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Re: [Qemu-ppc] [RFC for-2.12 7/8] spapr: Handle VMX/VSX presence as an s
From: |
Greg Kurz |
Subject: |
Re: [Qemu-ppc] [RFC for-2.12 7/8] spapr: Handle VMX/VSX presence as an spapr capability flag |
Date: |
Wed, 13 Dec 2017 10:35:32 +0100 |
On Wed, 13 Dec 2017 12:51:37 +1100
David Gibson <address@hidden> wrote:
> On Tue, Dec 12, 2017 at 01:54:36PM +0100, Greg Kurz wrote:
> > On Mon, 11 Dec 2017 18:08:07 +1100
> > David Gibson <address@hidden> wrote:
> >
> > > 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 <address@hidden>
> > > ---
> >
> > Just one nit, see below, but anyway:
> >
> > Reviewed-by: Greg Kurz <address@hidden>
> >
> >
> > > hw/ppc/spapr.c | 18 ++++++++++--------
> > > hw/ppc/spapr_caps.c | 24 ++++++++++++++++++++++++
> > > include/hw/ppc/spapr.h | 3 +++
> > > 3 files changed, 37 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > > index e206825ed9..6b37511e8f 100644
> > > --- a/hw/ppc/spapr.c
> > > +++ b/hw/ppc/spapr.c
> > > @@ -556,14 +556,16 @@ static void spapr_populate_cpu_dt(CPUState *cs,
> > > void *fdt, int offset,
> > > segs, sizeof(segs))));
> > > }
> > >
> > > - /* Advertise VMX/VSX (vector extensions) if available
> > > - * 0 / no property == no vector extensions
> > > + /* Advertise VSX (vector extensions) if available
> > > * 1 == VMX / Altivec available
> > > - * 2 == VSX available */
> > > - if (env->insns_flags & PPC_ALTIVEC) {
> > > - uint32_t vmx = (env->insns_flags2 & PPC2_VSX) ? 2 : 1;
> > > -
> > > - _FDT((fdt_setprop_cell(fdt, offset, "ibm,vmx", vmx)));
> > > + * 2 == VSX available
> > > + *
> > > + * Only CPUs for which we create core types in spapr_cpu_core.c
> > > + * are possible, and all of those have VMX */
> > > + if (spapr_has_cap(spapr, SPAPR_CAP_VSX)) {
> > > + _FDT((fdt_setprop_cell(fdt, offset, "ibm,vmx", 2)));
> >
> > Maybe a good opportunity to drop the extra parens since the _FDT() macro
> > already adds them around its argument.
> >
> > #define _FDT(exp) \
> > do { \
> > int ret = (exp); \
>
> Uh, yeah, that won't work. The extra parens are so that the macro
> considers the whole string inside as a single argument, even if it
> includes ',' characters, which it usually will.
>
Hmm... we have a bunch of other _FDT() call sites where we do without the
extra parens. No big deal anyway.
