This is a note to let you know that I've just added the patch titled
x86/tdx: Allow 32-bit emulation by default
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-tdx-allow-32-bit-emulation-by-default.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From fa2627da89fd3dd10338f8fd17040c8403bad2c2 Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Date: Mon, 4 Dec 2023 11:31:41 +0300
Subject: x86/tdx: Allow 32-bit emulation by default
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
[ upstream commit f4116bfc44621882556bbf70f5284fbf429a5cf6 ]
32-bit emulation was disabled on TDX to prevent a possible attack by
a VMM injecting an interrupt on vector 0x80.
Now that int80_emulation() has a check for external interrupts the
limitation can be lifted.
To distinguish software interrupts from external ones, int80_emulation()
checks the APIC ISR bit relevant to the 0x80 vector. For
software interrupts, this bit will be 0.
On TDX, the VAPIC state (including ISR) is protected and cannot be
manipulated by the VMM. The ISR bit is set by the microcode flow during
the handling of posted interrupts.
[ dhansen: more changelog tweaks ]
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v6.0+
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/coco/tdx/tdx.c | 9 ---------
1 file changed, 9 deletions(-)
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -821,14 +821,5 @@ void __init tdx_early_init(void)
*/
x86_cpuinit.parallel_bringup = false;
- /*
- * The VMM is capable of injecting interrupt 0x80 and triggering the
- * compatibility syscall path.
- *
- * By default, the 32-bit emulation is disabled in order to ensure
- * the safety of the VM.
- */
- ia32_disable();
-
pr_info("Guest detected\n");
}
Patches currently in stable-queue which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
queue-6.6/x86-entry-convert-int-0x80-emulation-to-idtentry.patch
queue-6.6/x86-coco-disable-32-bit-emulation-by-default-on-tdx-and-sev.patch
queue-6.6/x86-entry-do-not-allow-external-0x80-interrupts.patch
queue-6.6/x86-tdx-allow-32-bit-emulation-by-default.patch
