Re: [PATCH v8 0/5] Support x2APIC mode with TCG accelerator

[Bui Quang Minh]

On 9/26/23 23:06, Bui Quang Minh wrote:

> Version 8 changes,
> - Patch 2, 4:
>    + Rebase to master and resolve conflicts in these 2 patches

The conflicts when rebasing is due to the commit 9926cf34de5fa15da 
("target/i386: Allow elision of kvm_enable_x2apic()"). AFAIK, this 
commit adds kvm_enabled() before kvm_enable_x2apic() in the and (&&) 
expression so that when kvm_enabled() is known to be false at the 
compile time (CONFIG_KVM_IS_POSSIBLE is undefined), the compiler can 
omit the kvm_enable_x2apic() in the and expression.

In patch 2, I simply combine the change logic in patch 2 with logic in 
the commit 9926cf34de5fa15da.

In patch 4, the end result of version 8 is the same as version 7. I 
don't think we need to add the kvm_enabled() to make the expression become

        if (kvm_enabled() && kvm_irqchip_is_split() && !kvm_enable_x2apic())

Because when CONFIG_KVM_IS_POSSIBLE is undefined, kvm_irqchip_is_split() 
is known to be false at the compile time too so just keep the expression as

        if (kvm_irqchip_is_split() && !kvm_enable_x2apic())

is enough.

> git range-diff feat/tcg-x2apic-v7~5..feat/tcg-x2apic-v7 
feat/tcg-x2apic-v8~5..feat/tcg-x2apic-v8

1:  c1d197a230 = 1:  f6e3918e0f i386/tcg: implement x2APIC registers MSR 
access
2:  dd96cb0238 ! 2:  54d44a15b6 apic: add support for x2APIC mode
    @@ Commit message

      ## hw/i386/x86.c ##
     @@ hw/i386/x86.c: void x86_cpus_init(X86MachineState *x86ms, int 
default_cpu_version)
    -      * Can we support APIC ID 255 or higher?
    -      *
    -      * Under Xen: yes.
    --     * With userspace emulated lapic: no
    -+     * With userspace emulated lapic: checked later in 
apic_common_set_id.
    -      * With KVM's in-kernel lapic: only if X2APIC API is enabled.
    +      * both in-kernel lapic and X2APIC userspace API.
           */
    -     if (x86ms->apic_id_limit > 255 && !xen_enabled() &&
    +     if (x86ms->apic_id_limit > 255 && kvm_enabled() &&
     -        (!kvm_irqchip_in_kernel() || !kvm_enable_x2apic())) {
     +        kvm_irqchip_in_kernel() && !kvm_enable_x2apic()) {
              error_report("current -smp configuration requires kernel "
3:  31a5c555a6 = 3:  eb080d1e2c apic, i386/tcg: add x2apic transitions
4:  d78b5c43b4 ! 4:  59f028f119 intel_iommu: allow Extended Interrupt 
Mode when using userspace APIC
    @@ hw/i386/intel_iommu.c: static bool 
vtd_decide_config(IntelIOMMUState *s, Error *
     -            error_setg(errp, "eim=on requires 
accel=kvm,kernel-irqchip=split");
     -            return false;
     -        }
    --        if (!kvm_enable_x2apic()) {
    +-        if (kvm_enabled() && !kvm_enable_x2apic()) {
     +        if (kvm_irqchip_is_split() && !kvm_enable_x2apic()) {
                  error_setg(errp, "eim=on requires support on the KVM 
side"
                                   "(X2APIC_API, first shipped in v4.7)");
5:  51f558035d = 5:  bc95c3cb60 amd_iommu: report x2APIC support to the 
operating system

As the change is minor and does not change the main logic, I keep the 
Reviewed-by and Acked-by tags.

Thank you,
Quang Minh.