From: David Gibson <david@gibson.dropbear.id.au>
To: Greg Kurz <groug@kaod.org>
Cc: "Daniel Henrique Barboza" <danielhb@linux.ibm.com>,
qemu-ppc@nongnu.org, "Cédric Le Goater" <clg@kaod.org>,
qemu-devel@nongnu.org
Subject: Re: [PATCH for-5.2 3/5] ppc/xive: Introduce dedicated kvm_irqchip_in_kernel() wrappers
Date: Thu, 6 Aug 2020 15:08:35 +1000 [thread overview]
Message-ID: <20200806050835.GC100968@yekko.fritz.box> (raw)
In-Reply-To: <159664893734.638781.14358602267403682394.stgit@bahia.lan>
[-- Attachment #1: Type: text/plain, Size: 12965 bytes --]
On Wed, Aug 05, 2020 at 07:35:37PM +0200, 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. Introduce helpers to access the underlying
> fd for various XIVE types and call them with a kvm_irqchip_in_kernel()
> guard : this allows the compiler to optimize the kvmppc_xive_* calls
> out if CONFIG_KVM isn't defined, thus avoiding the need for stubs.
>
> Signed-off-by: Greg Kurz <groug@kaod.org>
> ---
> hw/intc/spapr_xive.c | 39 +++++++++++++++++++++++++--------------
> hw/intc/spapr_xive_kvm.c | 15 +++++++++++++++
> hw/intc/xive.c | 30 +++++++++++++++++++++++-------
> include/hw/ppc/spapr_xive.h | 1 +
> include/hw/ppc/xive.h | 2 ++
> 5 files changed, 66 insertions(+), 21 deletions(-)
>
> diff --git a/hw/intc/spapr_xive.c b/hw/intc/spapr_xive.c
> index 89c8cd96670b..98e6489fb16d 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 kvmppc_xive_in_kernel(xive) \
> + (kvm_irqchip_in_kernel() && kvmppc_xive_kernel_irqchip(xive))
This all seems like a good idea, my only concern is that the semantic
difference between kvmppc_xive_in_kernel() and
kvmppc_xive_kernel_irqchip() is pretty subtle and non-obvious (and
likewise for the tctx and xsrc variations).
We're right in the XIVE implementation, so I suggest you eliminate the
kvmppc_xive_kernel_irqchip() etc. wrappers and just open code a check
on the fd in kvmppc_xive_in_kernel() etc.
> +
> void spapr_xive_pic_print_info(SpaprXive *xive, Monitor *mon)
> {
> XiveSource *xsrc = &xive->source;
> int i;
>
> - if (kvm_irqchip_in_kernel()) {
> + if (kvmppc_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 (kvmppc_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 (kvmppc_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 (kvmppc_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 (kvmppc_xive_in_kernel(xive)) {
> kvmppc_xive_source_set_irq(&xive->source, irq, val);
> } else {
> xive_source_set_irq(&xive->source, irq, val);
> @@ -749,7 +760,7 @@ static void spapr_xive_deactivate(SpaprInterruptController *intc)
>
> spapr_xive_mmio_set_enabled(xive, false);
>
> - if (kvm_irqchip_in_kernel()) {
> + if (kvmppc_xive_in_kernel(xive)) {
> kvmppc_xive_disconnect(intc);
> }
> }
> @@ -1058,7 +1069,7 @@ 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 (kvmppc_xive_in_kernel(xive)) {
> Error *local_err = NULL;
>
> kvmppc_xive_set_source_config(xive, lisn, &new_eas, &local_err);
> @@ -1379,7 +1390,7 @@ static target_ulong h_int_set_queue_config(PowerPCCPU *cpu,
> */
>
> out:
> - if (kvm_irqchip_in_kernel()) {
> + if (kvmppc_xive_in_kernel(xive)) {
> Error *local_err = NULL;
>
> kvmppc_xive_set_queue_config(xive, end_blk, end_idx, &end, &local_err);
