[edk2-devel] ExtScsiPassThru support for Logical SCSI devices

Mon Jul 8 08:35:47 UTC 2019

Hi Hao Wu,

If a Controller supports both Logical and Physical Devices, as per spec we
need to create 2 instances.
1. Instance with EFI_EXT_SCSI_PASS_THRU_ATTRIBUTES_LOGICAL bit set.
2.  Instance with EFI_EXT_SCSI_PASS_THRU_ATTRIBUTES_PHYSICAL bit set.

And Each EFI_EXT_SCSI_PASS_THRU_PROTOCOL instance must have an associated
device path.

Now the issue is, The same GUID cannot be installed more than once onto the
same handle (Controller handle).
So to support 2nd instance we need to create new device path (virtual
device path) for that.

Once more issue is, how do we associate this newly created device path and
SCSI PassThru instance with actual controller . ?

*The logical protocol instance is used to produce media access protocols
(like BlockIO protocol). Some physical HW may not be visible/accessible
(e.g. HW used*

*for data backup, depending on the RAID configuration) by this logical
protocol instance. **The physical one is used to directly send commands to
all the managing devices.*

I dont think, because if any driver supports only Instance with
EFI_EXT_SCSI_PASS_THRU_ATTRIBUTES_PHYSICAL bit set, can't they create child
handles ??

As far as i know, Logical or Physical Instances are no where related to
media access protocols. Even without SCSI passthru protocol on controller
handle also, Block Io protocol can be installed on Controller Child
devices. (Its the uefi driver wish, how it passes commands to the Child's
of controller). Logical Instance is to interact with Logical Device and
Physical Instance is to interact with Physical devices as per spec.

*Users can always use the EFI Boot Service 'LocateHandleBuffer' to get all
the EFI_EXT_SCSI_PASS_THRU_PROTOCOL instances. Then, users can evaluate
each instance to see if it is the one they needed.*

Yes user can get the list of EFI_EXT_SCSI_PASS_THRU_PROTOCOL instances by
querying, but how the user can relate a particular instance with a
controller. ? Because the 2nd of SCSI PassThru is created on new device
path.(which will not have any other protocols, other than device path and
ext scsi pass thru).

Thanks,
Ravi Kumar

On Mon, Jul 8, 2019 at 8:39 AM Wu, Hao A <hao.a.wu at intel.com> wrote:

