On Fri, Feb 5, 2021 at 3:39 PM Kuppuswamy Sathyanarayanan <[email protected]> wrote: > > From: "Kirill A. Shutemov" <[email protected]> > > TDX has three classes of CPUID leaves: some CPUID leaves > are always handled by the CPU, others are handled by the TDX module, > and some others are handled by the VMM. Since the VMM cannot directly > intercept the instruction these are reflected with a #VE exception > to the guest, which then converts it into a TDCALL to the VMM, > or handled directly. > > The TDX module EAS has a full list of CPUID leaves which are handled > natively or by the TDX module in 16.2. Only unknown CPUIDs are handled by > the #VE method. In practice this typically only applies to the > hypervisor specific CPUIDs unknown to the native CPU. > > Therefore there is no risk of causing this in early CPUID code which > runs before the #VE handler is set up because it will never access > those exotic CPUID leaves. > > Signed-off-by: Kirill A. Shutemov <[email protected]> > Reviewed-by: Andi Kleen <[email protected]> > Signed-off-by: Kuppuswamy Sathyanarayanan > <[email protected]> > --- > arch/x86/kernel/tdx.c | 32 ++++++++++++++++++++++++++++++++ > 1 file changed, 32 insertions(+) > > diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c > index 5d961263601e..e98058c048b5 100644 > --- a/arch/x86/kernel/tdx.c > +++ b/arch/x86/kernel/tdx.c > @@ -172,6 +172,35 @@ static int tdx_write_msr_safe(unsigned int msr, unsigned > int low, > return ret || r10 ? -EIO : 0; > } > > +static void tdx_handle_cpuid(struct pt_regs *regs) > +{ > + register long r10 asm("r10") = TDVMCALL_STANDARD; > + register long r11 asm("r11") = EXIT_REASON_CPUID; > + register long r12 asm("r12") = regs->ax; > + register long r13 asm("r13") = regs->cx; > + register long r14 asm("r14"); > + register long r15 asm("r15"); > + register long rcx asm("rcx"); > + long ret; > + > + /* Allow to pass R10, R11, R12, R13, R14 and R15 down to the VMM */ > + rcx = BIT(10) | BIT(11) | BIT(12) | BIT(13) | BIT(14) | BIT(15); > + > + asm volatile(TDCALL > + : "=a"(ret), "=r"(r10), "=r"(r11), "=r"(r12), > "=r"(r13), > + "=r"(r14), "=r"(r15) > + : "a"(TDVMCALL), "r"(rcx), "r"(r10), "r"(r11), > "r"(r12), > + "r"(r13) > + : );
Some "+" constraints would make this simpler. But I think you should factor the TDCALL helper out into its own function.
