Re: [PATCH] OvmfPkg/PvScsiDxe: Refactor setup of rings to separate function

["Liran Alon" <liran.alon@oracle.com>]

On 01/04/2020 1:19, Laszlo Ersek wrote:
> Hi Liran,
>
> On 03/31/20 13:47, Liran Alon wrote:
>> Previous to this change, PvScsiFreeRings() was not undoing all
>> operations that was done by PvScsiInitRings().
>> This is because PvScsiInitRings() was both preparing rings (Allocate
>> memory and map it for device DMA) and setup the rings against device by
>> issueing a device command. While PvScsiFreeRings() only unmaps the rings
>> and free their memory.
>>
>> Driver do not have a functional error as it makes sure to reset device
>> before every call site to PvScsiFreeRings(). However, this is not
>> intuitive.
>>
>> Therefore, prefer to refactor the setup of the ring against device to a
>> separate function than PvScsiInitRings().
>>
>> Signed-off-by: Liran Alon <liran.alon@oracle.com>
>> ---
>>   OvmfPkg/PvScsiDxe/PvScsi.c | 150 +++++++++++++++++++------------------
>>   1 file changed, 76 insertions(+), 74 deletions(-)
> Thanks for the patch.
>
> I didn't expect this approach -- hoisting the rings exposure from
> SetupRings to Init --, but it turns out that I like it more than my own
> previous suggestion -- pushing ResetAdapter into FreeRings :)
Yeah I thought about it later and liked it to. Hoped you will think the 
same ;)
>
> May I just trouble you with one further request?
>
>> diff --git a/OvmfPkg/PvScsiDxe/PvScsi.c b/OvmfPkg/PvScsiDxe/PvScsi.c
>> index 1ca50390c0e5..5b7fdcbda10b 100644
>> --- a/OvmfPkg/PvScsiDxe/PvScsi.c
>> +++ b/OvmfPkg/PvScsiDxe/PvScsi.c
>> @@ -991,13 +991,6 @@ PvScsiInitRings (
>>     )
>>   {
>>     EFI_STATUS Status;
>> -  union {
>> -    PVSCSI_CMD_DESC_SETUP_RINGS Cmd;
>> -    UINT32                      Uint32;
>> -  } AlignedCmd;
>> -  PVSCSI_CMD_DESC_SETUP_RINGS *Cmd;
>> -
>> -  Cmd = &AlignedCmd.Cmd;
>>   
>>     Status = PvScsiAllocateSharedPages (
>>                Dev,
>> @@ -1032,6 +1025,69 @@ PvScsiInitRings (
>>     }
>>     ZeroMem (Dev->RingDesc.RingCmps, EFI_PAGE_SIZE);
>>   
>> +  return EFI_SUCCESS;
>> +
>> +FreeRingReqs:
>> +  PvScsiFreeSharedPages (
>> +    Dev,
>> +    1,
>> +    Dev->RingDesc.RingReqs,
>> +    &Dev->RingDesc.RingReqsDmaDesc
>> +    );
>> +
>> +FreeRingState:
>> +  PvScsiFreeSharedPages (
>> +    Dev,
>> +    1,
>> +    Dev->RingDesc.RingState,
>> +    &Dev->RingDesc.RingStateDmaDesc
>> +    );
>> +
>> +  return Status;
>> +}
>> +
>> +STATIC
>> +VOID
>> +PvScsiFreeRings (
>> +  IN OUT PVSCSI_DEV *Dev
>> +  )
>> +{
>> +  PvScsiFreeSharedPages (
>> +    Dev,
>> +    1,
>> +    Dev->RingDesc.RingCmps,
>> +    &Dev->RingDesc.RingCmpsDmaDesc
>> +    );
>> +
>> +  PvScsiFreeSharedPages (
>> +    Dev,
>> +    1,
>> +    Dev->RingDesc.RingReqs,
>> +    &Dev->RingDesc.RingReqsDmaDesc
>> +    );
>> +
>> +  PvScsiFreeSharedPages (
>> +    Dev,
>> +    1,
>> +    Dev->RingDesc.RingState,
>> +    &Dev->RingDesc.RingStateDmaDesc
>> +    );
>> +}
>> +
>> +STATIC
>> +EFI_STATUS
>> +PvScsiSetupRings (
>> +  IN OUT PVSCSI_DEV *Dev
>> +  )
>> +{
>> +  union {
>> +    PVSCSI_CMD_DESC_SETUP_RINGS Cmd;
>> +    UINT32                      Uint32;
>> +  } AlignedCmd;
>> +  PVSCSI_CMD_DESC_SETUP_RINGS *Cmd;
>> +
>> +  Cmd = &AlignedCmd.Cmd;
>> +
>>     ZeroMem (Cmd, sizeof (*Cmd));
