The LBA Format Data structure is dword-sized, but struct nvme_lba_format erroneously contains an additional member, misaligning all LBAF descriptors after the first and causing them to be misinterpreted. Remove it.
Signed-off-by: Florian Larysch fl@n621.de --- src/hw/nvme-int.h | 1 - 1 file changed, 1 deletion(-)
diff --git a/src/hw/nvme-int.h b/src/hw/nvme-int.h index a4c1555..5779203 100644 --- a/src/hw/nvme-int.h +++ b/src/hw/nvme-int.h @@ -156,7 +156,6 @@ struct nvme_lba_format { u16 ms; u8 lbads; u8 rp; - u8 res; };
struct nvme_identify_ns {
On Sun, Jan 23, 2022 at 05:43:57PM +0100, Florian Larysch wrote:
The LBA Format Data structure is dword-sized, but struct nvme_lba_format erroneously contains an additional member, misaligning all LBAF descriptors after the first and causing them to be misinterpreted. Remove it.
Thanks. I don't know enough about NVMe to review this patch though. Maybe Julian or Alex could comment?
-Kevin
Signed-off-by: Florian Larysch fl@n621.de
src/hw/nvme-int.h | 1 - 1 file changed, 1 deletion(-)
diff --git a/src/hw/nvme-int.h b/src/hw/nvme-int.h index a4c1555..5779203 100644 --- a/src/hw/nvme-int.h +++ b/src/hw/nvme-int.h @@ -156,7 +156,6 @@ struct nvme_lba_format { u16 ms; u8 lbads; u8 rp;
- u8 res;
};
struct nvme_identify_ns {
2.34.1
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On Thu, Jan 27, 2022 at 11:37:52AM -0500, Kevin O'Connor wrote:
Thanks. I don't know enough about NVMe to review this patch though. Maybe Julian or Alex could comment?
Happy to hear their comments on this. However, I can also try to explain the reasoning in a bit more detail.
This follows from the NVMe spec[1]: The Identify command returns a data structure that contains packed LBAF records (Figure 249, starting at offset 131). This is represented by struct nvme_identify_ns in the SeaBIOS code.
Figure 250 gives the structure of these records and this is where the aforementioned discrepancy lies.
I think what happened was that somebody mistook the reserved 6 uppermost bits as a whole byte and put it into struct nvme_lba_format as such. To correctly parse the RP field, you'd still need to mask off these bits, but the code only uses the LBADS/MS fields anyway.
I encountered this on an NVMe device that had FLBAS[3:0] != 0, which caused nonsensical outputs of the various dprintf()s and also throws off everything that depends on knowing the block size. Empirically, the patch fixes these problems.
[1] https://nvmexpress.org/wp-content/uploads/NVM-Express-1_4c-2021.06.28-Ratifi...
On Tue, Feb 01, 2022 at 08:39:10PM +0100, Florian Larysch wrote:
On Thu, Jan 27, 2022 at 11:37:52AM -0500, Kevin O'Connor wrote:
Thanks. I don't know enough about NVMe to review this patch though. Maybe Julian or Alex could comment?
Happy to hear their comments on this. However, I can also try to explain the reasoning in a bit more detail.
This follows from the NVMe spec[1]: The Identify command returns a data structure that contains packed LBAF records (Figure 249, starting at offset 131). This is represented by struct nvme_identify_ns in the SeaBIOS code.
Figure 250 gives the structure of these records and this is where the aforementioned discrepancy lies.
Thanks. I agree that this should be fixed in SeaBIOS.
However, your patch removes the "reserved" field, which doesn't look correct. It sounds like the "res" struct member should remain, but the "lbads" and "rp" members should be turned into a new "lbads_rp" member. Also, the nvme.c code should be updated so that the read of lbads performs the proper bit masking.
-Kevin
I think what happened was that somebody mistook the reserved 6 uppermost bits as a whole byte and put it into struct nvme_lba_format as such. To correctly parse the RP field, you'd still need to mask off these bits, but the code only uses the LBADS/MS fields anyway.
I encountered this on an NVMe device that had FLBAS[3:0] != 0, which caused nonsensical outputs of the various dprintf()s and also throws off everything that depends on knowing the block size. Empirically, the patch fixes these problems.
[1] https://nvmexpress.org/wp-content/uploads/NVM-Express-1_4c-2021.06.28-Ratifi...
On 02.02.22 02:52, Kevin O'Connor wrote:
On Tue, Feb 01, 2022 at 08:39:10PM +0100, Florian Larysch wrote:
On Thu, Jan 27, 2022 at 11:37:52AM -0500, Kevin O'Connor wrote:
Thanks. I don't know enough about NVMe to review this patch though. Maybe Julian or Alex could comment?
Happy to hear their comments on this. However, I can also try to explain the reasoning in a bit more detail.
This follows from the NVMe spec[1]: The Identify command returns a data structure that contains packed LBAF records (Figure 249, starting at offset 131). This is represented by struct nvme_identify_ns in the SeaBIOS code.
Figure 250 gives the structure of these records and this is where the aforementioned discrepancy lies.
