Messages in this thread | | | Date | Fri, 24 Jun 2022 18:41:38 +0200 | From | Paolo Bonzini <> | Subject | Re: [PATCH v6 15/17] KVM: SVM: Use target APIC ID to complete x2AVIC IRQs when possible |
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On 5/19/22 12:27, Suravee Suthikulpanit wrote: > + * If the x2APIC logical ID sub-field (i.e. icrh[15:0]) contains zero > + * or more than 1 bits, we cannot match just one vcpu to kick for > + * fast path. > + */ > + if (!first || (first != last)) > + return -EINVAL; > + > + apic = first - 1; > + if ((apic < 0) || (apic > 15) || (cluster >= 0xfffff)) > + return -EINVAL;
Neither of these is possible: first == 0 has been cheked above, and ffs(icrh & 0xffff) cannot exceed 15. Likewise, cluster is actually limited to 16 bits, not 20.
Plus, C is not Pascal so no parentheses. :)
Putting everything together, it can be simplified to this:
+ int cluster = (icrh & 0xffff0000) >> 16; + int apic = ffs(icrh & 0xffff) - 1; + + /* + * If the x2APIC logical ID sub-field (i.e. icrh[15:0]) + * contains anything but a single bit, we cannot use the + * fast path, because it is limited to a single vCPU. + */ + if (apic < 0 || icrh != (1 << apic)) + return -EINVAL; + + l1_physical_id = (cluster << 4) + apic;
> + apic_id = (cluster << 4) + apic;
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