From 897efb977ffb23405e15e31533d5487b13873f00 Mon Sep 17 00:00:00 2001 From: Laszlo Ersek Date: Fri, 18 Aug 2017 03:22:06 +0200 Subject: MdeModulePkg/ScsiBusDxe: don't produce ScsiIo for nonexistent LUNs, part 1 The SPC-4 spec says about the INQUIRY data, in "Table 138 -- Peripheral qualifier": > Qualifier = 011b The device server is not capable of supporting a > peripheral device on this logical unit. For this > peripheral qualifier the peripheral device type shall > be set to 1Fh. All other peripheral device type values > are reserved for this peripheral qualifier. Accordingly, the DiscoverScsiDevice() function returns FALSE if Peripheral_Qualifier is 3 decimal, but Peripheral_Type differs from 1Fh. This is a valid sanity check -- such combinations are reserved. When Peripheral_Qualifier is 3, and Peripheral_Type is 1Fh, then DiscoverScsiDevice() returns TRUE. While this combination is not reserved, returning TRUE for it is incorrect: Peripheral_Type 1Fh stands for "Unknown or no device type", and this combination is returned in particular when the INQUIRY command was directed to a nonexistent LUN. Quoting the spec: > In response to an INQUIRY command received by an incorrect logical unit, > the SCSI target device shall return the INQUIRY data with the peripheral > qualifier set to the value defined in 6.4.2. [...] > > [...] > > The PERIPHERAL QUALIFIER field and PERIPHERAL DEVICE TYPE field identify > the peripheral device connected to the logical unit. If the SCSI target > device is not capable of supporting a peripheral device connected to > this logical unit, the device server shall set these fields to 7Fh > (i.e., PERIPHERAL QUALIFIER field set to 011b and PERIPHERAL DEVICE TYPE > field set to 1Fh). The consequence of this bug is that for each nonexistent Target/LUN pair, we produce a useless ScsiIo protocol interface. The internal "ScsiIoDevice->ScsiDeviceType" field will be set to 0x1f, and it will be returned to higher-level SCSI drivers when they call ScsiIo->GetDeviceType(). Given that 0x1f means "Unknown or no device type", no higher-level driver can ever support it, so these ScsiIo protocol interfaces are useless. The fix is to return FALSE for the (Peripheral_Qualifier=3, Peripheral_Type=0x1f) combination. With that however we reject the whole Peripheral_Qualifier=3 space (justifiedly -- see the definition above), which lets us simplify the code. Cc: Eric Dong Cc: Feng Tian Cc: Hannes Reinecke Cc: Paolo Bonzini Cc: Star Zeng Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Laszlo Ersek Reviewed-by: Star Zeng --- MdeModulePkg/Bus/Scsi/ScsiBusDxe/ScsiBus.c | 10 +--------- 1 file changed, 1 insertion(+), 9 deletions(-) (limited to 'MdeModulePkg/Bus/Scsi') diff --git a/MdeModulePkg/Bus/Scsi/ScsiBusDxe/ScsiBus.c b/MdeModulePkg/Bus/Scsi/ScsiBusDxe/ScsiBus.c index 0802b61..72e3da8 100644 --- a/MdeModulePkg/Bus/Scsi/ScsiBusDxe/ScsiBus.c +++ b/MdeModulePkg/Bus/Scsi/ScsiBusDxe/ScsiBus.c @@ -1349,19 +1349,11 @@ DiscoverScsiDevice ( // // Retrieved inquiry data successfully // - if ((InquiryData->Peripheral_Qualifier != 0) && - (InquiryData->Peripheral_Qualifier != 3)) { + if (InquiryData->Peripheral_Qualifier != 0) { ScsiDeviceFound = FALSE; goto Done; } - if (InquiryData->Peripheral_Qualifier == 3) { - if (InquiryData->Peripheral_Type != 0x1f) { - ScsiDeviceFound = FALSE; - goto Done; - } - } - if (0x1e >= InquiryData->Peripheral_Type && InquiryData->Peripheral_Type >= 0xa) { ScsiDeviceFound = FALSE; goto Done; -- cgit v1.1