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Re: [PATCH v2 for-5.2 3/5] ppc/xive: Introduce dedicated kvm_irqchip_in_
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From: |
Greg Kurz |
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Subject: |
Re: [PATCH v2 for-5.2 3/5] ppc/xive: Introduce dedicated kvm_irqchip_in_kernel() wrappers |
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Date: |
Fri, 7 Aug 2020 09:15:54 +0200 |
On Thu, 6 Aug 2020 19:55:29 +0200
Cédric Le Goater <clg@kaod.org> wrote:
> On 8/6/20 6:56 PM, Greg Kurz wrote:
> > Calls to the KVM XIVE device are guarded by kvm_irqchip_in_kernel(). This
> > ensures that QEMU won't try to use the device if KVM is disabled or if
> > an in-kernel irqchip isn't required.
> >
> > When using ic-mode=dual with the pseries machine, we have two possible
> > interrupt controllers: XIVE and XICS. The kvm_irqchip_in_kernel() helper
> > will return true as soon as any of the KVM device is created. It might
> > lure QEMU to think that the other one is also around, while it is not.
> > This is exactly what happens with ic-mode=dual at machine init when
> > claiming IRQ numbers, which must be done on all possible IRQ backends,
> > eg. RTAS event sources or the PHB0 LSI table : only the KVM XICS device
> > is active but we end up calling kvmppc_xive_source_reset_one() anyway,
> > which fails. This doesn't cause any trouble because of another bug :
> > kvmppc_xive_source_reset_one() lacks an error_setg() and callers don't
> > see the failure.
> >
> > Most of the other kvmppc_xive_* functions have similar xive->fd
> > checks to filter out the case when KVM XIVE isn't active. It
> > might look safer to have idempotent functions but it doesn't
> > really help to understand what's going on when debugging.
> >
> > Since we already have all the kvm_irqchip_in_kernel() in place,
> > also have the callers to check xive->fd as well before calling
> > KVM XIVE specific code. This is straight-forward for the spapr
> > specific XIVE code. Some more care is needed for the platform
> > agnostic XIVE code since it cannot access xive->fd directly.
> > Introduce new in_kernel() methods in some base XIVE classes
> > for this purpose and implement them only in spapr.
> >
> > In all cases, we still need to call kvm_irqchip_in_kernel() so that
> > compilers can optimize the kvmppc_xive_* calls away when CONFIG_KVM
> > isn't defined, thus avoiding the need for stubs.
> >
> > Signed-off-by: Greg Kurz <groug@kaod.org>
> > ---
> > v2: Introduce in_kernel() abstract methods in the base XIVE classes
> > ---
> > hw/intc/spapr_xive.c | 53
> > ++++++++++++++++++++++++++++++++++++-------------
> > hw/intc/xive.c | 28 +++++++++++++++++++-------
> > include/hw/ppc/xive.h | 2 ++
> > 3 files changed, 62 insertions(+), 21 deletions(-)
> >
> > diff --git a/hw/intc/spapr_xive.c b/hw/intc/spapr_xive.c
> > index 89c8cd96670b..cd001c580e89 100644
> > --- a/hw/intc/spapr_xive.c
> > +++ b/hw/intc/spapr_xive.c
> > @@ -148,12 +148,19 @@ static void spapr_xive_end_pic_print_info(SpaprXive
> > *xive, XiveEND *end,
> > xive_end_queue_pic_print_info(end, 6, mon);
> > }
> >
> > +/*
> > + * kvm_irqchip_in_kernel() will cause the compiler to turn this
> > + * info a nop if CONFIG_KVM isn't defined.
> > + */
> > +#define spapr_xive_in_kernel(xive) \
> > + (kvm_irqchip_in_kernel() && (xive)->fd != -1)
> > +
>
> This looks ok. SpaprXive is the userspace frontend device of
> the KVM XIVE native device in the hypervisor.
