Comment 0 for bug 1786241

Got new notebook ACER Nitro AN515-42 with AMD Ryzen 5 2400U processor and Radeon Vega 8 Mobile Gfx.
Original OS on SSD is Linpus Lite.
uname -a# Linux 4.2.01p_mmc #5 SMP i686 athlon i386 GNU/Linux
Linpus is running in text mode only.
GRUB parameters are : kernel /boot/vmlinuz ro root= nolapic_timer loglevel=0 acpi_osi=Linux pcie_aspm=off acpi=copy_dsdt pci=nocrs irqpoll quiet
I've decided to install UBUNTU MATE 18.04 on laptop.
Image ubuntu-mate-18.04-desktop-amd64.iso had been downloaded and installed on flash drive with rufus.
Laptop doesn't have a CD/DVD drive.
Secure boot was switched off in BIOS and boot from flash drive was selected.
I've selected UBUNTU try option in GRUB to test on my laptop.
Boot of kernel fail with many similar messages on screen about "soft lockup - CPU#4 stuck for 23s".
UBUNTU Mate install option had produced same error.
I've installed Windows 10 trial to test the laptop - it is working good.
I've downloaded BIOS update utility for Windows 10 only from ACER and I'd updated BIOS from v1.05 to v.1.08. No changes in Windows.
The UBUNTU MATE setup still making same errors.
I've tested ubuntu-mate-16.04-desktop-amd64.iso and ubuntu-mate-18.04.1-desktop-amd64.iso with same errors.
I've search WEB and found working solution for me with GRUB startup option "rcu_nocbs=0-7" cause my AMD got 4 cores/ 8 threads.
Second error during installation is related to ACER BIOS ACPI. UBUNTU startup fails again.
GRUB boot option acpi=off didn't work.
GRUB boot options from original Linpus didn't work.
Found in WEB working solution for me with GRUB startup option ivrs_ioapic[4]=00:14.0 ivrs_ioapic[5]=00:00.2
I've managed to install UBUNTU MATE 18.04.1 on my laptop.
I've managed to install proprietary AMD driver 18.20 for Vega video chipset.
UBUNTU MAte is running but still is getting some errors and X freeze some time - I will make extra bug report.
I'm reporting from my new laptop.
Copy of LOG files are attached.