Re: [PATCHv2 13/29] x86/tdx: Add port I/O emulation

Thomas Gleixner
2022-02-01T23:01:26Z

On Mon, Jan 24 2022 at 18:01, Kirill A. Shutemov wrote:
> static bool intel_cc_platform_has(enum cc_attr attr)
> {
> + if (attr == CC_ATTR_GUEST_UNROLL_STRING_IO)
> + return true;
> +

switch (attr) perhaps as there are more coming, right?

> return false;
> }

> +/*
> + * Emulate I/O using hypercall.
> + *
> + * Assumes the IO instruction was using ax, which is enforced
> + * by the standard io.h macros.
> + *
> + * Return True on success or False on failure.
> + */
> +static bool tdx_handle_io(struct pt_regs *regs, u32 exit_qual)
> +{
> + struct tdx_hypercall_output out;
> + int size, port, ret;
> + u64 mask;
> + bool in;
> +
> + if (VE_IS_IO_STRING(exit_qual))
> + return false;
> +
> + in = VE_IS_IO_IN(exit_qual);
> + size = VE_GET_IO_SIZE(exit_qual);
> + port = VE_GET_PORT_NUM(exit_qual);
> + mask = GENMASK(BITS_PER_BYTE * size, 0);
> +
> + /*
> + * Emulate the I/O read/write via hypercall. More info about
> + * ABI can be found in TDX Guest-Host-Communication Interface
> + * (GHCI) sec titled "TDG.VP.VMCALL<Instruction.IO>".
> + */
> + ret = _tdx_hypercall(EXIT_REASON_IO_INSTRUCTION, size, !in, port,
> + in ? 0 : regs->ax, &out);
> + if (!in)
> + return !ret;
> +
> + regs->ax &= ~mask;
> + regs->ax |= ret ? UINT_MAX : out.r11 & mask;
> +
> + return !ret;
> +}
> +
> bool tdx_get_ve_info(struct ve_info *ve)
> {
> struct tdx_module_output out;
> @@ -333,6 +378,9 @@ static bool tdx_virt_exception_kernel(struct pt_regs *regs, struct ve_info *ve)
> if (!ret)
> pr_warn_once("MMIO failed\n");
> break;
> + case EXIT_REASON_IO_INSTRUCTION:
> + ret = tdx_handle_io(regs, ve->exit_qual);

return ...

Other than that LGTM.

Thanks,

tglx