>
> > void spapr_xive_pic_print_info(SpaprXive *xive, Monitor *mon)
> > {
> > XiveSource *xsrc = &xive->source;
> > int i;
> >
> > - if (kvm_irqchip_in_kernel()) {
> > + if (spapr_xive_in_kernel(xive)) {
> > Error *local_err = NULL;
> >
> > kvmppc_xive_synchronize_state(xive, &local_err);
> > @@ -507,8 +514,10 @@ static const VMStateDescription vmstate_spapr_xive_eas
> > = {
> >
> > static int vmstate_spapr_xive_pre_save(void *opaque)
> > {
> > - if (kvm_irqchip_in_kernel()) {
> > - return kvmppc_xive_pre_save(SPAPR_XIVE(opaque));
> > + SpaprXive *xive = SPAPR_XIVE(opaque);
> > +
> > + if (spapr_xive_in_kernel(xive)) {
> > + return kvmppc_xive_pre_save(xive);
> > }
> >
> > return 0;
> > @@ -520,8 +529,10 @@ static int vmstate_spapr_xive_pre_save(void *opaque)
> > */
> > static int spapr_xive_post_load(SpaprInterruptController *intc, int
> > version_id)
> > {
> > - if (kvm_irqchip_in_kernel()) {
> > - return kvmppc_xive_post_load(SPAPR_XIVE(intc), version_id);
> > + SpaprXive *xive = SPAPR_XIVE(intc);
> > +
> > + if (spapr_xive_in_kernel(xive)) {
> > + return kvmppc_xive_post_load(xive, version_id);
> > }
> >
> > return 0;
> > @@ -564,7 +575,7 @@ static int
> > spapr_xive_claim_irq(SpaprInterruptController *intc, int lisn,
> > xive_source_irq_set_lsi(xsrc, lisn);
> > }
> >
> > - if (kvm_irqchip_in_kernel()) {
> > + if (spapr_xive_in_kernel(xive)) {
> > return kvmppc_xive_source_reset_one(xsrc, lisn, errp);
> > }
> >
> > @@ -641,7 +652,7 @@ static void spapr_xive_set_irq(SpaprInterruptController
> > *intc, int irq, int val)
> > {
> > SpaprXive *xive = SPAPR_XIVE(intc);
> >
> > - if (kvm_irqchip_in_kernel()) {
> > + if (spapr_xive_in_kernel(xive)) {
> > kvmppc_xive_source_set_irq(&xive->source, irq, val);
> > } else {
> > xive_source_set_irq(&xive->source, irq, val);
> > @@ -749,11 +760,21 @@ static void
> > spapr_xive_deactivate(SpaprInterruptController *intc)
> >
> > spapr_xive_mmio_set_enabled(xive, false);
> >
> > - if (kvm_irqchip_in_kernel()) {
> > + if (spapr_xive_in_kernel(xive)) {
> > kvmppc_xive_disconnect(intc);
> > }
> > }
> >
> > +static bool spapr_xive_in_kernel_xptr(const XivePresenter *xptr)
> > +{
> > + return spapr_xive_in_kernel(SPAPR_XIVE(xptr));
> > +}
>
> This is mostly OK, a XivePresenter is a part of the XiveRouter.
>
> > +static bool spapr_xive_in_kernel_xn(const XiveNotifier *xn)
> > +{
> > + return spapr_xive_in_kernel(SPAPR_XIVE(xn));
> > +}
>
>
> This is weird. we have other XiveNotifiers which have no relation
> with a kernel backend.
>
These other XiveNotifiers don't implement the in_kernel() method.
What's the problem ?
