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File _service:tar_scm:hw-arm-virt-Expose-cold-booted-CPUs-as-MADT-GICC-Ena.patch of Package qemu
From 837b04877be49b930a2d437f55e2ae15ff820421 Mon Sep 17 00:00:00 2001 From: Salil Mehta <salil.mehta@huawei.com> Date: Sat, 23 Sep 2023 22:31:49 +0000 Subject: [PATCH] hw/arm/virt: Expose cold-booted CPUs as MADT GICC Enabled Hotpluggable CPUs MUST be exposed as 'online-capable' as per the new change. But cold booted CPUs if made 'online-capable' during boot time might not get detected in the legacy OS. Hence, can cause compatibility problems. Original Change Link: https://bugzilla.tianocore.org/show_bug.cgi?id=3706 Specification change might take time and hence disabling the support of unplugging any cold booted CPUs to preserve the compatibility with legacy OS. Signed-off-by: Salil Mehta <salil.mehta@huawei.com> --- hw/arm/virt-acpi-build.c | 19 ++++++++++++++----- hw/arm/virt.c | 16 ++++++++++++++++ include/hw/core/cpu.h | 2 ++ 3 files changed, 32 insertions(+), 5 deletions(-) diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c index c402e102c4..590afcfa98 100644 --- a/hw/arm/virt-acpi-build.c +++ b/hw/arm/virt-acpi-build.c @@ -789,17 +789,26 @@ static uint32_t virt_acpi_get_gicc_flags(CPUState *cpu) } /* - * ARM GIC CPU Interface can be 'online-capable' or 'enabled' at boot - * We MUST set 'online-capable' Bit for all hotpluggable CPUs except the - * first/boot CPU. Cold-booted CPUs without 'Id' can also be unplugged. - * Though as-of-now this is only used as a debugging feature. + * ARM GIC CPU Interface can be 'online-capable' or 'enabled' at boot. We + * MUST set 'online-capable' bit for all hotpluggable CPUs. + * Change Link: https://bugzilla.tianocore.org/show_bug.cgi?id=3706 * * UEFI ACPI Specification 6.5 * Section: 5.2.12.14. GIC CPU Interface (GICC) Structure * Table: 5.37 GICC CPU Interface Flags * Link: https://uefi.org/specs/ACPI/6.5 + * + * Cold-booted CPUs, except for the first/boot CPU, SHOULD be allowed to be + * hot(un)plug as well but for this to happen these MUST have + * 'online-capable' bit set. Later creates compatibility problem with legacy + * OS as it might ignore online-capable' bits during boot time and hence + * some CPUs might not get detected. To fix this MADT GIC CPU interface flag + * should be allowed to have both bits set i.e. 'online-capable' and + * 'Enabled' bits together. This change will require UEFI ACPI standard + * change. Till this happens exposing all cold-booted CPUs as 'enabled' only + * */ - return cpu && !cpu->cpu_index ? 1 : (1 << 3); + return cpu && cpu->cold_booted ? 1 : (1 << 3); } static void diff --git a/hw/arm/virt.c b/hw/arm/virt.c index eedff8e525..ed437ce0e8 100644 --- a/hw/arm/virt.c +++ b/hw/arm/virt.c @@ -3250,6 +3250,10 @@ static void virt_cpu_pre_plug(HotplugHandler *hotplug_dev, DeviceState *dev, * This shall be used during the init of ACPI Hotplug state and hot-unplug */ cs->acpi_persistent = true; + + if (!dev->hotplugged) { + cs->cold_booted = true; + } } static void virt_cpu_plug(HotplugHandler *hotplug_dev, DeviceState *dev, @@ -3313,6 +3317,18 @@ static void virt_cpu_unplug_request(HotplugHandler *hotplug_dev, return; } + /* + * UEFI ACPI standard change is required to make both 'enabled' and the + * 'online-capable' bit co-exist instead of being mutually exclusive. + * check virt_acpi_get_gicc_flags() for more details. + * + * Disable the unplugging of cold-booted vCPUs as a temporary mitigation. + */ + if (cs->cold_booted) { + error_setg(errp, "Hot-unplug of cold-booted CPU not supported!"); + return; + } + if (cs->cpu_index == first_cpu->cpu_index) { error_setg(errp, "Boot CPU(id%d=%d:%d:%d:%d) hot-unplug not supported", first_cpu->cpu_index, cpu->socket_id, cpu->cluster_id, diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h index 6dbe163548..ee04ee44c2 100644 --- a/include/hw/core/cpu.h +++ b/include/hw/core/cpu.h @@ -565,6 +565,8 @@ struct CPUState { uint32_t halted; int32_t exception_index; + bool cold_booted; + AccelCPUState *accel; /* shared by kvm and hvf */ bool vcpu_dirty; -- 2.27.0
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