Messages in this thread | | | Date | Fri, 5 Nov 2021 21:23:55 +0000 | From | Sean Christopherson <> | Subject | Re: [PATCH v7 05/10] x86/tdx: Handle port I/O |
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On Tue, Oct 05, 2021, Kuppuswamy Sathyanarayanan wrote: > diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c > index 4cbffcb737d9..cd0fb5d14ad7 100644 > --- a/arch/x86/kernel/tdx.c > +++ b/arch/x86/kernel/tdx.c > @@ -175,6 +175,38 @@ static u64 tdx_handle_cpuid(struct pt_regs *regs) > return ret; > } > > +/* > + * tdx_handle_early_io() cannot be re-used in #VE handler for handling > + * I/O because the way of handling string I/O is different between > + * normal and early I/O case. Also, once trace support is enabled, > + * tdx_handle_io() will be extended to use trace calls which is also > + * not valid for early I/O cases. > + */ > +static void tdx_handle_io(struct pt_regs *regs, u32 exit_qual) > +{ > + struct tdx_hypercall_output outh;
Same comments as patch 04.
> + int out, size, port, ret; > + bool string; > + u64 mask; > + > + string = VE_IS_IO_STRING(exit_qual); > + > + /* I/O strings ops are unrolled at build time. */ > + BUG_ON(string);
And here as well.
> + > + out = VE_IS_IO_OUT(exit_qual); > + size = VE_GET_IO_SIZE(exit_qual); > + port = VE_GET_PORT_NUM(exit_qual); > + mask = GENMASK(8 * size, 0);
And here.
> + > + ret = _tdx_hypercall(EXIT_REASON_IO_INSTRUCTION, size, out, port, > + regs->ax, &outh);
This one too.
> + if (!out) {
This needs to check "ret". In general, why is this continuing on if I/O fails? If I/O fails, the kernel done messed up and some downstream driver is going to be real unhappy. At a minimum, it should WARN.
On a related topic, the GHCB says:
TDG.VP.VMCALL_INVALID_OPERAND 0x80000000 00000000 Invalid-IO-Port access
The "Invalid-IO-Port access" in particular is poorly worded as it implies the VMM is allowed to deny access to ports, but AFAIK that's not the intention. A better phrasing would be something like "Reserved value in input GPR".
The GHCI should probably also state that bits 63:16 of R14 (port) are reserved.
> + regs->ax &= ~mask; > + regs->ax |= (ret ? UINT_MAX : outh.r11) & mask; > + } > +}
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