> > static void spapr_xive_class_init(ObjectClass *klass, void *data)
> > {
> > DeviceClass *dc = DEVICE_CLASS(klass);
> > @@ -761,6 +782,7 @@ static void spapr_xive_class_init(ObjectClass *klass,
> > void *data)
> > SpaprInterruptControllerClass *sicc = SPAPR_INTC_CLASS(klass);
> > XivePresenterClass *xpc = XIVE_PRESENTER_CLASS(klass);
> > SpaprXiveClass *sxc = SPAPR_XIVE_CLASS(klass);
> > + XiveNotifierClass *xnc = XIVE_NOTIFIER_CLASS(klass);
> >
> > dc->desc = "sPAPR XIVE Interrupt Controller";
> > device_class_set_props(dc, spapr_xive_properties);
> > @@ -788,6 +810,9 @@ static void spapr_xive_class_init(ObjectClass *klass,
> > void *data)
> > sicc->post_load = spapr_xive_post_load;
> >
> > xpc->match_nvt = spapr_xive_match_nvt;
> > + xpc->in_kernel = spapr_xive_in_kernel_xptr;
> > +
> > + xnc->in_kernel = spapr_xive_in_kernel_xn;
> > }
> >
> > static const TypeInfo spapr_xive_info = {
> > @@ -1058,7 +1083,7 @@ static target_ulong
> > h_int_set_source_config(PowerPCCPU *cpu,
> > new_eas.w = xive_set_field64(EAS_END_DATA, new_eas.w, eisn);
> > }
> >
> > - if (kvm_irqchip_in_kernel()) {
> > + if (spapr_xive_in_kernel(xive)) {
> > Error *local_err = NULL;
> >
> > kvmppc_xive_set_source_config(xive, lisn, &new_eas, &local_err);
> > @@ -1379,7 +1404,7 @@ static target_ulong h_int_set_queue_config(PowerPCCPU
> > *cpu,
> > */
> >
> > out:
> > - if (kvm_irqchip_in_kernel()) {
> > + if (spapr_xive_in_kernel(xive)) {
> > Error *local_err = NULL;
> >
> > kvmppc_xive_set_queue_config(xive, end_blk, end_idx, &end,
> > &local_err);
> > @@ -1480,7 +1505,7 @@ static target_ulong h_int_get_queue_config(PowerPCCPU
> > *cpu,
> > args[2] = 0;
> > }
> >
> > - if (kvm_irqchip_in_kernel()) {
> > + if (spapr_xive_in_kernel(xive)) {
> > Error *local_err = NULL;
> >
> > kvmppc_xive_get_queue_config(xive, end_blk, end_idx, end,
> > &local_err);
> > @@ -1642,7 +1667,7 @@ static target_ulong h_int_esb(PowerPCCPU *cpu,
> > return H_P3;
> > }
> >
> > - if (kvm_irqchip_in_kernel()) {
> > + if (spapr_xive_in_kernel(xive)) {
> > args[0] = kvmppc_xive_esb_rw(xsrc, lisn, offset, data,
> > flags & SPAPR_XIVE_ESB_STORE);
> > } else {
> > @@ -1717,7 +1742,7 @@ static target_ulong h_int_sync(PowerPCCPU *cpu,
> > * under KVM
> > */
> >
> > - if (kvm_irqchip_in_kernel()) {
> > + if (spapr_xive_in_kernel(xive)) {
> > Error *local_err = NULL;
> >
> > kvmppc_xive_sync_source(xive, lisn, &local_err);
> > @@ -1761,7 +1786,7 @@ static target_ulong h_int_reset(PowerPCCPU *cpu,
> >
> > device_legacy_reset(DEVICE(xive));
> >
> > - if (kvm_irqchip_in_kernel()) {
> > + if (spapr_xive_in_kernel(xive)) {
> > Error *local_err = NULL;
> >
> > kvmppc_xive_reset(xive, &local_err);
> > diff --git a/hw/intc/xive.c b/hw/intc/xive.c
> > index 9b55e0356c62..27d27fdc9ee4 100644
> > --- a/hw/intc/xive.c
> > +++ b/hw/intc/xive.c
> > @@ -592,6 +592,17 @@ static const char * const xive_tctx_ring_names[] = {
> > "USER", "OS", "POOL", "PHYS",
> > };
> >
> > +/*
> > + * kvm_irqchip_in_kernel() will cause the compiler to turn this
> > + * info a nop if CONFIG_KVM isn't defined.