> @@ -1480,7 +1491,7 @@ static target_ulong h_int_get_queue_config(PowerPCCPU *cpu,
> args[2] = 0;
> }
>
> - if (kvm_irqchip_in_kernel()) {
> + if (kvmppc_xive_in_kernel(xive)) {
> Error *local_err = NULL;
>
> kvmppc_xive_get_queue_config(xive, end_blk, end_idx, end, &local_err);
> @@ -1642,7 +1653,7 @@ static target_ulong h_int_esb(PowerPCCPU *cpu,
> return H_P3;
> }
>
> - if (kvm_irqchip_in_kernel()) {
> + if (kvmppc_xive_in_kernel(xive)) {
> args[0] = kvmppc_xive_esb_rw(xsrc, lisn, offset, data,
> flags & SPAPR_XIVE_ESB_STORE);
> } else {
> @@ -1717,7 +1728,7 @@ static target_ulong h_int_sync(PowerPCCPU *cpu,
> * under KVM
> */
>
> - if (kvm_irqchip_in_kernel()) {
> + if (kvmppc_xive_in_kernel(xive)) {
> Error *local_err = NULL;
>
> kvmppc_xive_sync_source(xive, lisn, &local_err);
> @@ -1761,7 +1772,7 @@ static target_ulong h_int_reset(PowerPCCPU *cpu,
>
> device_legacy_reset(DEVICE(xive));
>
> - if (kvm_irqchip_in_kernel()) {
> + if (kvmppc_xive_in_kernel(xive)) {
> Error *local_err = NULL;
>
> kvmppc_xive_reset(xive, &local_err);
> diff --git a/hw/intc/spapr_xive_kvm.c b/hw/intc/spapr_xive_kvm.c
> index 893a1ee77e70..a9657e2b0cda 100644
> --- a/hw/intc/spapr_xive_kvm.c
> +++ b/hw/intc/spapr_xive_kvm.c
> @@ -889,3 +889,18 @@ void kvmppc_xive_disconnect(SpaprInterruptController *intc)
> xive->change = NULL;
> }
> }
> +
> +bool kvmppc_xive_kernel_irqchip(SpaprXive *xive)
> +{
> + return xive->fd != -1;
> +}
> +
> +bool kvmppc_xive_kernel_irqchip_tctx(XiveTCTX *tctx)
> +{
> + return kvmppc_xive_kernel_irqchip(SPAPR_XIVE(tctx->xptr));
> +}
> +
> +bool kvmppc_xive_kernel_irqchip_xsrc(XiveSource *xsrc)
> +{
> + return kvmppc_xive_kernel_irqchip(SPAPR_XIVE(xsrc->xive));
> +}
> diff --git a/hw/intc/xive.c b/hw/intc/xive.c
> index 9b55e0356c62..2e1af4530dc5 100644
> --- a/hw/intc/xive.c
> +++ b/hw/intc/xive.c
> @@ -592,6 +592,13 @@ 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 kvmppc_xive_in_kernel_tctx(tctx) \
> + (kvm_irqchip_in_kernel() && kvmppc_xive_kernel_irqchip_tctx(tctx))
> +
> void xive_tctx_pic_print_info(XiveTCTX *tctx, Monitor *mon)
> {
> int cpu_index;
> @@ -606,7 +613,7 @@ 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 (kvmppc_xive_in_kernel_tctx(tctx)) {
> Error *local_err = NULL;
>
> kvmppc_xive_cpu_synchronize_state(tctx, &local_err);
> @@ -671,7 +678,7 @@ 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 (kvmppc_xive_in_kernel_tctx(tctx)) {
> kvmppc_xive_cpu_connect(tctx, &local_err);
> if (local_err) {
> error_propagate(errp, local_err);
> @@ -682,10 +689,11 @@ 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 (kvmppc_xive_in_kernel_tctx(tctx)) {
> + kvmppc_xive_cpu_get_state(tctx, &local_err);
> if (local_err) {
> error_report_err(local_err);
> return -1;
> @@ -697,14 +705,15 @@ 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 (kvmppc_xive_in_kernel_tctx(tctx)) {
> /*
> * 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;
> @@ -1125,6 +1134,13 @@ static void xive_source_reset(void *dev)
> memset(xsrc->status, XIVE_ESB_OFF, xsrc->nr_irqs);
> }
>
> +/*
> + * kvm_irqchip_in_kernel() will cause the compiler to turn this
> + * info a nop if CONFIG_KVM isn't defined.
