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    Subject[PATCH 5.16 0792/1039] KVM: x86: Handle 32-bit wrap of EIP for EMULTYPE_SKIP with flat code seg
    Date
    From: Sean Christopherson <seanjc@google.com>

    [ Upstream commit 5e854864ee4384736f27a986633bae21731a4e4e ]

    Truncate the new EIP to a 32-bit value when handling EMULTYPE_SKIP as the
    decode phase does not truncate _eip. Wrapping the 32-bit boundary is
    legal if and only if CS is a flat code segment, but that check is
    implicitly handled in the form of limit checks in the decode phase.

    Opportunstically prepare for a future fix by storing the result of any
    truncation in "eip" instead of "_eip".

    Fixes: 1957aa63be53 ("KVM: VMX: Handle single-step #DB for EMULTYPE_SKIP on EPT misconfig")
    Signed-off-by: Sean Christopherson <seanjc@google.com>
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
    Message-Id: <093eabb1eab2965201c9b018373baf26ff256d85.1635842679.git.houwenlong93@linux.alibaba.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/x86/kvm/x86.c | 7 ++++++-
    1 file changed, 6 insertions(+), 1 deletion(-)

    diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    index bb87f43cdc78c..5d5a8e75edcb7 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -8134,7 +8134,12 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
    * updating interruptibility state and injecting single-step #DBs.
    */
    if (emulation_type & EMULTYPE_SKIP) {
    - kvm_rip_write(vcpu, ctxt->_eip);
    + if (ctxt->mode != X86EMUL_MODE_PROT64)
    + ctxt->eip = (u32)ctxt->_eip;
    + else
    + ctxt->eip = ctxt->_eip;
    +
    + kvm_rip_write(vcpu, ctxt->eip);
    if (ctxt->eflags & X86_EFLAGS_RF)
    kvm_set_rflags(vcpu, ctxt->eflags & ~X86_EFLAGS_RF);
    return 1;
    --
    2.34.1


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