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[BUG] PVH ACPI XSDT table construction

  • To: "xen-devel" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: Daniel Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
  • Date: Tue, 26 May 2020 13:13:19 -0400
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  • Delivery-date: Tue, 26 May 2020 17:13:47 +0000
  • Importance: Medium
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>


I was reviewing the ACPI construction for PVH and discovered what I believe is a flaw in the logic for selecting the XSDT tables. The current logic is,

static bool __init pvh_acpi_xsdt_table_allowed(const char *sig,
                                               unsigned long address,
                                               unsigned long size)
     * DSDT and FACS are pointed to from FADT and thus don't belong
     * in XSDT.
    return (pvh_acpi_table_allowed(sig, address, size) &&
            strncmp(sig, ACPI_SIG_DSDT, ACPI_NAME_SIZE) &&
            strncmp(sig, ACPI_SIG_FACS, ACPI_NAME_SIZE));

Unless I am mistaken, the boolean logic in the return statement will always return false resulting in an empty XSDT table. I believe based on the comment what was intended here was,

    return (pvh_acpi_table_allowed(sig, address, size) &&
            !(strncmp(sig, ACPI_SIG_DSDT, ACPI_NAME_SIZE) ||
              strncmp(sig, ACPI_SIG_FACS, ACPI_NAME_SIZE)));


Daniel P. Smith
Apertus Solutions, LLC



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