Re: [PATCH] ide: Cap LBA28 capacity announcement to 2^28-1

[Samuel Thibault]

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Samuel Thibault, le mar. 24 août 2021 12:43:44 +0200, a ecrit:
> The LBA28 capacity (at offsets 60/61 of identification) is supposed to
> express the maximum size supported by LBA28 commands. If the device is
> larger than this, we have to cap it to 2^28-1.
> 
> At least NetBSD happens to be using this value to determine whether to use
> LBA28 or LBA48 for its commands, using LBA28 for sectors that don't need
> LBA48. This commit thus fixes NetBSD access to disks larger than 128GiB.
> 
> Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
> ---
>  hw/ide/core.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/ide/core.c b/hw/ide/core.c
> index fd69ca3167..e28f8aad61 100644
> --- a/hw/ide/core.c
> +++ b/hw/ide/core.c
> @@ -98,8 +98,12 @@ static void put_le16(uint16_t *p, unsigned int v)
>  static void ide_identify_size(IDEState *s)
>  {
>      uint16_t *p = (uint16_t *)s->identify_data;
> -    put_le16(p + 60, s->nb_sectors);
> -    put_le16(p + 61, s->nb_sectors >> 16);
> +    int64_t nb_sectors_lba28 = s->nb_sectors;
> +    if (nb_sectors_lba28 >= 1 << 28) {
> +        nb_sectors_lba28 = (1 << 28) - 1;
> +    }
> +    put_le16(p + 60, nb_sectors_lba28);
> +    put_le16(p + 61, nb_sectors_lba28 >> 16);
>      put_le16(p + 100, s->nb_sectors);
>      put_le16(p + 101, s->nb_sectors >> 16);
>      put_le16(p + 102, s->nb_sectors >> 32);
> -- 
> 2.32.0
>