bridge;
> -    int i, ret, ggms_mb, gms_mb = 0, gen;
> +    int i, ret, gen;
> +    uint64_t ggms_size, gms_size;
>      uint64_t *bdsm_size;
>      uint32_t gmch;
>      uint16_t cmd_orig, cmd;
> @@ -666,13 +681,8 @@ void vfio_probe_igd_bar4_quirk(VFIOPCIDevice *vdev, int
> nr)
>  
>      QLIST_INSERT_HEAD(&vdev->bars[nr].quirks, quirk, next);
>  
> -    /* Determine the size of stolen memory needed for GTT */
> -    ggms_mb = (gmch >> (gen < 8 ? 8 : 6)) & 0x3;
> -    if (gen >= 8) {
> -        ggms_mb = 1 << ggms_mb;
> -    }
> -
> -    gms_mb = igd_get_stolen_mb(gen, gmch);
> +    ggms_size = igd_gtt_memory_size(gen, gmch);
> +    gms_size = igd_stolen_memory_size(gen, gmch);
>  
>      /*
>       * Request reserved memory for stolen memory via fw_cfg.  VM firmware
> @@ -683,7 +693,7 @@ void vfio_probe_igd_bar4_quirk(VFIOPCIDevice *vdev, int
> nr)
>       * config offset 0x5C.
>       */
>      bdsm_size = g_malloc(sizeof(*bdsm_size));
> -    *bdsm_size = cpu_to_le64((ggms_mb + gms_mb) * MiB);
> +    *bdsm_size = cpu_to_le64(ggms_size + gms_size);
>      fw_cfg_add_file(fw_cfg_find(), "etc/igd-bdsm-size",
>                      bdsm_size, sizeof(*bdsm_size));
>  
> @@ -734,5 +744,6 @@ void vfio_probe_igd_bar4_quirk(VFIOPCIDevice *vdev, int
> nr)
>                       vdev-
> >https://nospamproxywebp.beckhoff.com/enQsig/link?id=BAgAAAADIUcZasZ36mwAAABM0
> 01Yig6LNmON7mS202pDuIRRNT-
> tIucgsQHKYe8WitBfoANcxBM2L6i4Sg4fLLMkXL_LDVUSEswEqsunuGsAr4DjgOogXtNMivhsyeaj9
> xYl9AgydV4QqrKMV29P7y3uAuqQcYz1GacVJRg1 );
>      }
>  
> -    trace_vfio_pci_igd_bdsm_enabled(vdev-
> >https://nospamproxywebp.beckhoff.com/enQsig/link?id=BAgAAAADIUcZasZ36mwAAABM0
> 01Yig6LNmON7mS202pDuIRRNT-
> tIucgsQHKYe8WitBfoANcxBM2L6i4Sg4fLLMkXL_LDVUSEswEqsunuGsAr4DjgOogXtNMivhsyeaj9
> xYl9AgydV4QqrKMV29P7y3uAuqQcYz1GacVJRg1 , ggms_mb + gms_mb);
> +    trace_vfio_pci_igd_bdsm_enabled(vdev-
> >https://nospamproxywebp.beckhoff.com/enQsig/link?id=BAgAAAADIUcZasZ36mwAAABM0
> 01Yig6LNmON7mS202pDuIRRNT-
> tIucgsQHKYe8WitBfoANcxBM2L6i4Sg4fLLMkXL_LDVUSEswEqsunuGsAr4DjgOogXtNMivhsyeaj9
> xYl9AgydV4QqrKMV29P7y3uAuqQcYz1GacVJRg1 ,
> +                                    (ggms_size + gms_size) / MiB);
>  }

Reviewed-by: Corvin Köhne <c.koehne@beckhoff.com>

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