> > + */
> > +#define xive_in_kernel(xptr) \
> > + (kvm_irqchip_in_kernel() && \
> > + ({ \
> > + XivePresenterClass *xpc = XIVE_PRESENTER_GET_CLASS(xptr); \
> > + xpc->in_kernel ? xpc->in_kernel(xptr) : false; \
> > + }))
> > +
> >
> > void xive_tctx_pic_print_info(XiveTCTX *tctx, Monitor *mon)
> > {
> > int cpu_index;
> > @@ -606,7 +617,7 @@ void xive_tctx_pic_print_info(XiveTCTX *tctx, Monitor
> > *mon)
> >
> > cpu_index = tctx->cs ? tctx->cs->cpu_index : -1;
> >
> > - if (kvm_irqchip_in_kernel()) {
> > + if (xive_in_kernel(tctx->xptr)) {
> > Error *local_err = NULL;
> >
> > kvmppc_xive_cpu_synchronize_state(tctx, &local_err);
> > @@ -671,7 +682,7 @@ static void xive_tctx_realize(DeviceState *dev, Error
> > **errp)
> > }
> >
> > /* Connect the presenter to the VCPU (required for CPU hotplug) */
> > - if (kvm_irqchip_in_kernel()) {
> > + if (xive_in_kernel(tctx->xptr)) {
> > kvmppc_xive_cpu_connect(tctx, &local_err);
> > if (local_err) {
> > error_propagate(errp, local_err);
> > @@ -682,10 +693,11 @@ static void xive_tctx_realize(DeviceState *dev, Error
> > **errp)
> >
> > static int vmstate_xive_tctx_pre_save(void *opaque)
> > {
> > + XiveTCTX *tctx = XIVE_TCTX(opaque);
> > Error *local_err = NULL;
> >
> > - if (kvm_irqchip_in_kernel()) {
> > - kvmppc_xive_cpu_get_state(XIVE_TCTX(opaque), &local_err);
> > + if (xive_in_kernel(tctx->xptr)) {
> > + kvmppc_xive_cpu_get_state(tctx, &local_err);
> > if (local_err) {
> > error_report_err(local_err);
> > return -1;
> > @@ -697,14 +709,15 @@ static int vmstate_xive_tctx_pre_save(void *opaque)
> >
> > static int vmstate_xive_tctx_post_load(void *opaque, int version_id)
> > {
> > + XiveTCTX *tctx = XIVE_TCTX(opaque);
> > Error *local_err = NULL;
> >
> > - if (kvm_irqchip_in_kernel()) {
> > + if (xive_in_kernel(tctx->xptr)) {
> > /*
> > * Required for hotplugged CPU, for which the state comes
> > * after all states of the machine.
> > */
> > - kvmppc_xive_cpu_set_state(XIVE_TCTX(opaque), &local_err);
> > + kvmppc_xive_cpu_set_state(tctx, &local_err);
> > if (local_err) {
> > error_report_err(local_err);
> > return -1;
> > @@ -1128,6 +1141,7 @@ static void xive_source_reset(void *dev)
> > static void xive_source_realize(DeviceState *dev, Error **errp)
> > {
> > XiveSource *xsrc = XIVE_SOURCE(dev);
> > + XiveNotifierClass *xnc = XIVE_NOTIFIER_GET_CLASS(xsrc->xive);
> >
> > assert(xsrc->xive);
> >
> > @@ -1147,7 +1161,7 @@ static void xive_source_realize(DeviceState *dev,
> > Error **errp)
> > xsrc->status = g_malloc0(xsrc->nr_irqs);
> > xsrc->lsi_map = bitmap_new(xsrc->nr_irqs);
> >
> > - if (!kvm_irqchip_in_kernel()) {
> > + if (!xnc->in_kernel || !xnc->in_kernel(xsrc->xive)) {
> > memory_region_init_io(&xsrc->esb_mmio, OBJECT(xsrc),
> > &xive_source_esb_ops, xsrc, "xive.esb",
> > (1ull << xsrc->esb_shift) * xsrc->nr_irqs);
> > diff --git a/include/hw/ppc/xive.h b/include/hw/ppc/xive.h
> > index 705cf48176fc..aa46e3fcf512 100644
> > --- a/include/hw/ppc/xive.h
> > +++ b/include/hw/ppc/xive.h
> > @@ -161,6 +161,7 @@ typedef struct XiveNotifier XiveNotifier;
> > typedef struct XiveNotifierClass {
> > InterfaceClass parent;
> > void (*notify)(XiveNotifier *xn, uint32_t lisn);
> > + bool (*in_kernel)(const XiveNotifier *xn);
> > } XiveNotifierClass;
> >
> > /*
> > @@ -396,6 +397,7 @@ typedef struct XivePresenterClass {
> > uint8_t nvt_blk, uint32_t nvt_idx,
> > bool cam_ignore, uint8_t priority,
> > uint32_t logic_serv, XiveTCTXMatch *match);
> > + bool (*in_kernel)(const XivePresenter *xptr);
> > } XivePresenterClass;
> >
> > int xive_presenter_tctx_match(XivePresenter *xptr, XiveTCTX *tctx,
> >
> >
>
> It seems redundant. Can we introduce a new XiveBackend QOM interface
> which would implement an in_kernel() handler ? and XiveRouter would
> inherit from it.
>
Not sure to see how it would help... the XiveRouter type isn't used
at the locations where we call kvm_irqchip_in_kernel(). Only
XivePresenter and XiveNotifier...
> C.
>
>
>
>
>