> Hello Ravi Kumar,
>
>
>
> May I know the specific issue you met when 2 ExtScsiPassThru instances are
>
> provided for the device?
>
>
>
> For some of your previous questions:
>
> ·         “Any background why EFI_EXT_SCSI_PASS_THRU_PROTOCOL needed 2
> instances ?”
>
> The logical protocol instance is used to produce media access protocols
> (like
>
> BlockIO protocol). Some physical HW may not be visible/accessible (e.g. HW
> used
>
> for data backup, depending on the RAID configuration) by this logical
> protocol
>
> instance.
>
>
>
> The physical one is used to directly send commands to all the managing
> devices.
>
>
>
> ·         “How User locates the Instance with
> EFI_EXT_SCSI_PASS_THRU_ATTRIBUTES_LOGICAL bit set and Instance with
> EFI_EXT_SCSI_PASS_THRU_ATTRIBUTES_PHYSICAL bit set. ??”
>
> Users can always use the EFI Boot Service 'LocateHandleBuffer' to get all
> the
>
> EFI_EXT_SCSI_PASS_THRU_PROTOCOL instances. Then, users can evaluate each
>
> instance to see if it is the one they needed.
>
>
>
> Best Regards,
>
> Hao Wu
>
>
>
> *From:* Ravi Kumar Siadri [mailto:siadriravikumaruefi at gmail.com]
> *Sent:* Sunday, July 07, 2019 2:58 PM
> *To:* Wu, Hao A; stephano
> *Cc:* devel at edk2.groups.io
> *Subject:* Re: [edk2-devel] ExtScsiPassThru support for Logical SCSI
> devices
>
>
>
> Hi All,
>
>
>
> *Can somebody, comment on this.?*
>
>
>
> Have anyone tried supporting *ExtScsiPassThru* for both Logical and
> Physical devices ??
>
>
>
> *To avoid 2 instances and creation of 2 device paths here, my proposal is*
>
> *1. To filter the Logical and Physical devices, we can add a parameter in
> GetNextTartget() function to inform RAID Driver which type of targets the
> user is looking for. (Physical or Logical).*
>
> *2. To know what type of device connected at that particular Target and
> LUN combination, we can add one more service like.. GetDeviceType() to
> inform the top level user (like UEFI applications/other drivers), to which
> device he is sending a command.*
>
>
>
> I feel this proposal works well and clear, Please let me know if i am
> missing anything here.
>
>
>
> Thanks,
>
> Ravi Kumar
>
>
>
>
>
> On Fri, Jun 14, 2019 at 11:21 AM Wu, Hao A <hao.a.wu at intel.com> wrote:
>
> Hello Ravi Kumar,
>
> *From:* devel at edk2.groups.io [mailto:devel at edk2.groups.io] *On Behalf Of *Ravi
> Kumar Siadri
> *Sent:* Thursday, June 13, 2019 4:18 PM
> *To:* Wu, Hao A
> *Cc:* devel at edk2.groups.io
> *Subject:* Re: [edk2-devel] ExtScsiPassThru support for Logical SCSI
> devices
>
>
>
> Hi Wu Hao A,
>
>
>
> Thanks for the response.
>
> I have added my comments in line.
>
>
>
> Thanks,
>
> Ravi Kumar
>
>
>
>
>
>
>
>
>
> On Wed, Jun 12, 2019 at 1:26 PM Wu, Hao A <hao.a.wu at intel.com> wrote:
>
> Hello Ravi Kumar,
>
>
>
> Inline comments below:
>
>
>
> *From:* devel at edk2.groups.io [mailto:devel at edk2.groups.io] *On Behalf Of *Ravi
> Kumar Siadri
> *Sent:* Wednesday, June 12, 2019 12:01 PM
> *To:* devel at edk2.groups.io
> *Subject:* Re: [edk2-devel] ExtScsiPassThru support for Logical SCSI
> devices
>
>
>
> Hi,
>
>
>
> Can someone help me in clarifying my queries ??
>
>
>
> Thanks,
>
> Ravi Kumar
>
>
>
> On Mon, Jun 10, 2019 at 3:55 PM Ravi Kumar Siadri <
> siadriravikumaruefi at gmail.com> wrote:
>
> Hi all,
>
>
>
> I have couple of queries regarding the
> *EFI_EXT_SCSI_PASS_THRU_ATTRIBUTES_LOGICAL* attribute support in
> *EFI_EXT_SCSI_PASS_THRU_PROTOCOL*.
>
>
>
> *1. *
>
> *The Attributes field of the EFI_EXT_SCSI_PASS_THRU_PROTOCOL interface
> tells if the interface is for physical SCSI devices or logical SCSI
> devices. Drivers for non-RAID SCSI controllers will set both the
> EFI_EXT_SCSI_PASS_THRU_ATTRIBUTES_PHYSICAL, and the
> EFI_EXT_SCSI_PASS_THRU_ATTRIBUTES_LOGICAL bits.*
>
>
>
> If the Drivers is for non-RAID SCSI controllers why to set the
> EFI_EXT_SCSI_PASS_THRU_ATTRIBUTES_LOGICAL bit. Will there be any case that
> non-RAID SCSI controllers have Logical devices connected to it ??
>
>
>
> Per my understanding, every partition on a physical HW device will be
> treated
>
> as a logical device by the firmware.
>
>
>
> So for non-RAID case, both bits will be set for the PassThru protocol
> produced
>
> for the physical device.
>
>
>
> Ravi:
>
> As far as i know RAID controller will treat a partition/drive as logical
> device only if has RIS (raid information sector) information in it.  So i
> don't think partition is treated as logical device.
>
>
>
> Agree.
>
> Then for the non-RAID case, the hardware is considered as a physical
> device and a logical one at the same time.
>
> Since media access protocols like the BlockIO protocol will be produced
> upon the logical instance of the PassThru protocol, it is the reason that
> both bits are set for this case.
>
> (Refer to function DetermineInstallBlockIo() at MdeModulePkg\Bus\Scsi\
> ScsiDiskDxe\ScsiDisk.c)
>
>
>
> *2. *
>
> *Drivers for RAID controllers that allow access to the physical devices
> and logical devices will produce two EFI_EXT_SCSI_PASS_THRU_PROTOCOL
> interfaces:  *
>
> *One with the just the EFI_EXT_SCSI_PASS_THRU_ATTRIBUTES_PHYSICAL bit set
> and another with just the EFI_EXT_SCSI_PASS_THRU_ATTRIBUTES_LOGICAL bit
> set. One interface can be used to access the physical devices attached to
> the RAID controller, and the other can be used to access the logical
> devices attached to the RAID controller for its current configuration.*
>
>
>
> Any background why EFI_EXT_SCSI_PASS_THRU_PROTOCOL needed 2 instances ?
> why can't we install attributes EFI_EXT_SCSI_PASS_THRU_ATTRIBUTES_LOGICAL
> and EFI_EXT_SCSI_PASS_THRU_ATTRIBUTES_PHYSICAL on same Instance ??
>
> How User locates the Instance with
> EFI_EXT_SCSI_PASS_THRU_ATTRIBUTES_LOGICAL bit set and Instance with
> EFI_EXT_SCSI_PASS_THRU_ATTRIBUTES_PHYSICAL bit set. ??
>
>
>
> UEFI spec allows RAID drivers to only produce one PassThru protocol
> interface
>
> with just the XXX_PASS_THRU_LOGICAL bit set when the RAID controller
> select to
>
> not allow direct access to the underlying physical devices.
>
>
>
>           Ravi:
>
> If the RAID Driver supports only Logical or Physical Devices then it is
> fine creating only 1 instance and not allowing other devices which Bit is
> not set. (either  EFI_EXT_SCSI_PASS_THRU_ATTRIBUTES_LOGICAL or
> EFI_EXT_SCSI_PASS_THRU_ATTRIBUTES_PHYSICAL).
>
> But if the RAID driver supports both the Logical and Physical Devices,
> then we have to need 2 instances as per spec. This is going to be an over
> head, while locating instances by the user who want to send commands to
> Target devices connected to RAID controller.
>
> Since each EFI_EXT_SCSI_PASS_THRU_PROTOCOL instance must have an
> associated device path. Only 1 instance can be installed on that particular
> RAID controller handle since the GUID is same for both the instances.
>
> If our intention is to filter the Logical and Physical devices then, we
> can add a parameter in GetNextTartget() function to inform RAID Driver
> which type of targets the user is looking for. (Physical or Logical).
>
>  Right ??
>
>
>
> My take is that the producer of the physical and logical PassThru protocol
> may not be the same vender (or driver).
>
> The logical instance (which determines the configuration of the RAID)
> might have a common logic that applies to common using cases.
>
> The logical one will be used to produce media access protocols, some
> actual HW may not be accessible (e.g. used for data backup) by this
> PassThru protocol instance.
>
> While the physical one can be used to send commands to the underlying
> device for purpose like health/status check or getting device information.
>
> However, I am not an expect for RAID, hope someone else can help to
> provide comments.
>
>
>
> Thanks,
>
> Ravi Kumar
>
>
>
> 
>
>

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