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    SubjectRe: [PATCH v2 3/3] paravirt: rename paravirt_enabled to paravirt_legacy
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    On 02/06/2016 03:59 AM, Luis R. Rodriguez wrote:
    > The enumeration of legacy crap by ACPI boot flags seems to provide enough
    > details to suit our needs if we really wanted to zero down on the specifics of
    > what paravirt_legacy() means, there are these flags:
    >
    > /* Masks for FADT IA-PC Boot Architecture Flags (boot_flags) [Vx]=Introduced in this FADT revision */
    > #define ACPI_FADT_LEGACY_DEVICES (1) /* 00: [V2] System has LPC or ISA bus devices */
    > #define ACPI_FADT_8042 (1<<1) /* 01: [V3] System has an 8042 controller on port 60/64 */
    > #define ACPI_FADT_NO_VGA (1<<2) /* 02: [V4] It is not safe to probe for VGA hardware */
    > #define ACPI_FADT_NO_MSI (1<<3) /* 03: [V4] Message Signaled Interrupts (MSI) must not be enabled */
    > #define ACPI_FADT_NO_ASPM (1<<4) /* 04: [V4] PCIe ASPM control must not be enabled */
    > #define ACPI_FADT_NO_CMOS_RTC (1<<5) /* 05: [V5] No CMOS real-time clock present */
    >
    > I checked and I didn't see qemu using any of the ACPI boot flags,
    > but I suspected qemu instances must use a series of legacy crap.
    > Likewise for KVM.
    >
    > coreboot defines legacy free when you don't have any of the above flags set:
    > #define ACPI_FADT_LEGACY_FREE 0x00 /* No legacy devices (including 8042) *
    >
    > Would it be sufficient to just stick to "pv legacy" equivalent
    > of requiring just ACPI_FADT_LEGACY_DEVICES and ACPI_FADT_8042 ?

    I believe unprivileged PV guests may be compiled without CONFIG_ACPI if
    you are talking about requiring (or manually setting) these flags.

    -boris

    >
    > I should point out It turns out ACPI_FADT_NO_CMOS_RTC matches lguest's and it
    > seems that's the only reason we have that RTC PV flag and the features pv
    > field... with the linker table + x86 subarch use it should be relatively simple
    > to remove paravirt_has_feature() paravirt_has() and PV_SUPPORTED_RTC. lguest
    > would just be the only subarch that opts out.
    >
    > Luis

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