diff options
| author | Markus Armbruster <armbru@redhat.com> | 2016-03-15 19:34:41 +0100 |
|---|---|---|
| committer | Markus Armbruster <armbru@redhat.com> | 2016-03-21 21:29:01 +0100 |
| commit | 1309cf448a6d88d8a693c15d5b11ad07af2321ab (patch) | |
| tree | 85ff2c7eb4cc4403a8f27478d7d188429e888a07 /docs/specs/ivshmem-spec.txt | |
| parent | 3a55fc0f243104998bee5106b121cff257df5d33 (diff) | |
ivshmem: Propagate errors through ivshmem_recv_setup()
This kills off the funny state described in the previous commit.
Simplify ivshmem_io_read() accordingly, and update documentation.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1458066895-20632-27-git-send-email-armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Diffstat (limited to 'docs/specs/ivshmem-spec.txt')
| -rw-r--r-- | docs/specs/ivshmem-spec.txt | 20 |
1 files changed, 11 insertions, 9 deletions
diff --git a/docs/specs/ivshmem-spec.txt b/docs/specs/ivshmem-spec.txt index 0cd63adff0..4c33973552 100644 --- a/docs/specs/ivshmem-spec.txt +++ b/docs/specs/ivshmem-spec.txt @@ -62,11 +62,11 @@ There are two ways to use this device: likely want to write a kernel driver to handle interrupts. Requires the device to be configured for interrupts, obviously. -If the device is configured for interrupts, BAR2 is initially invalid. -It becomes safely accessible only after the ivshmem server provided -the shared memory. Guest software should wait for the IVPosition -register (described below) to become non-negative before accessing -BAR2. +Before QEMU 2.6.0, BAR2 can initially be invalid if the device is +configured for interrupts. It becomes safely accessible only after +the ivshmem server provided the shared memory. Guest software should +wait for the IVPosition register (described below) to become +non-negative before accessing BAR2. The device is not capable to tell guest software whether it is configured for interrupts. @@ -82,7 +82,7 @@ BAR 0 contains the following registers: 4 4 read/write 0 Interrupt Status bit 0: peer interrupt bit 1..31: reserved - 8 4 read-only 0 or -1 IVPosition + 8 4 read-only 0 or ID IVPosition 12 4 write-only N/A Doorbell bit 0..15: vector bit 16..31: peer ID @@ -100,12 +100,14 @@ when an interrupt request from a peer is received. Reading the register clears it. IVPosition Register: if the device is not configured for interrupts, -this is zero. Else, it's -1 for a short while after reset, then -changes to the device's ID (between 0 and 65535). +this is zero. Else, it is the device's ID (between 0 and 65535). + +Before QEMU 2.6.0, the register may read -1 for a short while after +reset. There is no good way for software to find out whether the device is configured for interrupts. A positive IVPosition means interrupts, -but zero could be either. The initial -1 cannot be reliably observed. +but zero could be either. Doorbell Register: writing this register requests to interrupt a peer. The written value's high 16 bits are the ID of the peer to interrupt, |