ae87f609cd
Use hypercall to emulate MSR read/write for the TDX platform. There are two viable approaches for doing MSRs in a TD guest: 1. Execute the RDMSR/WRMSR instructions like most VMs and bare metal do. Some will succeed, others will cause a #VE. All of those that cause a #VE will be handled with a TDCALL. 2. Use paravirt infrastructure. The paravirt hook has to keep a list of which MSRs would cause a #VE and use a TDCALL. All other MSRs execute RDMSR/WRMSR instructions directly. The second option can be ruled out because the list of MSRs was challenging to maintain. That leaves option #1 as the only viable solution for the minimal TDX support. Kernel relies on the exception fixup machinery to handle MSR access errors. #VE handler uses the same exception fixup code as #GP. It covers MSR accesses along with other types of fixups. For performance-critical MSR writes (like TSC_DEADLINE), future patches will replace the WRMSR/#VE sequence with the direct TDCALL. RDMSR and WRMSR specification details can be found in Guest-Host-Communication Interface (GHCI) for Intel Trust Domain Extensions (Intel TDX) specification, sec titled "TDG.VP. VMCALL<Instruction.RDMSR>" and "TDG.VP.VMCALL<Instruction.WRMSR>". Co-developed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com> 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> Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20220405232939.73860-10-kirill.shutemov@linux.intel.com |
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| core.c | ||
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