Sean Christopherson 946c522b60 KVM: nVMX: Sign extend displacements of VMX instr's mem operands ... The VMCS.EXIT_QUALIFCATION field reports the displacements of memory operands for various instructions, including VMX instructions, as a naturally sized unsigned value, but masks the value by the addr size, e.g. given a ModRM encoded as -0x28(%ebp), the -0x28 displacement is reported as 0xffffffd8 for a 32-bit address size. Despite some weird wording regarding sign extension, the SDM explicitly states that bits beyond the instructions address size are undefined: In all cases, bits of this field beyond the instruction’s address size are undefined. Failure to sign extend the displacement results in KVM incorrectly treating a negative displacement as a large positive displacement when the address size of the VMX instruction is smaller than KVM's native size, e.g. a 32-bit address size on a 64-bit KVM. The very original decoding, added by commit 064aea7747 ("KVM: nVMX: Decoding memory operands of VMX instructions"), sort of modeled sign extension by truncating the final virtual/linear address for a 32-bit address size. I.e. it messed up the effective address but made it work by adjusting the final address. When segmentation checks were added, the truncation logic was kept as-is and no sign extension logic was introduced. In other words, it kept calculating the wrong effective address while mostly generating the correct virtual/linear address. As the effective address is what's used in the segment limit checks, this results in KVM incorreclty injecting #GP/#SS faults due to non-existent segment violations when a nested VMM uses negative displacements with an address size smaller than KVM's native address size. Using the -0x28(%ebp) example, an EBP value of 0x1000 will result in KVM using 0x100000fd8 as the effective address when checking for a segment limit violation. This causes a 100% failure rate when running a 32-bit KVM build as L1 on top of a 64-bit KVM L0. Fixes: f9eb4af67c ("KVM: nVMX: VMX instructions: add checks for #GP/#SS exceptions") Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>		2019-02-20 22:48:22 +01:00
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capabilities.h
evmcs.c	x86/kvm/hyper-v: nested_enable_evmcs() sets vmcs_version incorrectly	2019-01-25 19:11:37 +01:00
evmcs.h
nested.c	KVM: nVMX: Sign extend displacements of VMX instr's mem operands	2019-02-20 22:48:22 +01:00
nested.h
ops.h
pmu_intel.c
vmcs.h	KVM: nVMX: Cache host_rsp on a per-VMCS basis	2019-02-12 13:12:22 +01:00
vmcs12.c
vmcs12.h
vmcs_shadow_fields.h
vmenter.S	KVM: VMX: Reorder clearing of registers in the vCPU-run assembly flow	2019-02-20 22:48:18 +01:00
vmx.c	KVM: VMX: Call vCPU-run asm sub-routine from C and remove clobbering	2019-02-20 22:48:18 +01:00
vmx.h	KVM: VMX: Pass "launched" directly to the vCPU-run asm blob	2019-02-12 13:12:24 +01:00