It is currently not possible to run a pseries-2.12 or older machine
with HV KVM. QEMU prints the following and exits right away.
qemu-system-ppc64: KVM doesn't support for base page shift 34
The "hpt-max-page-size" capability was recently added to spapr to hide
host configuration details from HPT mode guests. Its default value for
newer machine types is 64k.
For backwards compatibility, pseries-2.12 and older machine types need
a different value. This is handled as usual in a class init function.
The default value is 16G, ie, all page sizes supported by POWER7 and
newer CPUs, but HV KVM requires guest pages to be hpa contiguous as
well as gpa contiguous. The default value is the page size used to
back the guest RAM in this case.
Unfortunately kvmppc_hpt_needs_host_contiguous_pages()->kvm_enabled() is
called way before KVM init and returns false, even if the user requested
KVM. We thus end up selecting 16G, which isn't supported by HV KVM. The
default value must be set during machine init, because we can safely
assume that KVM is initialized at this point.
We fix this by moving the logic to default_caps_with_cpu(). Since the
user cannot pass cap-hpt-max-page-size=0, we set the default to 0 in
the pseries-2.12 class init function and use that as a flag to do the
real work.
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
KVM HV has some limitations (deriving from the hardware) that mean not all
host-cpu supported pagesizes may be usable in the guest. At present this
means that KVM guests and TCG guests may see different available page sizes
even if they notionally have the same vcpu model. This is confusing and
also prevents migration between TCG and KVM.
This patch makes the environment consistent by always allowing the same set
of pagesizes. Since we can't remove the KVM limitations, we do this by
always applying the same limitations it has, even to TCG guests.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Greg Kurz <groug@kaod.org>
The way we used to handle KVM allowable guest pagesizes for PAPR guests
required some convoluted checking of memory attached to the guest.
The allowable pagesizes advertised to the guest cpus depended on the memory
which was attached at boot, but then we needed to ensure that any memory
later hotplugged didn't change which pagesizes were allowed.
Now that we have an explicit machine option to control the allowable
maximum pagesize we can simplify this. We just check all memory backends
against that declared pagesize. We check base and cold-plugged memory at
reset time, and hotplugged memory at pre_plug() time.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Greg Kurz <groug@kaod.org>
The way the POWER Hash Page Table (HPT) MMU is virtualized by KVM HV means
that every page that the guest puts in the pagetables must be truly
physically contiguous, not just GPA-contiguous. In effect this means that
an HPT guest can't use any pagesizes greater than the host page size used
to back its memory.
At present we handle this by changing what we advertise to the guest based
on the backing pagesizes. This is pretty bad, because it means the guest
sees a different environment depending on what should be host configuration
details.
As a start on fixing this, we add a new capability parameter to the
pseries machine type which gives the maximum allowed pagesizes for an
HPT guest. For now we just create and validate the parameter without
making it do anything.
For backwards compatibility, on older machine types we set it to the max
available page size for the host. For the 3.0 machine type, we fix it to
16, the intention being to only allow HPT pagesizes up to 64kiB by default
in future.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Greg Kurz <groug@kaod.org>
spapr capabilities have an apply hook to actually activate (or deactivate)
the feature in the system at reset time. However, a number of capabilities
affect the setup of cpus, and need to be applied to each of them -
including hotplugged cpus for extra complication. To make this simpler,
add an optional cpu_apply hook that is called from spapr_cpu_reset().
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Previously, the effective values of the various spapr capability flags
were only determined at machine reset time. That was a lazy way of making
sure it was after cpu initialization so it could use the cpu object to
inform the defaults.
But we've now improved the compat checking code so that we don't need to
instantiate the cpus to use it. That lets us move the resolution of the
capability defaults much earlier.
This is going to be necessary for some future capabilities.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
ppc_check_compat() is used in a number of places to check if a cpu object
supports a certain compatiblity mode, subject to various constraints.
It takes a PowerPCCPU *, however it really only depends on the cpu's class.
We have upcoming cases where it would be useful to make compatibility
checks before we fully instantiate the cpu objects.
ppc_type_check_compat() will now make an equivalent check, but based on a
CPU's QOM typename instead of an instantiated CPU object.
