[Bug 216045] New: KVM x2APIC virtualization causes EOI to be ignored

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=216045

            Bug ID: 216045
           Summary: KVM x2APIC virtualization causes EOI to be ignored
           Product: Virtualization
           Version: unspecified
    Kernel Version: 5.17.9
          Hardware: Intel
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: kvm
          Assignee: virtualization_kvm@kernel-bugs.osdl.org
          Reporter: ercli@ucdavis.edu
        Regression: No

Created attachment 301071
  --> https://bugzilla.kernel.org/attachment.cgi?id=301071&action=edit
Guest hypervisor to reproduce this bug (xz compressed)

CPU model: 11th Gen Intel(R) Core(TM) i7-1185G7 @ 3.00GHz
Host kernel version: 5.17.9
Host kernel arch: x86_64
Guest: a micro-hypervisor (called XMHF), which runs Linux (64-bit Debian,
5.10.0-9-amd64)
QEMU command line: qemu-system-x86_64 -m 512M -smp 2 -cpu Haswell,vmx=yes
-enable-kvm -serial stdio -drive media=disk,file=c.img,index=1 -drive
media=disk,file=debian11x64.qcow2,index=2
The problem goes away if using -machine kernel_irqchip=off
This problem cannot be tested with -accel tcg , because the guest requires
nested virtualization

Files used to reproduce this bug:

debian11x64.qcow2 (3.3G) is uploaded at
https://drive.google.com/uc?id=1LtUwnzH8pDvjoBhJhxk5wIz9_UTlGaBA . It should be
equivalent to a freshly installed Debian 5.10.0-9-amd64 on QEMU. Its kaslr is
disabled for debugging convenience.

c.img (8M) is uploaded at
https://drive.google.com/uc?id=1g3c9KMAoh_Yvb9bzSuOBMG5L-2VX6twU . It is also
compressed as c.img.xz and uploaded with this bug. It is built from
https://github.com/lxylxy123456/uberxmhf/tree/ab7968ed8017f43978081862526636f75c80a3b7
.

Actual behavior:

After running the QEMU command above, the hypervisor (XMHF) will boot and then
chain load Debian as a guest OS. Debian starts to boot and stuck. In QEMU's
monitor, if I enter "info lapic", I see

...
ISR      253
IRR      48 236 253

Expected behavior:

When running the QEMU command above, the hypervisor should boot Debian, and
Debian should boot successfully. The VGA screen should show "debian login:".

The expected behavior can be achieved in a few ways:
1. Remove "-drive media=disk,file=c.img,index=1" from QEMU command line. This
will boot Debian directly (instead of booting XMHF and then boot Debian)
2. Add "-machine kernel_irqchip=off" to the QEMU command line
3. Apply the following patch to KVM and re-compile. This patch will let KVM
think that x2APIC virtualization is not available.

diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
index 3f430e218..29b412ae4 100644
--- a/arch/x86/kvm/vmx/capabilities.h
+++ b/arch/x86/kvm/vmx/capabilities.h
@@ -157,8 +157,7 @@ static inline bool cpu_has_vmx_rdtscp(void)

 static inline bool cpu_has_vmx_virtualize_x2apic_mode(void)
 {
-       return vmcs_config.cpu_based_2nd_exec_ctrl &
-               SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE;
+       return 0;
 }

 static inline bool cpu_has_vmx_vpid(void)

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