On 21.05.14 11:33, Alexey Kardashevskiy wrote:
On 05/21/2014 07:13 PM, Alexander Graf wrote:
On 21.05.14 11:11, Michael S. Tsirkin wrote:
On Wed, May 21, 2014 at 11:06:09AM +0200, Alexander Graf wrote:
On 21.05.14 10:52, Alexey Kardashevskiy wrote:
On 05/21/2014 06:40 PM, Alexander Graf wrote:
On 15.05.14 11:59, Alexey Kardashevskiy wrote:
Currently SPAPR PHB keeps track of all allocated MSI/MISX
interrupt as
XICS used to be unable to reuse interrupts which becomes a
problem for
dynamic MSI reconfiguration which is happening on guest driver
reload or
PCI hot (un)plug. Another problem is that PHB has a limit of devices
supporting MSI/MSIX (SPAPR_MSIX_MAX_DEVS=32) and there is no good
reason
for that.
This makes use of new XICS ability to reuse interrupts.
This removes cached MSI configuration from SPAPR PHB so the first
IRQ
number
of a device is stored in MSI/MSIX config space so there is no
need to
store
this anywhere else. From now on, SPAPR PHB only keeps flags telling
what
type
of interrupt for which device it has configured in order to return
error if
(for example) MSIX was enabled and the guest is trying to disable
MSI
which
it has not enabled.
This removes a limit for the maximum number of MSIX-enabled devices
per PHB,
now XICS and PCI bus capacity are the only limitation.
This changes migration stream as it fixes
vmstate_spapr_pci_msi::name
which was
wrong since the beginning.
This fixed traces to be more informative.
Signed-off-by: Alexey Kardashevskiy <address@hidden>
---
In reality either MSIX or MSI is enabled, never both. So I could
remove
msi/msix
bitmaps from this patch, would it make sense?
Is this a hard requirement? Does a device have to choose between
MSIX and
MSI or could it theoretically have both enabled? Is this a PCI
limitation,
a PAPR/XICS limitation or just a limitation of your implementation?
My implementation does not have this limitation, I asked if I can
simplify
code by introducing one :)
I cannot see any reason why PCI cannot have both MSI and MSIX enabled
but
it does not seem to be used by anyone => cannot debug and confirm.
PAPR spec assumes that if the guest tries enabling MSIX when MSI is
already
enabled, this is a "change", not enabling both types. But it also
says MSI
and MSIX vector numbers are not shared. Hm.
Yeah, I'm not aware of any limitation on hardware here and I'd
rather not impose one.
Michael, do you know of any hardware that uses MSI *and* MSI-X at
the same time?
Alex
No, and the PCI spec says:
A function is permitted to implement both MSI and MSI-X, but
system
software is
prohibited from enabling both at the same time. If system software
enables both at the same time, the result is undefined.
Ah, cool. So yes Alexey, feel free to impose it :).
Heh. This solves just half of the problem - I still have to keep track of
what device got MSI/MSIX configured via that ibm,change-msi interface. I
was hoping I can store such flag somewhere in a device PCI config space
but
MSI/MSIX enable bit is not good as it is not set when those calls are
made.
And I cannot rely on address/data fields much as the guest can change them
(I already use them to store IRQ numbers and btw it is missing checks when
I read them back for disposal, I'll fix in next round).
Or on "enable" event I could put IRQ numbers to .data of MSI config space
and on "disable" check if it is not zero, then configuration took place,
then I can remove my msi[]/msix[] flag arrays. If the guest did any change
to MSI/MSIX config space (it does not on SPAPR except weird selftest
cases), I compare .data with what ICS can possibly have and either reject
"disable" or handle it and if it breaks XICS - that's too bad for the
stupid guest. Would that be acceptable?