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Subject: Re: [virtio-dev] [PATCH v2] Add lifetime metrics to virtio-blk
On Thu, Feb 25, 2021 at 04:41:41PM -0700, Enrico Granata wrote: > @@ -4611,6 +4615,7 @@ \subsection{Device Operation}\label{sec:Device > Types / Block Device / Device Ope > #define VIRTIO_BLK_T_GET_ID 8 > #define VIRTIO_BLK_T_DISCARD 11 > #define VIRTIO_BLK_T_WRITE_ZEROES 13 > +#define VIRTIO_BLK_T_GET_LIFETIME 15 Sorry I missed this in the previous revision: There is some funny business in the Linux drivers/block/virtio_blk.c driver and QEMU hw/block/virtio-blk.c device implementations where the least significant bit indicates a driver-to-device DMA transfer when set and a device-to-driver DMA transfer when clear. That's why DISCARD/WRITE_ZEROES have odd-numbered request types but GET_ID has an even-numbered request type. The implementations should probably be overhauled to stop doing this. There doesn't seem to be a good reason for it! :P To make life easy, please choose an even-numbered request type. That way these implementations will treat VIRTIO_BLK_T_GET_LIFETIME as a "read" instead of a "write". 10, 12, or 14 would work. Otherwise: Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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