From 7b804135d4d1f0a2b9dda69c6303d3f2dcbe9d37 Mon Sep 17 00:00:00 2001 From: Kai Huang Date: Tue, 15 Aug 2023 23:02:05 +1200 Subject: x86/virt/tdx: Make TDX_MODULE_CALL handle SEAMCALL #UD and #GP SEAMCALL instruction causes #UD if the CPU isn't in VMX operation. Currently the TDX_MODULE_CALL assembly doesn't handle #UD, thus making SEAMCALL when VMX is disabled would cause Oops. Unfortunately, there are legal cases that SEAMCALL can be made when VMX is disabled. For instance, VMX can be disabled due to emergency reboot while there are still TDX guests running. Extend the TDX_MODULE_CALL assembly to return an error code for #UD to handle this case gracefully, e.g., KVM can then quietly eat all SEAMCALL errors caused by emergency reboot. SEAMCALL instruction also causes #GP when TDX isn't enabled by the BIOS. Use _ASM_EXTABLE_FAULT() to catch both exceptions with the trap number recorded, and define two new error codes by XORing the trap number to the TDX_SW_ERROR. This opportunistically handles #GP too while using the same simple assembly code. A bonus is when kernel mistakenly calls SEAMCALL when CPU isn't in VMX operation, or when TDX isn't enabled by the BIOS, or when the BIOS is buggy, the kernel can get a nicer error code rather than a less understandable Oops. This is basically based on Peter's code. Suggested-by: Peter Zijlstra Signed-off-by: Kai Huang Signed-off-by: Dave Hansen Reviewed-by: Kirill A. Shutemov Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/all/de975832a367f476aab2d0eb0d9de66019a16b54.1692096753.git.kai.huang%40intel.com --- arch/x86/virt/vmx/tdx/tdxcall.S | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) (limited to 'arch/x86/virt') diff --git a/arch/x86/virt/vmx/tdx/tdxcall.S b/arch/x86/virt/vmx/tdx/tdxcall.S index 3f0b83a9977e..016a2a1ec1d6 100644 --- a/arch/x86/virt/vmx/tdx/tdxcall.S +++ b/arch/x86/virt/vmx/tdx/tdxcall.S @@ -1,6 +1,7 @@ /* SPDX-License-Identifier: GPL-2.0 */ #include #include +#include #include /* @@ -85,6 +86,7 @@ .endif /* \saved */ .if \host +.Lseamcall\@: seamcall /* * SEAMCALL instruction is essentially a VMExit from VMX root @@ -191,11 +193,28 @@ .if \host .Lseamcall_vmfailinvalid\@: mov $TDX_SEAMCALL_VMFAILINVALID, %rax + jmp .Lseamcall_fail\@ + +.Lseamcall_trap\@: + /* + * SEAMCALL caused #GP or #UD. By reaching here RAX contains + * the trap number. Convert the trap number to the TDX error + * code by setting TDX_SW_ERROR to the high 32-bits of RAX. + * + * Note cannot OR TDX_SW_ERROR directly to RAX as OR instruction + * only accepts 32-bit immediate at most. + */ + movq $TDX_SW_ERROR, %rdi + orq %rdi, %rax + +.Lseamcall_fail\@: .if \ret && \saved /* pop the unused structure pointer back to RSI */ popq %rsi .endif jmp .Lout\@ + + _ASM_EXTABLE_FAULT(.Lseamcall\@, .Lseamcall_trap\@) .endif /* \host */ .endm -- cgit v1.2.3-73-gaa49b