From 32e72854fa5fef6bc72e27c54f31897db9092acb Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Wed, 6 Apr 2022 02:29:27 +0300 Subject: [PATCH] x86/tdx: Port I/O: Add early boot support TDX guests cannot do port I/O directly. The TDX module triggers a #VE exception to let the guest kernel emulate port I/O by converting them into TDCALLs to call the host. But before IDT handlers are set up, port I/O cannot be emulated using normal kernel #VE handlers. To support the #VE-based emulation during this boot window, add a minimal early #VE handler support in early exception handlers. This is similar to what AMD SEV does. This is mainly to support earlyprintk's serial driver, as well as potentially the VGA driver. The early handler only supports I/O-related #VE exceptions. Unhandled or failed exceptions will be handled via early_fixup_exceptions() (like normal exception failures). At runtime I/O-related #VE exceptions (along with other types) handled by virt_exception_kernel(). Signed-off-by: Andi Kleen Signed-off-by: Kuppuswamy Sathyanarayanan Signed-off-by: Kirill A. Shutemov Signed-off-by: Dave Hansen Reviewed-by: Dan Williams Reviewed-by: Thomas Gleixner Reviewed-by: Dave Hansen Link: https://lkml.kernel.org/r/20220405232939.73860-19-kirill.shutemov@linux.intel.com --- arch/x86/coco/tdx/tdx.c | 16 ++++++++++++++++ arch/x86/include/asm/tdx.h | 4 ++++ arch/x86/kernel/head64.c | 3 +++ 3 files changed, 23 insertions(+) diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c index e47e2ed..cc14b7c 100644 --- a/arch/x86/coco/tdx/tdx.c +++ b/arch/x86/coco/tdx/tdx.c @@ -418,6 +418,22 @@ static bool handle_io(struct pt_regs *regs, u32 exit_qual) return handle_out(regs, size, port); } +/* + * Early #VE exception handler. Only handles a subset of port I/O. + * Intended only for earlyprintk. If failed, return false. + */ +__init bool tdx_early_handle_ve(struct pt_regs *regs) +{ + struct ve_info ve; + + tdx_get_ve_info(&ve); + + if (ve.exit_reason != EXIT_REASON_IO_INSTRUCTION) + return false; + + return handle_io(regs, ve.exit_qual); +} + void tdx_get_ve_info(struct ve_info *ve) { struct tdx_module_output out; diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h index 7944fd1..9ffd0d2e 100644 --- a/arch/x86/include/asm/tdx.h +++ b/arch/x86/include/asm/tdx.h @@ -65,11 +65,15 @@ bool tdx_handle_virt_exception(struct pt_regs *regs, struct ve_info *ve); void tdx_safe_halt(void); +bool tdx_early_handle_ve(struct pt_regs *regs); + #else static inline void tdx_early_init(void) { }; static inline void tdx_safe_halt(void) { }; +static inline bool tdx_early_handle_ve(struct pt_regs *regs) { return false; } + #endif /* CONFIG_INTEL_TDX_GUEST */ #endif /* !__ASSEMBLY__ */ diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index 6dff50c..ecbf50e 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -417,6 +417,9 @@ void __init do_early_exception(struct pt_regs *regs, int trapnr) trapnr == X86_TRAP_VC && handle_vc_boot_ghcb(regs)) return; + if (trapnr == X86_TRAP_VE && tdx_early_handle_ve(regs)) + return; + early_fixup_exception(regs, trapnr); } -- 2.7.4