The address translation logic in get_physical_address() will currently truncate physical addresses to 32 bits unless long mode is enabled. This is incorrect when using physical address extensions (PAE) outside of long mode, with the result that a 32-bit operating system using PAE to access memory above 4G will experience undefined behaviour. Instead, truncation must be applied to the linear address. Because this truncation is diffent between 32- and 64-bit modes, the series opts to split 32- and 64-bit modes to separate MMU indices, which is the simplest way to ensure that, for example, a kernel that runs both 32-bit and 64-bit programs looks up the correct address in the (64-bit) page tables.
Furthermore, when inspecting the code I noticed that the A20 mask is applied incorrectly when NPT is active. The mask should not be applied to the addresses that are looked up in the NPT, only to the physical addresses. Obviously no hypervisor is going to leave A20 masking on, but the code actually becomes simpler so let's do it. Patches 1 and 2 fix cases in which the addresses must be masked, or overflow is otherwise invalid, for MMU_PHYS_IDX accesses. Patches 3 and 4 introduce separate MMU indexes for 32- and 64-bit accesses. Patch 5 fixes the bug, by limiting the masking to the 32-bit MMU indexes. Patches 6 and 7 further clean up the MMU functions to centralize application of the A20 mask and fix bugs in the process. Tested with kvm-unit-tests SVM tests and with an old 32-bit Debian image. Paolo Bonzini (7): target/i386: mask high bits of CR3 in 32-bit mode target/i386: check validity of VMCB addresses target/i386: introduce function to query MMU indices target/i386: use separate MMU indexes for 32-bit accesses target/i386: Fix physical address truncation target/i386: remove unnecessary/wrong application of the A20 mask target/i386: leave the A20 bit set in the final NPT walk target/i386/cpu.h | 46 +++++++++++++++++++----- target/i386/cpu.c | 9 +++-- target/i386/tcg/sysemu/excp_helper.c | 52 +++++++++++++--------------- target/i386/tcg/sysemu/misc_helper.c | 3 ++ target/i386/tcg/sysemu/svm_helper.c | 27 +++++++++++---- 5 files changed, 92 insertions(+), 45 deletions(-) -- 2.43.0
