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

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

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.

Thanks,
Quang Minh.