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([2804:431:c7c7:e12e:158d:880c:57b0:bfdd]) by smtp.gmail.com with ESMTPSA id b12sm8229201ilc.21.2021.01.08.16.11.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 08 Jan 2021 16:11:53 -0800 (PST) Subject: Re: [PATCH] spapr: Improve handling of memory unplug with old guests To: Greg Kurz , qemu-devel@nongnu.org References: <161012708715.801107.11418801796987916516.stgit@bahia.lan> From: Daniel Henrique Barboza Message-ID: Date: Fri, 8 Jan 2021 21:11:50 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <161012708715.801107.11418801796987916516.stgit@bahia.lan> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::12b; envelope-from=danielhb413@gmail.com; helo=mail-il1-x12b.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_ENVFROM_END_DIGIT=0.25, FREEMAIL_FROM=0.001, NICE_REPLY_A=-0.241, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-ppc@nongnu.org, David Gibson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 1/8/21 2:31 PM, Greg Kurz wrote: > Since commit 1e8b5b1aa16b ("spapr: Allow memory unplug to always succeed") > trying to unplug memory from a guest that doesn't support it (eg. rhel6) > no longer generates an error like it used to. Instead, it leaves the > memory around : only a subsequent reboot or manual use of drmgr within > the guest can complete the hot-unplug sequence. A flag was added to > SpaprMachineClass so that this new behavior only applies to the default > machine type. > > We can do better. CAS processes all pending hot-unplug requests. This > means that we don't really care about what the guest supports if > the hot-unplug request happens before CAS. > > All guests that we care for, even old ones, set enough bits in OV5 > that lead to a non-empty bitmap in spapr->ov5_cas. Use that as a > heuristic to decide if CAS has already occured or not. > > Always accept unplug requests that happen before CAS since CAS will > process them. Restore the previous behavior of rejecting them after > CAS when we know that the guest doesn't support memory hot-unplug. > > This behavior is suitable for all machine types : this allows to > drop the pre_6_0_memory_unplug flag. > > Fixes: 1e8b5b1aa16b ("spapr: Allow memory unplug to always succeed") > Signed-off-by: Greg Kurz > --- Reviewed-by: Daniel Henrique Barboza > hw/ppc/spapr.c | 24 +++++++++++++----------- > hw/ppc/spapr_events.c | 3 +-- > hw/ppc/spapr_ovec.c | 7 +++++++ > include/hw/ppc/spapr.h | 2 +- > include/hw/ppc/spapr_ovec.h | 1 + > 5 files changed, 23 insertions(+), 14 deletions(-) > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > index 2c403b574e37..6c47466fc2f1 100644 > --- a/hw/ppc/spapr.c > +++ b/hw/ppc/spapr.c > @@ -4048,6 +4048,18 @@ static void spapr_machine_device_unplug(HotplugHandler *hotplug_dev, > } > } > > +bool spapr_memory_hot_unplug_supported(SpaprMachineState *spapr) > +{ > + return spapr_ovec_test(spapr->ov5_cas, OV5_HP_EVT) || > + /* > + * CAS will process all pending unplug requests. > + * > + * HACK: a guest could theoretically have cleared all bits in OV5, > + * but none of the guests we care for do. > + */ > + spapr_ovec_empty(spapr->ov5_cas); > +} > + > static void spapr_machine_device_unplug_request(HotplugHandler *hotplug_dev, > DeviceState *dev, Error **errp) > { > @@ -4056,16 +4068,9 @@ static void spapr_machine_device_unplug_request(HotplugHandler *hotplug_dev, > SpaprMachineClass *smc = SPAPR_MACHINE_CLASS(mc); > > if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) { > - if (!smc->pre_6_0_memory_unplug || > - spapr_ovec_test(sms->ov5_cas, OV5_HP_EVT)) { > + if (spapr_memory_hot_unplug_supported(sms)) { > spapr_memory_unplug_request(hotplug_dev, dev, errp); > } else { > - /* NOTE: this means there is a window after guest reset, prior to > - * CAS negotiation, where unplug requests will fail due to the > - * capability not being detected yet. This is a bit different than > - * the case with PCI unplug, where the events will be queued and > - * eventually handled by the guest after boot > - */ > error_setg(errp, "Memory hot unplug not supported for this guest"); > } > } else if (object_dynamic_cast(OBJECT(dev), TYPE_SPAPR_CPU_CORE)) { > @@ -4543,11 +4548,8 @@ DEFINE_SPAPR_MACHINE(6_0, "6.0", true); > */ > static void spapr_machine_5_2_class_options(MachineClass *mc) > { > - SpaprMachineClass *smc = SPAPR_MACHINE_CLASS(mc); > - > spapr_machine_6_0_class_options(mc); > compat_props_add(mc->compat_props, hw_compat_5_2, hw_compat_5_2_len); > - smc->pre_6_0_memory_unplug = true; > } > > DEFINE_SPAPR_MACHINE(5_2, "5.2", false); > diff --git a/hw/ppc/spapr_events.c b/hw/ppc/spapr_events.c > index 6aedd988b3d0..d51daedfa6e0 100644 > --- a/hw/ppc/spapr_events.c > +++ b/hw/ppc/spapr_events.c > @@ -658,8 +658,7 @@ static void spapr_hotplug_req_event(uint8_t hp_id, uint8_t hp_action, > /* we should not be using count_indexed value unless the guest > * supports dedicated hotplug event source > */ > - g_assert(!SPAPR_MACHINE_GET_CLASS(spapr)->pre_6_0_memory_unplug || > - spapr_ovec_test(spapr->ov5_cas, OV5_HP_EVT)); > + g_assert(spapr_memory_hot_unplug_supported(spapr)); > hp->drc_id.count_indexed.count = > cpu_to_be32(drc_id->count_indexed.count); > hp->drc_id.count_indexed.index = > diff --git a/hw/ppc/spapr_ovec.c b/hw/ppc/spapr_ovec.c > index dd003f1763fd..b2567caa5cf4 100644 > --- a/hw/ppc/spapr_ovec.c > +++ b/hw/ppc/spapr_ovec.c > @@ -125,6 +125,13 @@ bool spapr_ovec_test(SpaprOptionVector *ov, long bitnr) > return test_bit(bitnr, ov->bitmap) ? true : false; > } > > +bool spapr_ovec_empty(SpaprOptionVector *ov) > +{ > + g_assert(ov); > + > + return bitmap_empty(ov->bitmap, OV_MAXBITS); > +} > + > static void guest_byte_to_bitmap(uint8_t entry, unsigned long *bitmap, > long bitmap_offset) > { > diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h > index 1cc19575f548..3ad2ff713279 100644 > --- a/include/hw/ppc/spapr.h > +++ b/include/hw/ppc/spapr.h > @@ -142,7 +142,6 @@ struct SpaprMachineClass { > hwaddr rma_limit; /* clamp the RMA to this size */ > bool pre_5_1_assoc_refpoints; > bool pre_5_2_numa_associativity; > - bool pre_6_0_memory_unplug; > > bool (*phb_placement)(SpaprMachineState *spapr, uint32_t index, > uint64_t *buid, hwaddr *pio, > @@ -950,4 +949,5 @@ bool spapr_check_pagesize(SpaprMachineState *spapr, hwaddr pagesize, > > void spapr_set_all_lpcrs(target_ulong value, target_ulong mask); > hwaddr spapr_get_rtas_addr(void); > +bool spapr_memory_hot_unplug_supported(SpaprMachineState *spapr); > #endif /* HW_SPAPR_H */ > diff --git a/include/hw/ppc/spapr_ovec.h b/include/hw/ppc/spapr_ovec.h > index d4dee9e06a01..48b716a060c2 100644 > --- a/include/hw/ppc/spapr_ovec.h > +++ b/include/hw/ppc/spapr_ovec.h > @@ -71,6 +71,7 @@ void spapr_ovec_cleanup(SpaprOptionVector *ov); > void spapr_ovec_set(SpaprOptionVector *ov, long bitnr); > void spapr_ovec_clear(SpaprOptionVector *ov, long bitnr); > bool spapr_ovec_test(SpaprOptionVector *ov, long bitnr); > +bool spapr_ovec_empty(SpaprOptionVector *ov); > SpaprOptionVector *spapr_ovec_parse_vector(target_ulong table_addr, int vector); > int spapr_dt_ovec(void *fdt, int fdt_offset, > SpaprOptionVector *ov, const char *name); > > >