>>     Cmd->ReqRingNumPages = 1;
>>     Cmd->CmpRingNumPages = 1;
>> @@ -1052,71 +1108,12 @@ PvScsiInitRings (
>>       sizeof (*Cmd) % sizeof (UINT32) == 0,
>>       "Cmd must be multiple of 32-bit words"
>>       );
>> -  Status = PvScsiWriteCmdDesc (
>> -             Dev,
>> -             PvScsiCmdSetupRings,
>> -             (UINT32 *)Cmd,
>> -             sizeof (*Cmd) / sizeof (UINT32)
>> -             );
>> -  if (EFI_ERROR (Status)) {
>> -    goto FreeRingCmps;
>> -  }
>> -
>> -  return EFI_SUCCESS;
>> -
>> -FreeRingCmps:
>> -  PvScsiFreeSharedPages (
>> -    Dev,
>> -    1,
>> -    Dev->RingDesc.RingCmps,
>> -    &Dev->RingDesc.RingCmpsDmaDesc
>> -    );
>> -
>> -FreeRingReqs:
>> -  PvScsiFreeSharedPages (
>> -    Dev,
>> -    1,
>> -    Dev->RingDesc.RingReqs,
>> -    &Dev->RingDesc.RingReqsDmaDesc
>> -    );
>> -
>> -FreeRingState:
>> -  PvScsiFreeSharedPages (
>> -    Dev,
>> -    1,
>> -    Dev->RingDesc.RingState,
>> -    &Dev->RingDesc.RingStateDmaDesc
>> -    );
>> -
>> -  return Status;
>> -}
>> -
>> -STATIC
>> -VOID
>> -PvScsiFreeRings (
>> -  IN OUT PVSCSI_DEV *Dev
>> -  )
>> -{
>> -  PvScsiFreeSharedPages (
>> -    Dev,
>> -    1,
>> -    Dev->RingDesc.RingCmps,
>> -    &Dev->RingDesc.RingCmpsDmaDesc
>> -    );
>> -
>> -  PvScsiFreeSharedPages (
>> -    Dev,
>> -    1,
>> -    Dev->RingDesc.RingReqs,
>> -    &Dev->RingDesc.RingReqsDmaDesc
>> -    );
>> -
>> -  PvScsiFreeSharedPages (
>> -    Dev,
>> -    1,
>> -    Dev->RingDesc.RingState,
>> -    &Dev->RingDesc.RingStateDmaDesc
>> -    );
>> +  return PvScsiWriteCmdDesc (
>> +           Dev,
>> +           PvScsiCmdSetupRings,
>> +           (UINT32 *)Cmd,
>> +           sizeof (*Cmd) / sizeof (UINT32)
>> +           );
>>   }
>>   
>>   STATIC
>> @@ -1157,6 +1154,10 @@ PvScsiInit (
>>     if (EFI_ERROR (Status)) {
>>       goto RestorePciAttributes;
>>     }
>> +  Status = PvScsiSetupRings (Dev);
>> +  if (EFI_ERROR (Status)) {
>> +    goto FreeRings;
>> +  }
> If you could move the PvScsiSetupRings() call *below* the DMA buffer
> allocation (and rework the error path accordingly -- basically replacing
> the "UnsetupRings" action with a "FreeDmaBuffer" action), then this
> patch would be *perfect*.
>
> Because then, the PvScsiUninit() order of actions would be a 100% mirror
> for PvScsiInit()'s; namely with PvScsiResetAdapter() at the top of
> PvScsiUninit() perfectly matching PvScsiSetupRings() at the end of
> PvScsiInit()!
>
> I don't want to annoy you too much, so if you really want to stick with
> this version, I'll take it as well.

Good suggestion. Let me submit a v2 of this patch.

-Liran

>
> Thanks!
> Laszlo
>
>>   
>>     //
>>     // Allocate DMA communication buffer
>> @@ -1168,7 +1169,7 @@ PvScsiInit (
>>                &Dev->DmaBufDmaDesc
>>                );
>>     if (EFI_ERROR (Status)) {
>> -    goto FreeRings;
>> +    goto UnsetupRings;
>>     }
>>   
>>     //
>> @@ -1202,13 +1203,14 @@ PvScsiInit (
>>   
>>     return EFI_SUCCESS;
>>   
>> -FreeRings:
>> +UnsetupRings:
>>     //
>>     // Reset device to stop device usage of the rings.
>>     // This is required to safely free the rings.
>>     //
>>     PvScsiResetAdapter (Dev);
>>   
>> +FreeRings:
>>     PvScsiFreeRings (Dev);
>>   
>>   RestorePciAttributes:
>>