On 27/08/21 05:12, Zixuan Wang wrote:
+ * + * This is because KVM-Unit-Tests reuses UEFI #VC handler that requires UEFI + * code and data segments to run. The UEFI #VC handler crashes the guest VM if + * these segments are not available. So we need to copy these two UEFI segments + * into KVM-Unit-Tests GDT. + * + * UEFI uses 0x30 as code segment and 0x38 as data segment. Fortunately, these + * segments can be safely overridden in KVM-Unit-Tests as they are used as + * protected mode and real mode segments (see x86/efi/efistart64.S for more + * details), which are not used in EFI set up process.
Is 0x30/0x38 the same as kvm-unit-tests's 0x08/0x10? Can kvm-unit-tests simply change its ring-0 64-bit CS/DS to 0x30 and 0x38 instead of 0x08 and 0x10? I can help with that too, since there would be some more shuffling to keep similar descriptors together: * 0x00 NULL descriptor NULL descriptor * 0x08 intr_alt_stack TSS ring-0 code segment (32-bit) * 0x10 (0x13) **unused** ring-3 code segment (64-bit) * 0x18 ring-0 code segment (P=0) ring-0 code segment (64-bit, P=0) * 0x20 ring-0 code segment (16-bit) same * 0x28 ring-0 data segment (16-bit) same * 0x30 ring-0 code segment (32-bit) ring-0 code segment (64-bit) * 0x38 ring-0 data segment (32-bit) ring-0 data segment (32/64-bit) * 0x40 (0x43) ring-3 code segment (32-bit) same * 0x48 (0x4b) ring-3 data segment (32-bit) ring-3 data segment (32/64-bit) * 0x50-0x78 free to use for test cases same or: old new ---- ---- 0x00 0x00 0x20 0x08 0x48 0x10 0x18 0x18 0x28 0x20 0x30 0x28 0x08 0x30 0x10 0x38 0x38 0x40 0x40 0x48 Thanks, Paolo
