We recently had some discussions that were sidetracked for a while, because
nearly everyone misapprehended the purpose of the 'max_threads' field in
the compatiblity modes table. It's all about guest expectations, not host
expectations or support (that's handled elsewhere).
In an attempt to avoid a repeat of that confusion, rename the field to
'max_vthreads' and add an explanatory comment.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Jose Ricardo Ziviani <joserz@linux.vnet.ibm.com>
Increases the max smt mode to 8 for Power9. That's because KVM supports
smt emulation in this platform so QEMU should allow users to use it as
well.
Today if we try to pass -smp ...,threads=8, QEMU will silently truncate
it to smt4 mode and may cause a crash if we try to perform a cpu
hotplug.
Signed-off-by: Jose Ricardo Ziviani <joserz@linux.vnet.ibm.com>
[dwg: Added an explanatory comment]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
While trying to make KVM PR usable again, commit 5dfaa532ae introduced a
regression: the current compat_pvr value is passed to KVM instead of the
new one. This means that we always pass 0 instead of the max-cpu-compat
PVR during the initial machine reset. And at CAS time, we either pass
the PVR from the command line or even don't call kvmppc_set_compat() at
all, ie, the PCR will not be set as expected.
For example if we start a big endian fedora26 guest in power7 compat
mode on a POWER8 host, we get this in the guest:
$ cat /proc/cpuinfo
processor : 0
cpu : POWER7 (architected), altivec supported
clock : 4024.000000MHz
revision : 2.0 (pvr 004d 0200)
timebase : 512000000
platform : pSeries
model : IBM pSeries (emulated by qemu)
machine : CHRP IBM pSeries (emulated by qemu)
MMU : Hash
but the guest can still execute POWER8 instructions, and the following
program succeeds:
int main()
{
asm("vncipher 0,0,0"); // ISA 2.07 instruction
}
Let's pass the new compat_pvr to kvmppc_set_compat() and the program fails
with SIGILL as expected.
Reported-by: Nageswara R Sastry <rnsastry@linux.vnet.ibm.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
When running in KVM PR mode, kvmppc_set_compat() always fail because the
current PR implementation doesn't handle KVM_REG_PPC_ARCH_COMPAT. Now that
the machine code inconditionally calls ppc_set_compat_all() at reset time
to restore the compat mode default value (commit 66d5c492dd), it is
impossible to start a guest with PR:
qemu-system-ppc64: Unable to set CPU compatibility mode in KVM:
Invalid argument
A tentative patch [1] was recently sent by Suraj to address the issue, but
it would prevent the compat mode to be turned off on reset. And we really
don't want to explicitely check for KVM PR. During the patch's review,
David suggested that we should only call the KVM ioctl() if the compat
PVR changes. This allows at least to run with KVM PR, provided no compat
mode is requested from the command line (which should be the case when
running PR nested). This is what this patch does.
While here, we also fix the side effect where KVM would fail but we would
change the CPU state in QEMU anyway.
[1] http://patchwork.ozlabs.org/patch/782039/
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Server class POWER CPUs have a "compat" property, which is used to set the
backwards compatibility mode for the processor. However, this only makes
sense for machine types which don't give the guest access to hypervisor
privilege - otherwise the compatibility level is under the guest's control.
To reflect this, this removes the CPU 'compat' property and instead
creates a 'max-cpu-compat' property on the pseries machine. Strictly
speaking this breaks compatibility, but AFAIK the 'compat' option was
never (directly) used with -device or device_add.
The option was used with -cpu. So, to maintain compatibility, this
patch adds a hack to the cpu option parsing to strip out any compat
options supplied with -cpu and set them on the machine property
instead of the now deprecated cpu property.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Tested-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Tested-by: Greg Kurz <groug@kaod.org>
Tested-by: Andrea Bolognani <abologna@redhat.com>
compat_table contains the list of logical pvr compat modes which a cpu can
operate in. It is a list of struct CompatInfo which contains the given pvr
value for a compat mode, the pcr bits which should be set to operate in
that compat mode, the pcr level which must be present in pcr_supported for
a processor to support that compat mode and the max threads possible in
that compat mode.
Add an entry for the POWER9/ISAv3.00 logical pvr which represents a
processor running with support for logical pvr 0x0f000005. A processor
running in this mode should have PCR_COMPAT_3_00 set in the pcr (if
available in pcr_mask) and should have PCR_COMPAT_3_00 in pcr_supported
to indicate that it is capable of running in this compat mode.
Also add PCR_COMPAT_3_00 to the bits which must be set for all previous
compat modes. Since no processor models contain this bit yet in pcr_mask
it will never be set, but this ensures we don't forget to in the future.
Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Once a compatiblity mode is negotiated with the guest,
h_client_architecture_support() uses run_on_cpu() to update each CPU to
the new mode. We're going to want this logic somewhere else shortly,
so make a helper function to do this global update.
We put it in target-ppc/compat.c - it makes as much sense at the CPU level
as it does at the machine level. We also move the cpu_synchronize_state()
into ppc_set_compat(), since it doesn't really make any sense to call that
without synchronizing state.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Current ppc_set_compat() will attempt to set any compatiblity mode
specified, regardless of whether it's available on the CPU. The caller is
expected to make sure it is setting a possible mode, which is awkwward
because most of the information to make that decision is at the CPU level.
This begins to clean this up by introducing a ppc_check_compat() function
which will determine if a given compatiblity mode is supported on a CPU
(and also whether it lies within specified minimum and maximum compat
levels, which will be useful later). It also contains an assertion that
the CPU has a "virtual hypervisor"[1], that is, that the guest isn't
permitted to execute hypervisor privilege code. Without that, the guest
would own the PCR and so could override any mode set here. Only machine
types which use a virtual hypervisor (i.e. 'pseries') should use
ppc_check_compat().
ppc_set_compat() is modified to validate the compatibility mode it is given
and fail if it's not available on this CPU.
[1] Or user-only mode, which also obviously doesn't allow access to the
hypervisor privileged PCR. We don't use that now, but could in future.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
To continue consolidation of compatibility mode information, this rewrites
the ppc_get_compat_smt_threads() function using the table of compatiblity
modes in target-ppc/compat.c.
It's not a direct replacement, the new ppc_compat_max_threads() function
has simpler semantics - it just returns the number of threads the cpu
model has, taking into account any compatiblity mode it is in.
This no longer takes into account kvmppc_smt_threads() as the previous
version did. That check wasn't useful because we check in
ppc_cpu_realizefn() that CPUs aren't instantiated with more threads
than kvm allows (or if we didn't things will already be broken and
this won't make it any worse).
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
This rewrites the ppc_set_compat() function so that instead of open coding
the various compatibility modes, it reads the relevant data from a table.
This is a first step in consolidating the information on compatibility
modes scattered across the code into a single place.
It also makes one change to the logic. The old code masked the bits
to be set in the PCR (Processor Compatibility Register) by which bits
are valid on the host CPU. This made no sense, since it was done
regardless of whether our guest CPU was the same as the host CPU or
not. Furthermore, the actual PCR bits are only relevant for TCG[1] -
KVM instead uses the compatibility mode we tell it in
kvmppc_set_compat(). When using TCG host cpu information usually
isn't even present.
While we're at it, we put the new implementation in a new file to make the
enormous translate_init.c a little smaller.
[1] Actually it doesn't even do anything in TCG, but it will if / when we
get to implementing compatibility mode logic at that level.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