> >
> > > + } else {
> > > + _FDT((fdt_setprop_cell(fdt, offset, "ibm,vmx", 1)));
> > > }
> > >
> > > /* Advertise DFP (Decimal Floating Point) if available
> > > @@ -3829,7 +3831,7 @@ static void spapr_machine_class_init(ObjectClass
> > > *oc, void *data)
> > > */
> > > mc->numa_mem_align_shift = 28;
> > >
> > > - smc->default_caps = spapr_caps(SPAPR_CAP_HTM);
> > > + smc->default_caps = spapr_caps(SPAPR_CAP_HTM | SPAPR_CAP_VSX);
> > > spapr_capability_properties(smc, &error_abort);
> > > }
> > >
> > > diff --git a/hw/ppc/spapr_caps.c b/hw/ppc/spapr_caps.c
> > > index 6bba04d60e..b19a9f4417 100644
> > > --- a/hw/ppc/spapr_caps.c
> > > +++ b/hw/ppc/spapr_caps.c
> > > @@ -44,6 +44,11 @@ static sPAPRCapabilityInfo capability_table[] = {
> > > .description = "Allow Hardware Transactional Memory (HTM)",
> > > .bit = SPAPR_CAP_HTM,
> > > },
> > > + {
> > > + .name = "vsx",
> > > + .description = "Allow Vector Scalar Extensions (VSX)",
> > > + .bit = SPAPR_CAP_VSX,
> > > + },
> > > };
> > >
> > > static sPAPRCapabilities default_caps_with_cpu(sPAPRMachineState *spapr,
> > > CPUState *cs)
> > > @@ -59,6 +64,11 @@ static sPAPRCapabilities
> > > default_caps_with_cpu(sPAPRMachineState *spapr, CPUStat
> > > caps.mask &= ~SPAPR_CAP_HTM;
> > > }
> > >
> > > + if (!ppc_check_compat(cpu, CPU_POWERPC_LOGICAL_2_06,
> > > + 0, spapr->max_compat_pvr)) {
> > > + caps.mask &= ~SPAPR_CAP_VSX;
> > > + }
> > > +
> > > return caps;
> > > }
> > >
> > > @@ -149,6 +159,8 @@ const VMStateDescription vmstate_spapr_caps = {
> > >
> > > static void spapr_allow_caps(sPAPRMachineState *spapr, Error **errp)
> > > {
> > > + PowerPCCPU *cpu = POWERPC_CPU(first_cpu);
> > > + CPUPPCState *env = &cpu->env;
> > > Error *err = NULL;
> > >
> > > if (spapr_has_cap(spapr, SPAPR_CAP_HTM)) {
> > > @@ -164,6 +176,14 @@ static void spapr_allow_caps(sPAPRMachineState
> > > *spapr, Error **errp)
> > > }
> > > }
> > >
> > > + g_assert(env->insns_flags & PPC_ALTIVEC);
> > > + if (spapr_has_cap(spapr, SPAPR_CAP_VSX)) {
> > > + if (!(env->insns_flags2 & PPC2_VSX)) {
> > > + error_setg(&err, "VSX support not available, try
> > > cap-vsx=off");
> > > + goto out;
> > > + }
> > > + }
> > > +
> > > out:
> > > if (err) {
> > > error_propagate(errp, err);
> > > @@ -175,6 +195,10 @@ static void spapr_enforce_caps(sPAPRMachineState
> > > *spapr, Error **errp)
> > > if (!spapr_has_cap(spapr, SPAPR_CAP_HTM)) {
> > > /* TODO: Tell KVM not to allow HTM instructions */
> > > }
> > > +
> > > + if (!spapr_has_cap(spapr, SPAPR_CAP_VSX)) {
> > > + /* TODO: Any way to disable VSX? */
> > > + }
> > > }
> > >
> > > void spapr_caps_reset(sPAPRMachineState *spapr)
> > > diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> > > index 9b80fe72ed..4c173cb40c 100644
> > > --- a/include/hw/ppc/spapr.h
> > > +++ b/include/hw/ppc/spapr.h
> > > @@ -59,6 +59,9 @@ typedef enum {
> > > /* Hardware Transactional Memory */
> > > #define SPAPR_CAP_HTM 0x0000000000000001ULL
> > >
> > > +/* Vector Scalar Extensions */
> > > +#define SPAPR_CAP_VSX 0x0000000000000002ULL
> > > +
> > > typedef struct sPAPRCapabilities sPAPRCapabilities;
> > > struct sPAPRCapabilities {
> > > uint64_t mask;
> >
>
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- Re: [Qemu-ppc] [RFC for-2.12 1/8] spapr: Rename machine init functions for clarity, (continued)
[Qemu-ppc] [RFC for-2.12 6/8] target/ppc: Clean up probing of VMX, VSX and DFP availability on KVM, David Gibson, 2017/12/11
[Qemu-ppc] [RFC for-2.12 4/8] spapr: Validate capabilities on migration, David Gibson, 2017/12/11
[Qemu-ppc] [RFC for-2.12 8/8] spapr: Handle Decimal Floating Point (DFP) as an optional capability, David Gibson, 2017/12/11