linux-kernel - [PATCHv2 28/29] x86/tdx: Warn about unexpected WBINVD

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Date:   Mon, 24 Jan 2022 18:02:14 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...el.com, luto@...nel.org, peterz@...radead.org
Cc:     sathyanarayanan.kuppuswamy@...ux.intel.com, aarcange@...hat.com,
        ak@...ux.intel.com, dan.j.williams@...el.com, david@...hat.com,
        hpa@...or.com, jgross@...e.com, jmattson@...gle.com,
        joro@...tes.org, jpoimboe@...hat.com, knsathya@...nel.org,
        pbonzini@...hat.com, sdeep@...are.com, seanjc@...gle.com,
        tony.luck@...el.com, vkuznets@...hat.com, wanpengli@...cent.com,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCHv2 28/29] x86/tdx: Warn about unexpected WBINVD

WBINVD causes #VE in TDX guests. There's no reliable way to emulate it.
The kernel can ask for VMM assistance, but VMM is untrusted and can ignore
the request.

Fortunately, there is no use case for WBINVD inside TDX guests.

Warn about any unexpected WBINVD.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 arch/x86/kernel/tdx.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
index 6048887ac846..22c785c2059c 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -530,6 +530,10 @@ static bool tdx_virt_exception_kernel(struct pt_regs *regs, struct ve_info *ve)
 	case EXIT_REASON_IO_INSTRUCTION:
 		ret = tdx_handle_io(regs, ve->exit_qual);
 		break;
+	case EXIT_REASON_WBINVD:
+		WARN_ONCE(1, "Unexpected WBINVD\n");
+		ret = true;
+		break;
 	default:
 		pr_warn("Unexpected #VE: %lld\n", ve->exit_reason);
 		break;
-- 
2.34.1