We make use of the new interface in several places in spapr, where we're
essentially making a global check, rather than one specific to a particular
cpu. This avoids some ugly uses of first_cpu to grab a "representative"
instance.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
In default_caps_with_cpu() we set spapr_cap_cfpc to broken for POWER8
processors and before.
Since we no longer require private l1d cache on POWER8 for this cap to
be set to workaround change this to default to broken for POWER7
processors and before.
Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
The sxxm (speculative execution exploit mitigation) machine type is a
variant of the 2.12 machine type with workarounds for speculative
execution vulnerabilities enabled by default.
Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Convert cap-ibs (indirect branch speculation) to a custom spapr-cap
type.
All tristate caps have now been converted to custom spapr-caps, so
remove the remaining support for them.
Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
[dwg: Don't explicitly list "?"/help option, trust convention]
[dwg: Fold tristate removal into here, to not break bisect]
[dwg: Fix minor style problems]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
There are currently 2 implemented types of spapr-caps, boolean and
tristate. However there may be a need for caps which don't fit either of
these options. Add a custom capability type for which a list of custom
valid strings can be specified and implement the get/set functions for
these. Also add a field for help text to describe the available options.
Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
[dwg: Change "help" option to "?" matching qemu conventions]
[dwg: Add ATTRIBUTE_UNUSED to avoid breaking bisect]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
The spapr-cap cap-ibs can only have values broken or fixed as there is
no explicit workaround required. Currently setting the value workaround
for this cap will hit an assert if the guest makes the hcall
h_get_cpu_characteristics.
Report an error when attempting to apply the setting with a more helpful
error message.
Reported-by: Satheesh Rajendran <sathnaga@linux.vnet.ibm.com>
Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Change the macro that generates the vmstate migration field and the needed
function for the spapr-caps to take the full spapr-cap name. This has
the benefit of meaning this instance will be picked up when greping
for the spapr-caps and making it more obvious what this macro is doing.
Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Add new tristate cap cap-ibs to represent the indirect branch
serialisation capability.
Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Add new tristate cap cap-sbbc to represent the speculation barrier
bounds checking capability.
Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Add new tristate cap cap-cfpc to represent the cache flush on privilege
change capability.
Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
spapr_caps are used to represent the level of support for various
capabilities related to the spapr machine type. Currently there is
only support for boolean capabilities.
Add support for tristate capabilities by implementing their get/set
functions. These capabilities can have the values 0, 1 or 2
corresponding to broken, workaround and fixed.
Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
The vmstate description and the contained needed function for migration
of spapr_caps is the same for each cap, with the name of the cap
substituted. As such introduce a macro to allow for easier generation of
these.
Convert the three existing spapr_caps (htm, vsx, and dfp) to use this
macro.
Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
The options field here is intended to list the available values for the
capability. It's not used yet, because the existing capabilities are
boolean.
We're going to add capabilities that aren't, but in that case the info on
the possible values can be folded into the .description field.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Currently spapr_caps are tied to boolean values (on or off). This patch
reworks the caps so that they can have any uint8 value. This allows more
capabilities with various values to be represented in the same way
internally. Capabilities are numbered in ascending order. The internal
representation of capability values is an array of uint8s in the
sPAPRMachineState, indexed by capability number.
Capabilities can have their own name, description, options, getter and
setter functions, type and allow functions. They also each have their own
section in the migration stream. Capabilities are only migrated if they
were explictly set on the command line, with the assumption that
otherwise the default will match.
On migration we ensure that the capability value on the destination
is greater than or equal to the capability value from the source. So
long at this remains the case then the migration is considered
compatible and allowed to continue.
This patch implements generic getter and setter functions for boolean
capabilities. It also converts the existings cap-htm, cap-vsx and
cap-dfp capabilities to this new format.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Decimal Floating Point has been available on POWER7 and later (server)
cpus. However, it can be disabled on the hypervisor, meaning that it's
not available to guests.