> + */
> +#define kvmppc_xive_in_kernel_xsrc(xsrc) \
> + (kvm_irqchip_in_kernel() && kvmppc_xive_kernel_irqchip_xsrc(xsrc))
> +
> static void xive_source_realize(DeviceState *dev, Error **errp)
> {
> XiveSource *xsrc = XIVE_SOURCE(dev);
> @@ -1147,7 +1163,7 @@ 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 (!kvmppc_xive_in_kernel_xsrc(xsrc)) {
> 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/spapr_xive.h b/include/hw/ppc/spapr_xive.h
> index 93d09d68deb7..9fd00378ac1f 100644
> --- a/include/hw/ppc/spapr_xive.h
> +++ b/include/hw/ppc/spapr_xive.h
> @@ -94,5 +94,6 @@ void kvmppc_xive_get_queue_config(SpaprXive *xive, uint8_t end_blk,
> void kvmppc_xive_synchronize_state(SpaprXive *xive, Error **errp);
> int kvmppc_xive_pre_save(SpaprXive *xive);
> int kvmppc_xive_post_load(SpaprXive *xive, int version_id);
> +bool kvmppc_xive_kernel_irqchip(SpaprXive *xive);
>
> #endif /* PPC_SPAPR_XIVE_H */
> diff --git a/include/hw/ppc/xive.h b/include/hw/ppc/xive.h
> index 705cf48176fc..ea66e9ea9c7b 100644
> --- a/include/hw/ppc/xive.h
> +++ b/include/hw/ppc/xive.h
> @@ -484,5 +484,7 @@ void kvmppc_xive_cpu_connect(XiveTCTX *tctx, Error **errp);
> void kvmppc_xive_cpu_synchronize_state(XiveTCTX *tctx, Error **errp);
> void kvmppc_xive_cpu_get_state(XiveTCTX *tctx, Error **errp);
> void kvmppc_xive_cpu_set_state(XiveTCTX *tctx, Error **errp);
> +bool kvmppc_xive_kernel_irqchip_tctx(XiveTCTX *tctx);
> +bool kvmppc_xive_kernel_irqchip_xsrc(XiveSource *xsrc);
>
> #endif /* PPC_XIVE_H */
>
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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next prev parent reply other threads:[~2020-08-06 12:15 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-05 17:35 [PATCH for-5.2 0/5] spapr: Cleanups for XIVE and PHB Greg Kurz
2020-08-05 17:35 ` [PATCH for-5.2 1/5] spapr/xive: Fix xive->fd if kvm_create_device() fails Greg Kurz
2020-08-06 5:05 ` David Gibson
2020-08-05 17:35 ` [PATCH for-5.2 2/5] spapr/xive: Simplify kvmppc_xive_disconnect() Greg Kurz
2020-08-06 5:05 ` David Gibson
2020-08-05 17:35 ` [PATCH for-5.2 3/5] ppc/xive: Introduce dedicated kvm_irqchip_in_kernel() wrappers Greg Kurz
2020-08-06 5:08 ` David Gibson [this message]
2020-08-06 9:23 ` Greg Kurz
2020-08-05 17:35 ` [PATCH for-5.2 4/5] spapr/xive: Convert KVM device fd checks to assert() Greg Kurz
2020-08-06 5:09 ` David Gibson
2020-08-05 17:35 ` [PATCH for-5.2 5/5] spapr: Simplify error handling in spapr_phb_realize() Greg Kurz
2020-08-06 5:10 ` David Gibson
2020-08-05 17:43 ` [PATCH for-5.2 0/5] spapr: Cleanups for XIVE and PHB no-reply
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