x86/insn-eval: Introduce insn_decode_mmio()
In preparation for sharing MMIO instruction decode between SEV-ES and TDX, factor out the common decode into a new insn_decode_mmio() helper. For regular virtual machine, MMIO is handled by the VMM and KVM emulates instructions that caused MMIO. But, this model doesn't work for a secure VMs (like SEV or TDX) as VMM doesn't have access to the guest memory and register state. So, for TDX or SEV VMM needs assistance in handling MMIO. It induces exception in the guest. Guest has to decode the instruction and handle it on its own. The code is based on the current SEV MMIO implementation. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Andi Kleen <ak@linux.intel.com> Reviewed-by: Tony Luck <tony.luck@intel.com> Tested-by: Joerg Roedel <jroedel@suse.de> Acked-by: Tom Lendacky <thomas.lendacky@amd.com> Link: https://lkml.kernel.org/r/20211130184933.31005-4-kirill.shutemov@linux.intel.com
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