We currently handle this by conditionally advertising DFP support in the
device tree depending on whether the guest CPU model supports it - which
can also depend on what's allowed in the host for -cpu host. That can lead
to confusion on migration, since host properties are silently affecting
guest visible properties.
This patch handles it by treating it as an optional capability for the
pseries machine type.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Greg Kurz <groug@kaod.org>
We currently have some conditionals in the spapr device tree code to decide
whether or not to advertise the availability of the VMX (aka Altivec) and
VSX vector extensions to the guest, based on whether the guest cpu has
those features.
This can lead to confusion and subtle failures on migration, since it makes
a guest visible change based only on host capabilities. We now have a
better mechanism for this, in spapr capabilities flags, which explicitly
depend on user options rather than host capabilities.
Rework the advertisement of VSX and VMX based on a new VSX capability. We
no longer bother with a conditional for VMX support, because every CPU
that's ever been supported by the pseries machine type supports VMX.
NOTE: Some userspace distributions (e.g. RHEL7.4) already rely on
availability of VSX in libc, so using cap-vsx=off may lead to a fatal
SIGILL in init.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Greg Kurz <groug@kaod.org>
Now that the "pseries" machine type implements optional capabilities (well,
one so far) there's the possibility of having different capabilities
available at either end of a migration. Although arguably a user error,
it would be nice to catch this situation and fail as gracefully as we can.
This adds code to migrate the capabilities flags. These aren't pulled
directly into the destination's configuration since what the user has
specified on the destination command line should take precedence. However,
they are checked against the destination capabilities.
If the source was using a capability which is absent on the destination,
we fail the migration, since that could easily cause a guest crash or other
bad behaviour. If the source lacked a capability which is present on the
destination we warn, but allow the migration to proceed.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Greg Kurz <groug@kaod.org>
This adds an spapr capability bit for Hardware Transactional Memory. It is
enabled by default for pseries-2.11 and earlier machine types. with POWER8
or later CPUs (as it must be, since earlier qemu versions would implicitly
allow it). However it is disabled by default for the latest pseries-2.12
machine type.
This means that with the latest machine type, HTM will not be available,
regardless of CPU, unless it is explicitly enabled on the command line.
That change is made on the basis that:
* This way running with -M pseries,accel=tcg will start with whatever cpu
and will provide the same guest visible model as with accel=kvm.
- More specifically, this means existing make check tests don't have
to be modified to use cap-htm=off in order to run with TCG
* We hope to add a new "HTM without suspend" feature in the not too
distant future which could work on both POWER8 and POWER9 cpus, and
could be enabled by default.
* Best guesses suggest that future POWER cpus may well only support the
HTM-without-suspend model, not the (frankly, horribly overcomplicated)
POWER8 style HTM with suspend.
* Anecdotal evidence suggests problems with HTM being enabled when it
wasn't wanted are more common than being missing when it was.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Greg Kurz <groug@kaod.org>
Because PAPR is a paravirtual environment access to certain CPU (or other)
facilities can be blocked by the hypervisor. PAPR provides ways to
advertise in the device tree whether or not those features are available to
the guest.
In some places we automatically determine whether to make a feature
available based on whether our host can support it, in most cases this is
based on limitations in the available KVM implementation.
Although we correctly advertise this to the guest, it means that host
factors might make changes to the guest visible environment which is bad:
as well as generaly reducing reproducibility, it means that a migration
between different host environments can easily go bad.
We've mostly gotten away with it because the environments considered mature
enough to be well supported (basically, KVM on POWER8) have had consistent
feature availability. But, it's still not right and some limitations on
POWER9 is going to make it more of an issue in future.
This introduces an infrastructure for defining "sPAPR capabilities". These
are set by default based on the machine version, masked by the capabilities
of the chosen cpu, but can be overriden with machine properties.
The intention is at reset time we verify that the requested capabilities
can be supported on the host (considering TCG, KVM and/or host cpu
limitations). If not we simply fail, rather than silently modifying the
advertised featureset to the guest.
This does mean that certain configurations that "worked" may now fail, but
such configurations were already more subtly broken.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Greg Kurz <groug@kaod.org>
Greg Kurz