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Re: [Qemu-devel] [PATCH for-4.1 v2] q35: Revert to kernel irqchip
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH for-4.1 v2] q35: Revert to kernel irqchip |
Date: |
Mon, 3 Jun 2019 10:06:06 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 |
On 29/05/19 05:30, Michael S. Tsirkin wrote:
> On Tue, May 14, 2019 at 02:14:41PM -0600, Alex Williamson wrote:
>> Commit b2fc91db8447 ("q35: set split kernel irqchip as default") changed
>> the default for the pc-q35-4.0 machine type to use split irqchip, which
>> turned out to have disasterous effects on vfio-pci INTx support. KVM
>> resampling irqfds are registered for handling these interrupts, but
>> these are non-functional in split irqchip mode. We can't simply test
>> for split irqchip in QEMU as userspace handling of this interrupt is a
>> significant performance regression versus KVM handling (GeForce GPUs
>> assigned to Windows VMs are non-functional without forcing MSI mode or
>> re-enabling kernel irqchip).
>>
>> The resolution is to revert the change in default irqchip mode in the
>> pc-q35-4.1 machine and create a pc-q35-4.0.1 machine for the 4.0-stable
>> branch. The qemu-q35-4.0 machine type should not be used in vfio-pci
>> configurations for devices requiring legacy INTx support without
>> explicitly modifying the VM configuration to use kernel irqchip.
>>
>> Link: https://bugs.launchpad.net/qemu/+bug/1826422
>> Fixes: b2fc91db8447 ("q35: set split kernel irqchip as default")
>> Signed-off-by: Alex Williamson <address@hidden>
>
> OK I guess but it's really a kvm patch.
> So I'd like Paolo to review and merge if appropriate.
>
> Can't say this makes me too happy. split irqchip
> has a bunch of advantages.
Yeah, me too but I don't see an alternative. I'll merge it today.
Paolo
>
>> ---
>> hw/core/machine.c | 3 +++
>> hw/i386/pc.c | 3 +++
>> hw/i386/pc_q35.c | 16 ++++++++++++++--
>> include/hw/boards.h | 3 +++
>> include/hw/i386/pc.h | 3 +++
>> 5 files changed, 26 insertions(+), 2 deletions(-)
>>
>> diff --git a/hw/core/machine.c b/hw/core/machine.c
>> index 5d046a43e3d2..e41e6698ac9f 100644
>> --- a/hw/core/machine.c
>> +++ b/hw/core/machine.c
>> @@ -24,6 +24,9 @@
>> #include "hw/pci/pci.h"
>> #include "hw/mem/nvdimm.h"
>>
>> +GlobalProperty hw_compat_4_0_1[] = {};
>> +const size_t hw_compat_4_0_1_len = G_N_ELEMENTS(hw_compat_4_0_1);
>> +
>> GlobalProperty hw_compat_4_0[] = {};
>> const size_t hw_compat_4_0_len = G_N_ELEMENTS(hw_compat_4_0);
>>
>> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
>> index d98b737b8f3b..b5311e7e2bd5 100644
>> --- a/hw/i386/pc.c
>> +++ b/hw/i386/pc.c
>> @@ -115,6 +115,9 @@ struct hpet_fw_config hpet_cfg = {.count = UINT8_MAX};
>> /* Physical Address of PVH entry point read from kernel ELF NOTE */
>> static size_t pvh_start_addr;
>>
>> +GlobalProperty pc_compat_4_0_1[] = {};
>> +const size_t pc_compat_4_0_1_len = G_N_ELEMENTS(pc_compat_4_0_1);
>> +
>> GlobalProperty pc_compat_4_0[] = {};
>> const size_t pc_compat_4_0_len = G_N_ELEMENTS(pc_compat_4_0);
>>
>> diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
>> index 37dd350511a9..dcddc6466200 100644
>> --- a/hw/i386/pc_q35.c
>> +++ b/hw/i386/pc_q35.c
>> @@ -357,7 +357,7 @@ static void pc_q35_machine_options(MachineClass *m)
>> m->units_per_default_bus = 1;
>> m->default_machine_opts = "firmware=bios-256k.bin";
>> m->default_display = "std";
>> - m->default_kernel_irqchip_split = true;
>> + m->default_kernel_irqchip_split = false;
>> m->no_floppy = 1;
>> machine_class_allow_dynamic_sysbus_dev(m, TYPE_AMD_IOMMU_DEVICE);
>> machine_class_allow_dynamic_sysbus_dev(m, TYPE_INTEL_IOMMU_DEVICE);
>> @@ -374,10 +374,22 @@ static void pc_q35_4_1_machine_options(MachineClass *m)
>> DEFINE_Q35_MACHINE(v4_1, "pc-q35-4.1", NULL,
>> pc_q35_4_1_machine_options);
>>
>> -static void pc_q35_4_0_machine_options(MachineClass *m)
>> +static void pc_q35_4_0_1_machine_options(MachineClass *m)
>> {
>> pc_q35_4_1_machine_options(m);
>> m->alias = NULL;
>> + compat_props_add(m->compat_props, hw_compat_4_0_1, hw_compat_4_0_1_len);
>> + compat_props_add(m->compat_props, pc_compat_4_0_1, pc_compat_4_0_1_len);
>> +}
>> +
>> +DEFINE_Q35_MACHINE(v4_0_1, "pc-q35-4.0.1", NULL,
>> + pc_q35_4_0_1_machine_options);
>> +
>> +static void pc_q35_4_0_machine_options(MachineClass *m)
>> +{
>> + pc_q35_4_0_1_machine_options(m);
>> + m->default_kernel_irqchip_split = true;
>> + m->alias = NULL;
>> compat_props_add(m->compat_props, hw_compat_4_0, hw_compat_4_0_len);
>> compat_props_add(m->compat_props, pc_compat_4_0, pc_compat_4_0_len);
>> }
>> diff --git a/include/hw/boards.h b/include/hw/boards.h
>> index 6f7916f88f02..6ff02bf3e472 100644
>> --- a/include/hw/boards.h
>> +++ b/include/hw/boards.h
>> @@ -292,6 +292,9 @@ struct MachineState {
>> } \
>> type_init(machine_initfn##_register_types)
>>
>> +extern GlobalProperty hw_compat_4_0_1[];
>> +extern const size_t hw_compat_4_0_1_len;
>> +
>> extern GlobalProperty hw_compat_4_0[];
>> extern const size_t hw_compat_4_0_len;
>>
>> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
>> index 43df7230a22b..5d5636241e34 100644
>> --- a/include/hw/i386/pc.h
>> +++ b/include/hw/i386/pc.h
>> @@ -293,6 +293,9 @@ int e820_add_entry(uint64_t, uint64_t, uint32_t);
>> int e820_get_num_entries(void);
>> bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *);
>>
>> +extern GlobalProperty pc_compat_4_0_1[];
>> +extern const size_t pc_compat_4_0_1_len;
>> +
>> extern GlobalProperty pc_compat_4_0[];
>> extern const size_t pc_compat_4_0_len;
>>
- Re: [Qemu-devel] [PATCH for-4.1 v2] q35: Revert to kernel irqchip,
Paolo Bonzini <=