On 03/07/18 17:21, Hook, Gary wrote: > On 7/3/2018 10:55 AM, Joe Perches wrote: >> On Tue, 2018-07-03 at 07:56 -0500, Gary R Hook wrote: >>> On 07/03/2018 05:07 AM, Joe Perches wrote: >>>> On Tue, 2018-07-03 at 07:40 +0100, Colin King wrote: >>>>> Currently tag is being assigned but not used, it is missing from >>>>> the dev_err message, so add it in. >>>>> >>>>> Cleans up clang warning: >>>>> warning: variable 'tag' set but not used [-Wunused-but-set-variable] >>>> >>>> [] >>>>> diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c >>>> >>>> [] >>>>> @@ -616,9 +616,9 @@ static void iommu_print_event(struct amd_iommu >>>>> *iommu, void *__evt) >>>>> pasid = ((event[0] >> 16) & 0xFFFF) >>>>> | ((event[1] << 6) & 0xF0000); >>>>> tag = event[1] & 0x03FF; >>>>> - dev_err(dev, "INVALID_PPR_REQUEST device=%02x:%02x.%x >>>>> pasid=0x%05x address=0x%016llx flags=0x%04x]\n", >>>>> + dev_err(dev, "INVALID_PPR_REQUEST device=%02x:%02x.%x >>>>> pasid=0x%05x address=0x%016llx flags=0x%04x tag=0x%03x]\n", >>>>> PCI_BUS_NUM(devid), PCI_SLOT(devid), PCI_FUNC(devid), >>>>> - pasid, address, flags); >>>>> + pasid, address, flags, tag); >>>> >>>> Seems to have a superfluous ] that should be removed. >>> >>> Yeah, I pretty much messed up all of the log messages in that function. >>> My apologies. I'll create a patch for that problem; it shouldn't be >>> fixed here. > > Well, no, I misremembered. The extraneous square brace has been there > forever. Needs fixin', though. > The opening square bracket is much earlier: dev_err(dev, "AMD-Vi: Event logged ["); ..and all the subsequent dev_err messages have the trailing square bracket. > >> I also wonder why event is declared volatile and then >> dereferenced with [<constant>] multiple times. >> >> Maybe each array dereference should be stored as a >> local variable instead. > > (I know you know this, but as I understand it) Event is pointing into > the (hardware's) event buffer, and the data structure has the potential > of changing out from under us if the device does something without our > knowledge. Since volatile hints to the compiler of this possibility, I > believe the compiler should manage this situation. But I could be wrong. > > I don't know that we need to atomically copy all 16 bytes into a local > buffer, as I don't think it's possible for the device to step on itself. > It will just stop recording events if the buffer gets full. At this > moment I think volatile is overkill, at least for the EPYC/Ryzen IOMMU. -- To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
