> -----Original Message----- > From: Michael S. Tsirkin [mailto:m...@redhat.com] > Sent: Wednesday, March 26, 2014 6:31 PM > To: Bug 1297651 > Cc: qemu-devel@nongnu.org; ehabk...@redhat.com; ler...@redhat.com; Hu, > Robert > Subject: Re: [Bug 1297651] [NEW] KVM create a win7 guest with Qemu, it boots > up fail > > On Wed, Mar 26, 2014 at 06:45:10AM -0000, Robert Hu wrote: > > Public bug reported: > > > > Environment: > > ------------ > > Host OS (ia32/ia32e/IA64):ia32e > > Guest OS (ia32/ia32e/IA64):ia32e > > Guest OS Type (Linux/Windows):Windows > > kvm.git Commit:94b3ffcd41a90d2cb0b32ca23aa58a01111d5dc0 > > qemu-kvm Commit:839a5547574e57cce62f49bfc50fe1f04b00589a > > Host Kernel Version:3.14.0-rc3 > > Hardware:Romley_EP, Ivytown_EP, HSW_EP > > > > > > Bug detailed description: > > -------------------------- > > when create a win7 guest, the guest boot up fail. > > > > note: > > 1. when create win2000, winxp, win2k3, win2k8, guest, the guest boot up > > fail. > > 2. when create win8, win8.1, win2012 guest, the guest boot up fine. > > > > > > Reproduce steps: > > ---------------- > > 1.create guest > > qemu-system-x86_64 -enable-kvm -m 1024 -smp 2 -net none -hda > /root/win7.qcow > > > > > > Current result: > > ---------------- > > win7 guest boot up fail > > > > Expected result: > > ---------------- > > win7 guest boot up fine > > > > Basic root-causing log: > > ---------------------- > > > > This should be a qemu bug > > kvm + qemu = result > > 94b3ffcd + 839a5547 = bad > > 94b3ffcd + 3a87f8b6 = good > > > > the first bad commit is: > > commit 9bcc80cd71892df42605e0c097d85c0237ff45d1 > > Author: Laszlo Ersek <ler...@redhat.com> > > Thanks for the excellent bug report! > > > > > Date: Mon Mar 17 17:05:16 2014 +0100 > > > > i386/acpi-build: allow more than 255 elements in CPON > > > > The build_ssdt() function builds a number of AML objects that are > > related > > to CPU hotplug, and whose IDs form a contiguous sequence of APIC IDs. > > (APIC IDs are in fact discontiguous, but this is the traditional > > interface: build a contiguous sequence from zero up that covers all > > possible APIC IDs.) These objects are: > > > > - a Processor() object for each VCPU, > > - a NTFY method, with one branch for each VCPU, > > - a CPON package with one element (hotplug status byte) for each VCPU. > > > > The build_ssdt() function currently limits the *count* of processor > > objects, and NTFY branches, and CPON elements, in 0xFF (see the > assignment > > to "acpi_cpus"). This allows for an inclusive APIC ID range of [0..254]. > > This is incorrect, because the highest APIC ID that we otherwise allow a > > VCPU to take is 255. > > > > In order to extend the maximum count to 256, and the traversed APIC ID > > range correspondingly to [0..255]: > > - the Processor() objects need no change, > > - the NTFY method also needs no change, > > - the CPON package must be updated, because it is defined with a > > DefPackage, and the number of elements in such a package can be at > most > > 255. We pick a DefVarPackage instead. > > > > We replace the Op byte, and the encoding of the number of elements. > > Compare: > > > > DefPackage := PackageOp PkgLength NumElements > PackageElementList > > DefVarPackage := VarPackageOp PkgLength VarNumElements > PackageElementList > > > > PackageOp := 0x12 > > VarPackageOp := 0x13 > > > I think I know what's going on here: the specification says: > > The ASL compiler can emit two different AML opcodes for a Package > declaration, either PackageOp or VarPackageOp. For small, fixed-length > packages, the PackageOp is used and this > > opcode is compatible with ACPI 1.0. A VarPackageOp will be emitted if > any of the following conditions are true: > • > The NumElements argument is a TermArg that can only be resolved at > runtime. > • > At compile time, NumElements resolves to a constant that is larger than > 255. > • > The PackageList contains more than 255 initializer elements. > > > So we clearly violate this rule. > > > > > > NumElements := ByteData > > VarNumElements := TermArg => Integer > > > > The build_append_int() function implements precisely the following > TermArg > > encodings (a subset of what the ACPI spec describes): > > > > TermArg := DataObject > > DataObject := ComputationalData > > ComputationalData := ConstObj | ByteConst | WordConst | > DWordConst > > directly encoded in the function, with build_append_byte(): > > ConstObj := ZeroOp | OneOp > > ZeroOp := 0x00 > > OneOp := 0x01 > > > > call to build_append_value(..., 1): > > ByteConst := BytePrefix ByteData > > BytePrefix := 0x0A > > ByteData := 0x00 - 0xFF > > > > call to build_append_value(..., 2): > > WordConst := WordPrefix WordData > > WordPrefix := 0x0B > > WordData := ByteData[0:7] ByteData[8:15] > > > > call to build_append_value(..., 4): > > DWordConst := DWordPrefix DWordData > > DWordPrefix := 0x0C > > DWordData := WordData[0:15] WordData[16:31] > > > > Signed-off-by: Laszlo Ersek <ler...@redhat.com> > > Reviewed-by: Michael S. Tsirkin <m...@redhat.com> > > Signed-off-by: Michael S. Tsirkin <m...@redhat.com> > > > > ** Affects: qemu > > Importance: Undecided > > Status: New > > > > The following seems to fix the issue - still testing. Can you confirm please? > However the question we should ask is whether > it's a good idea to allow hotplug ID values that might > make guests fail to boot. > > How about limiting ACPI_CPU_HOTPLUG_ID_LIMIT to 255? > > We never allowed > 255 in the past, is it worth the > maintainance headaches? > > > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c > index f1054dd..7597517 100644 > --- a/hw/i386/acpi-build.c > +++ b/hw/i386/acpi-build.c > @@ -1055,9 +1055,21 @@ build_ssdt(GArray *table_data, GArray *linker, > > { > GArray *package = build_alloc_array(); > - uint8_t op = 0x13; /* VarPackageOp */ > + uint8_t op; > + > + /* > + * Note: The ability to create variable-sized packages was first > introduced in ACPI 2.0. ACPI 1.0 only > + * allowed fixed-size packages with up to 255 elements. > + * Windows guests up to win2k8 fail when VarPackageOp is used. > + */ > + if (acpi_cpus <= 255) { > + op = 0x12; /* PackageOp */ > + build_append_byte(package, acpi_cpus); /* NumElements > */ > + } else { > + op = 0x13; /* VarPackageOp */ > + build_append_int(package, acpi_cpus); /* VarNumElements > */ > + } > > - build_append_int(package, acpi_cpus); /* VarNumElements */ > for (i = 0; i < acpi_cpus; i++) { > uint8_t b = test_bit(i, cpu->found_cpus) ? 0x01 : 0x00; > build_append_byte(package, b); Patch to qemu(839a5547574e57), guest can boot fine.