linux-kernel - [PATCH V4 3/4] x86/tdx: Emit warning if IRQs are enabled during HLT #VE handling

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250212000747.3403836-4-vannapurve@google.com>
Date: Wed, 12 Feb 2025 00:07:46 +0000
From: Vishal Annapurve <vannapurve@...gle.com>
To: x86@...nel.org, linux-kernel@...r.kernel.org
Cc: pbonzini@...hat.com, seanjc@...gle.com, erdemaktas@...gle.com, 
	ackerleytng@...gle.com, jxgao@...gle.com, sagis@...gle.com, oupton@...gle.com, 
	pgonda@...gle.com, kirill@...temov.name, dave.hansen@...ux.intel.com, 
	linux-coco@...ts.linux.dev, chao.p.peng@...ux.intel.com, 
	isaku.yamahata@...il.com, sathyanarayanan.kuppuswamy@...ux.intel.com, 
	Vishal Annapurve <vannapurve@...gle.com>, 
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH V4 3/4] x86/tdx: Emit warning if IRQs are enabled during HLT
 #VE handling

Direct HLT instruction execution causes #VEs for TDX VMs which is routed
to hypervisor via TDCALL. safe_halt() routines execute HLT in STI-shadow
so IRQs need to remain disabled until the TDCALL to ensure that pending
IRQs are correctly treated as wake events.

Emit warning and fail emulation if IRQs are enabled during HLT #VE handling
to avoid running into scenarios where IRQ wake events are lost resulting in
indefinite HLT execution times.

Reviewed-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Signed-off-by: Vishal Annapurve <vannapurve@...gle.com>
---
 arch/x86/coco/tdx/tdx.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index ee67c1870e70..54baf93d9218 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -393,6 +393,14 @@ static int handle_halt(struct ve_info *ve)
 {
 	const bool irq_disabled = irqs_disabled();
 
+	/*
+	 * HLT with IRQs enabled is unsafe, as an IRQ that is intended to be a
+	 * wake event may be consumed before requesting HLT emulation, leaving
+	 * the vCPU blocking indefinitely.
+	 */
+	if (WARN_ONCE(!irq_disabled, "HLT emulation with IRQs enabled"))
+		return -EIO;
+
 	if (__halt(irq_disabled))
 		return -EIO;
 
-- 
2.48.1.502.g6dc24dfdaf-goog