From: Yuan Yao <yuan.yao@xxxxxxxxx> This RFC series introduces the basic framework and a common implementation on x86 to handle encrypted guest memory reading/writing, to support QEMU's built-in guest debugging features, like the monitor command xp and gdbstub. The encrypted guest which its memory and/or register context is encrypted by vendor specific technology(AMD SEV/INTEL TDX), is able to resist the attack from malicious VMM or other privileged components in host side, however, this ability also breaks down the QEMU's built-in guest debugging features, because it prohibits the direct guest memory accessing (memcpy() with HVA) from QEMU which is the base of these debugging features. The framework part based on the previous patche set from AMD[1] and some discussion result in community[2]. The main idea is, introduce some new debug interfaces to handle the encrypted guest physical memory accessing, also introduce new interfaces in MemoryRegion to handle the actual accessing there with KVM, don't bother the exist memory access logic or callbacks as far as possible. [1] https://lore.kernel.org/qemu-devel/ cover.1605316268.git.ashish.kalra@xxxxxxx/ [2] https://lore.kernel.org/qemu-devel/ 20200922201124.GA6606@ashkalra_ubuntu_server/ - The difference part in this patch series: - We introduce another new vm level ioctl focus on the encrypted guest memory accessing: KVM_MEMORY_ENCRYPT_{READ,WRITE}_MEMORY struct kvm_rw_memory rw; rw.addr = gpa_OR_hva; rw.buf = (__u64)src; rw.len = len; kvm_vm_ioctl(kvm_state, KVM_MEMORY_ENCRYPT_{READ,WRITE}_MEMORY, &rw); This new ioctl has more neutral and general name for its purpose, the debugging support of AMD SEV and INTEL TDX can be covered by a unify QEMU implementation on x86 with this ioctl. Although only INTEL TD guest is supported in this series, AMD SEV could be also supported with implementation of this ioctl in KVM, plus small modifications in QEMU to enable the unify part. - The MemoryRegion interface introduced by AMD before now has addtional GPA parameter(only HVA before). This is for INTEL TDX which uses GPA to do guest memory accessing. This change won't impact AMD SEV which is using HVA to access the guest memory. - New APIs in QEMU: - Physical memory accessing: - cpu_physical_memory_rw_debug(). - cpu_physical_memory_read_debug(). - cpu_physical_memory_write_debug(). - x86_ldl_phys_debug(). - x86_ldq_phys_debug(). - Access from address_space: - address_space_read_debug(). - address_space_write_rom_debug(). - Virtual memory accessing and page table walking: - cpu_memory_rw_debug(). - x86_cpu_get_phys_page_attrs_encrypted_debug(). - New intrfaces in QEMU: - MemoryDebugOps *physical_memory_debug_op - For normal guest: Just call the old exist memory RW functions. - For encrypted guest: Forward the request to MemoryRegion->ram_debug_ops - MemoryRegionRAMReadWriteOps MemoryRegion::*ram_debug_ops - For normal guest: NULL and nobody use it. - For encrypted guest: Forward the request to common/vendor specific implementation. - The relationship diagram of the APIs and interfaces: +---------------------------------------------+ |x86_cpu_get_phys_page_attrs_encrypted_debug()| +----------------------------------+----------+ | +---------------------------------+ | |cpu_physical_memory_rw_debug() | | |cpu_physical_memory_read_debug() | | |cpu_physical_memory_write_debug()| | +----------------------+----------+ | | | +---------------------+ | +---------v----------+ |cpu_memory_rw_debug()| | |x86_ldl_phys_debug()| +-------------------+-+ | |x86_ldq_phys_debug()| | | +-------+------------+ | | | | | | +--------------------v---------v----------------v------------+ | MemoryDebugOps *physical_memory_debug_op | +----------------------+--------------------------+----------+ | | |Encrypted guest |Normal guest | | +--------------------v-----------------------+ | |address_space_encrypted_memory_read_debug() | | |address_space_encrypted_rom_write_debug() | | +--------------------+-----------------------+ | | | | +---------------v----------+ | |address_space_read() | | |address_space_write_rom() | | +--------------------------+ | +----------------v----------------+ | address_space_read_debug() | | address_space_write_rom_debug() | +----------------+----------------+ | | | +----------------v----------------+ | MemoryRegionRAMReadWriteOps | | MemoryRegion::*ram_debug_ops | +--------+--------------+---------+ | | | |Normal guest | | Encrypted guest| +---v-------------------+ | | NULL(nobody using it) | | +-----------------------+ | +---------v----------------------------+ | kvm_encrypted_guest_read_memory() | | kvm_encrypted_guest_write_memory() | +--------------------------------------+ Ashish Kalra (2): Introduce new MemoryDebugOps which hook into guest virtual and physical memory debug interfaces such as cpu_memory_rw_debug, to allow vendor specific assist/hooks for debugging and delegating accessing the guest memory. This is required for example in case of AMD SEV platform where the guest memory is encrypted and a SEV specific debug assist/hook will be required to access the guest memory. Add new address_space_read and address_space_write debug helper interfaces which can be invoked by vendor specific guest memory debug assist/hooks to do guest RAM memory accesses using the added MemoryRegion callbacks. Brijesh Singh (2): Extend the MemTxAttrs to include a 'debug' flag. The flag can be used as general indicator that operation was triggered by the debugger. Currently, guest memory access for debugging purposes is performed using memcpy(). Extend the 'struct MemoryRegion' to include new callbacks that can be used to override the use of memcpy() with something else. Yuan Yao (6): Introduce new interface KVMState::set_mr_debug_ops and its wrapper Implements the common MemoryRegion::ram_debug_ops for encrypted guests Set the RAM's MemoryRegion::debug_ops for INTEL TD guests Introduce debug version of physical memory read/write API Change the monitor and other commands and gdbstub to use the debug API Introduce new CPUClass::get_phys_page_attrs_debug implementation for encrypted guests accel/kvm/kvm-all.c | 17 +++++ accel/stubs/kvm-stub.c | 11 +++ dump/dump.c | 2 +- gdbstub.c | 4 +- hw/i386/pc.c | 4 + include/exec/cpu-common.h | 14 ++++ include/exec/memattrs.h | 4 + include/exec/memory.h | 54 +++++++++++++ include/sysemu/kvm.h | 5 ++ include/sysemu/tdx.h | 3 + monitor/misc.c | 12 ++- softmmu/cpus.c | 2 +- softmmu/physmem.c | 154 +++++++++++++++++++++++++++++++++++++- target/i386/cpu.h | 4 + target/i386/helper.c | 64 +++++++++++++--- target/i386/kvm/kvm.c | 68 +++++++++++++++++ target/i386/kvm/tdx.c | 21 ++++++ target/i386/monitor.c | 52 ++++++------- 18 files changed, 447 insertions(+), 48 deletions(-) -- 2.20.1
