Re: [PATCH v9 0/5] Support x2APIC mode with TCG accelerator

[Bui Quang Minh <minhquangbui99@gmail.com>]

On 11/9/23 21:32, Joao Martins wrote:
> On 09/11/2023 14:10, Bui Quang Minh wrote:
>> On 11/9/23 17:11, Santosh Shukla wrote:
>>> On 10/24/2023 8:51 PM, Bui Quang Minh wrote:
>>>> Hi everyone,
>>>>
>>>> This series implements x2APIC mode in userspace local APIC and the
>>>> RDMSR/WRMSR helper to access x2APIC registers in x2APIC mode. Intel iommu
>>>> and AMD iommu are adjusted to support x2APIC interrupt remapping. With this
>>>> series, we can now boot Linux kernel into x2APIC mode with TCG accelerator
>>>> using either Intel or AMD iommu.
>>>>
>>>> Testing to boot my own built Linux 6.3.0-rc2, the kernel successfully boot
>>>> with enabled x2APIC and can enumerate CPU with APIC ID 257
>>>>
>>>> Using Intel IOMMU
>>>>
>>>> qemu/build/qemu-system-x86_64 \
>>>>     -smp 2,maxcpus=260 \
>>>>     -cpu qemu64,x2apic=on \
>>>>     -machine q35 \
>>>>     -device intel-iommu,intremap=on,eim=on \
>>>>     -device qemu64-x86_64-cpu,x2apic=on,core-id=257,socket-id=0,thread-id=0 \
>>>>     -m 2G \
>>>>     -kernel $KERNEL_DIR \
>>>>     -append "nokaslr console=ttyS0 root=/dev/sda earlyprintk=serial
>>>> net.ifnames=0" \
>>>>     -drive file=$IMAGE_DIR,format=raw \
>>>>     -nographic \
>>>>     -s
>>>>
>>>> Using AMD IOMMU
>>>>
>>>> qemu/build/qemu-system-x86_64 \
>>>>     -smp 2,maxcpus=260 \
>>>>     -cpu qemu64,x2apic=on \
>>>>     -machine q35 \
>>>>     -device amd-iommu,intremap=on,xtsup=on \
>>>>     -device qemu64-x86_64-cpu,x2apic=on,core-id=257,socket-id=0,thread-id=0 \
>>>>     -m 2G \
>>>>     -kernel $KERNEL_DIR \
>>>>     -append "nokaslr console=ttyS0 root=/dev/sda earlyprintk=serial
>>>> net.ifnames=0" \
>>>>     -drive file=$IMAGE_DIR,format=raw \
>>>>     -nographic \
>>>>     -s
>>>>
>>>> Testing the emulated userspace APIC with kvm-unit-tests, disable test
>>>> device with this patch
>>>>
>>>> diff --git a/lib/x86/fwcfg.c b/lib/x86/fwcfg.c
>>>> index 1734afb..f56fe1c 100644
>>>> --- a/lib/x86/fwcfg.c
>>>> +++ b/lib/x86/fwcfg.c
>>>> @@ -27,6 +27,7 @@ static void read_cfg_override(void)
>>>>
>>>>           if ((str = getenv("TEST_DEVICE")))
>>>>                   no_test_device = !atol(str);
>>>> +       no_test_device = true;
>>>>
>>>>           if ((str = getenv("MEMLIMIT")))
>>>>                   fw_override[FW_CFG_MAX_RAM] = atol(str) * 1024 * 1024;
>>>>
>>>> ~ env QEMU=/home/minh/Desktop/oss/qemu/build/qemu-system-x86_64 ACCEL=tcg \
>>>> ./run_tests.sh -v -g apic
>>>>
>>>> TESTNAME=apic-split TIMEOUT=90s ACCEL=tcg ./x86/run x86/apic.flat -smp 2
>>>> -cpu qemu64,+x2apic,+tsc-deadline -machine kernel_irqchip=split FAIL
>>>> apic-split (54 tests, 8 unexpected failures, 1 skipped)
>>>> TESTNAME=ioapic-split TIMEOUT=90s ACCEL=tcg ./x86/run x86/ioapic.flat -smp
>>>> 1 -cpu qemu64 -machine kernel_irqchip=split PASS ioapic-split (19 tests)
>>>> TESTNAME=x2apic TIMEOUT=30 ACCEL=tcg ./x86/run x86/apic.flat -smp 2 -cpu
>>>> qemu64,+x2apic,+tsc-deadline FAIL x2apic (54 tests, 8 unexpected failures,
>>>> 1 skipped) TESTNAME=xapic TIMEOUT=60 ACCEL=tcg ./x86/run x86/apic.flat -smp
>>>> 2 -cpu qemu64,-x2apic,+tsc-deadline -machine pit=off FAIL xapic (43 tests,
>>>> 6 unexpected failures, 2 skipped)
>>>>
>>>>     FAIL: apic_disable: *0xfee00030: 50014
>>>>     FAIL: apic_disable: *0xfee00080: f0
>>>>     FAIL: apic_disable: *0xfee00030: 50014
>>>>     FAIL: apic_disable: *0xfee00080: f0
>>>>     FAIL: apicbase: relocate apic
>>>>
>>>> These errors are because we don't disable MMIO region when switching to
>>>> x2APIC and don't support relocate MMIO region yet. This is a problem
>>>> because, MMIO region is the same for all CPUs, in order to support these we
>>>> need to figure out how to allocate and manage different MMIO regions for
>>>> each CPUs. This can be an improvement in the future.
>>>>
>>>>     FAIL: nmi-after-sti
>>>>     FAIL: multiple nmi
>>>>
>>>> These errors are in the way we handle CPU_INTERRUPT_NMI in core TCG.
>>>>
>>>>     FAIL: TMCCT should stay at zero
>>>>
>>>> This error is related to APIC timer which should be addressed in separate
>>>> patch.
>>>>
>>>> Version 9 changes,
>>>
>>> Hi Bui,
>>>
>>> I have tested v9 on EPYC-Genoa system with kvm acceleration mode on, I could
>>> see > 255 vCPU for Linux and Windows Guest.
>>>
>>> Tested-by: Santosh Shukla <Santosh.Shukla@amd.com>
>>
>> Hi Santosh,
>>
>> With KVM enabled, you may be using the in kernel APIC from KVM not the emulated
>> APIC in userspace as in this series.
>>
> 
> Your XTSup code isn't necessarily userspace APIC specific. You can have
> accel=kvm with split irqchip and things will still work. I suspect that's how
> Santosh tested it.

Ah, I got it. Thanks Santosh, Joao.
Quang Minh.