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virtualbox: VBoxVMI register read and write - #306
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read_registers and write_registers go through the VBoxVMI REGS_READ and REGS_WRITE commands: the full X86Registers set of one vCPU, MSRs included, in one round trip, served by the vCPU's EMT between two of its instructions (a consistent snapshot, an atomic write, also on a running VM). A write is all or nothing: a value the CPU would not load (e.g. RFLAGS bit 1 clear) fails it without writing anything. efer and msr_efer are both EFER and must be equal in a write. rs-vboxvmi is bumped to 5452496 for the new commands. The register tests run under both methods: the invalid RFLAGS check goes through the driver instead of VBoxManage setregisters (which needs the MachineDebugger patch), registers_unchanged_while_paused checks that an unknown vCPU is an error, and the new virtualbox_write_registers_survive_resume checks that written registers are still there after the guest ran. The driver and test docs list registers as supported by VBoxVMI, with filters running every VBoxVMI test once, for 1 and 2 vCPUs. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
VirtualBox has one EFER register, which X86Registers::efer and msr_efer both are. A register write giving them different values now fails with the shared EferMismatch error before anything is written, also with the MachineDebugger method, which wrote both to the same DBGF register and let the last one win. Documented on the driver page and the efer field. virtualbox_write_registers_survive_resume waits until a cold-booted guest has set SYSENTER_EIP on the vCPU it writes, and restores only the two MSRs it changed: the other registers moved on while the guest ran. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Closes #284.
read_registers/write_registers: one round trip each, via rs-vboxvmi5452496. Writes are all or nothing; values the CPU would refuse returnInvalidRegisters.efer != msr_eferwith a sharedEferMismatcherror (VirtualBox has one EFER register); documented on the driver page andX86Registers::efer.virtualbox_write_registers_survive_resume(SYSENTER MSRs written while paused survive 1 s of guest execution; restores only those MSRs afterwards).Server: Wenzel/virtualbox#7 (merged into
vmi/vboxvmi).Verified live with 1 and 2 vCPUs: full VBoxVMI suite (init, pause, vCPU, registers, page walk + banner, register writes, survive_resume, reads) and MachineDebugger register tests. fmt, clippy
-D warnings(virtualbox-api, virtualbox-vmi, both with --tests),virtualbox_errorspass.