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 {
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