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ivshmem: Propagate errors through ivshmem_recv_setup()

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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>
This commit is contained in:
Markus Armbruster 2016-03-15 19:34:41 +01:00
parent 3a55fc0f24
commit 1309cf448a
3 changed files with 95 additions and 63 deletions
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20
docs/specs/ivshmem-spec.txt
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@ -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,