Thanks. I agree that this should be fixed in SeaBIOS.
However, your patch removes the "reserved" field, which doesn't look correct. It sounds like the "res" struct member should remain, but the "lbads" and "rp" members should be turned into a new "lbads_rp" member. Also, the nvme.c code should be updated so that the read of lbads performs the proper bit masking.
Looking at the spec, lbads is a full well aligned 8 bits. The collision here is between rp and res, with rp taking only 2 bits and res the remaining 6. Is using bitfields acceptable in SeaBIOS? If so, the patch below should automatically give us masking as well.
Alex
diff --git a/src/hw/nvme-int.h b/src/hw/nvme-int.h index f9c807e..9b3015b 100644 --- a/src/hw/nvme-int.h +++ b/src/hw/nvme-int.h @@ -145,8 +145,8 @@ struct nvme_identify_ns_list { struct nvme_lba_format { u16 ms; u8 lbads; - u8 rp; - u8 res; + u8 rp : 2; + u8 res : 6; };
struct nvme_identify_ns {
Amazon Development Center Germany GmbH Krausenstr. 38 10117 Berlin Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B Sitz: Berlin Ust-ID: DE 289 237 879
On Wed, Feb 02, 2022 at 11:50:50AM +0100, Alexander Graf wrote:
On 02.02.22 02:52, Kevin O'Connor wrote:
On Tue, Feb 01, 2022 at 08:39:10PM +0100, Florian Larysch wrote:
On Thu, Jan 27, 2022 at 11:37:52AM -0500, Kevin O'Connor wrote:
Thanks. I don't know enough about NVMe to review this patch though. Maybe Julian or Alex could comment?
Happy to hear their comments on this. However, I can also try to explain the reasoning in a bit more detail.
This follows from the NVMe spec[1]: The Identify command returns a data structure that contains packed LBAF records (Figure 249, starting at offset 131). This is represented by struct nvme_identify_ns in the SeaBIOS code.
Figure 250 gives the structure of these records and this is where the aforementioned discrepancy lies.
Thanks. I agree that this should be fixed in SeaBIOS.
However, your patch removes the "reserved" field, which doesn't look correct. It sounds like the "res" struct member should remain, but the "lbads" and "rp" members should be turned into a new "lbads_rp" member. Also, the nvme.c code should be updated so that the read of lbads performs the proper bit masking.
Looking at the spec, lbads is a full well aligned 8 bits. The collision here is between rp and res, with rp taking only 2 bits and res the remaining 6.
Ah, I misread the spec. So, the original patch removing the "res" struct member should be fine.
Is using bitfields acceptable in SeaBIOS? If so, the patch below should automatically give us masking as well.
I'd recommend against using C bitfields to access hardware registers.
-Kevin
On 02.02.22 16:24, Kevin O'Connor wrote:
On Wed, Feb 02, 2022 at 11:50:50AM +0100, Alexander Graf wrote:
On 02.02.22 02:52, Kevin O'Connor wrote:
On Tue, Feb 01, 2022 at 08:39:10PM +0100, Florian Larysch wrote:
On Thu, Jan 27, 2022 at 11:37:52AM -0500, Kevin O'Connor wrote:
Thanks. I don't know enough about NVMe to review this patch though. Maybe Julian or Alex could comment?
Happy to hear their comments on this. However, I can also try to explain the reasoning in a bit more detail.
This follows from the NVMe spec[1]: The Identify command returns a data structure that contains packed LBAF records (Figure 249, starting at offset 131). This is represented by struct nvme_identify_ns in the SeaBIOS code.
Figure 250 gives the structure of these records and this is where the aforementioned discrepancy lies.
Thanks. I agree that this should be fixed in SeaBIOS.
However, your patch removes the "reserved" field, which doesn't look correct. It sounds like the "res" struct member should remain, but the "lbads" and "rp" members should be turned into a new "lbads_rp" member. Also, the nvme.c code should be updated so that the read of lbads performs the proper bit masking.
Looking at the spec, lbads is a full well aligned 8 bits. The collision here is between rp and res, with rp taking only 2 bits and res the remaining 6.
Ah, I misread the spec. So, the original patch removing the "res" struct member should be fine.
Yes, the original patch works too. There is currently no user of the rp field, so nothing to mask against.
Is using bitfields acceptable in SeaBIOS? If so, the patch below should automatically give us masking as well.
I'd recommend against using C bitfields to access hardware registers.
This is an in-RAM data structure. But in any case, let's just go with the original patch.
Reviewed-by: Alexander Graf graf@amazon.com
Alex
Amazon Development Center Germany GmbH Krausenstr. 38 10117 Berlin Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B Sitz: Berlin Ust-ID: DE 289 237 879
On Sun, Jan 23, 2022 at 05:43:57PM +0100, Florian Larysch wrote:
The LBA Format Data structure is dword-sized, but struct nvme_lba_format erroneously contains an additional member, misaligning all LBAF descriptors after the first and causing them to be misinterpreted. Remove it.
Thanks. I committed this change.
-Kevin
-
Alexander Graf -
Florian Larysch -
Kevin O'Connor