Re: [PATCH] MdeModulePkg: ScsiDiskDxe: fix to support EFI_ERASE_BLOCK_PROTOCOL

[Paolo Bonzini <pbonzini@redhat.com>]

On 15/04/2017 15:44, Haojian Zhuang wrote:
> If bit TPZ and bit TPRZ are set, the erase feature is implemented.
> If bit TPZ is set and bit TPRZ is clear, the discard feature is
> implemented. And discard is a non-secure variant of the erase
> functionality.
> 
> So the detecting operation of EFI_ERASE_BLOCK_PROTOCOL, we should
> consider to support both functionality. Since discard functionality is
> only supported in some UFS devices.
> 
> And both of these two features are relied on UNMAP command.

Hi,

you need to use WRITE SAME, with a zero payload and the UNMAP bit set in
the command descriptor, in order to achieve a "secure" erase
functionality.  UNMAP is only an advisory command, and does not
guarantee that the blocks are unmapped.

Discard can use either WRITE SAME or UNMAP.

Also,

>      // Bits TPE and TPRZ should both be set to enable the erase feature on UFS.
> +    // Setting bit TPE and clearing bit TPRZ to enable the discard feature on UFS.
>      //
> -    if (((CapacityData16->LowestAlignLogic2 & BIT7) == 0) ||
> -        ((CapacityData16->LowestAlignLogic2 & BIT6) == 0)) {
> +    if ((CapacityData16->LowestAlignLogic2 & BIT7) == 0) {
>        DEBUG ((
>          EFI_D_VERBOSE,
>          "ScsiDisk EraseBlock: Either TPE or TPRZ is not set: 0x%x.\n",

The debug message is now wrong.

Paolo