On Wed, Jun 01, 2022 at 07:56:47PM +0200, Lukas Wunner wrote: > On Wed, Jun 01, 2022 at 10:16:15AM -0700, Ira Weiny wrote: > > On Wed, Jun 01, 2022 at 09:18:08AM +0200, Lukas Wunner wrote: > > > You only need to re-check the Data Object Ready bit on the last-but-one > > > dword in case the function was reset concurrently. Per sec. 6.30.2, > > > "An FLR to a Function must result in the aborting of any DOE transfer > > > in progress." > > > > I think I disagree. Even if we do that and an FLR comes before the last read > > the last read could be 0's. > > PCIe r6.0, Table 7-316 says: > > "If there is no additional data object ready for transfer, the > DOE instance must clear this bit after the entire data object has been > transferred, as indicated by software writing to the DOE Read Data > Mailbox Register after reading the final DW of the data object." > > Remember that you *read* a dword from the mailbox and then acknowledge > reception to the mailbox by *writing* a dword to the mailbox. > > So you check that the Data Object Ready bit is set before acknowledging > the final dword with a register write. That's race-free. Ok. > > (I realize me talking about the "last-but-one dword" above was quite > unclear, sorry about that.) > Ah yes. Ok, I'll put in a check before the final write. Ira
