From: "H. Peter Anvin" <hpa@zytor.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>,
"Lai, Yi" <yi1.lai@linux.intel.com>, Xin Li <xin@zytor.com>
Cc: Dave Hansen <dave.hansen@intel.com>,
yi1.lai@intel.com, bp@alien8.de, dave.hansen@linux.intel.com,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
luto@kernel.org, mingo@redhat.com, shuah@kernel.org,
tglx@kernel.org, x86@kernel.org
Subject: Re: [PATCH] selftests/x86: Fix sysret_rip assertion failure on FRED systems
Date: Mon, 23 Mar 2026 13:27:40 -0700 [thread overview]
Message-ID: <0200a8d8-6871-4ff2-8c6a-968c2cb39a4f@zytor.com> (raw)
In-Reply-To: <c2979413-62f4-4a35-ad64-be2b8f55ea04@citrix.com>
On 2026-03-23 12:17, Andrew Cooper wrote:
>
> This doesn't really test whether FRED is active. It tests whether the
> OS is not providing strict backwards compatibility, and I think will
> malfunction when there's a hypervisor above Linux providing strict
> backwards compatibility.
>
But that applies equally to IRET, no? If the hypervisor clobbers the segment
selector like IRET would in the interest of compatibility then you have the
same issue.
If the guest is running a FRED kernel and the hypervisor goes in and mucks
with the state after ERETU behind the kernel's back I think you have a much,
much bigger problem.
-hpa
next prev parent reply other threads:[~2026-03-23 20:44 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-20 6:33 Yi Lai
2026-03-20 14:31 ` Dave Hansen
2026-03-20 15:47 ` Andrew Cooper
2026-03-20 15:50 ` Dave Hansen
2026-03-22 6:13 ` Xin Li
2026-03-23 6:06 ` Lai, Yi
2026-03-23 16:19 ` Xin Li
2026-03-23 19:11 ` H. Peter Anvin
2026-03-23 19:17 ` Andrew Cooper
2026-03-23 20:27 ` H. Peter Anvin [this message]
2026-03-24 14:08 ` Andrew Cooper
2026-03-24 14:33 ` H. Peter Anvin
2026-03-24 14:46 ` Andrew Cooper
2026-03-24 15:16 ` H. Peter Anvin
2026-03-22 20:08 ` H. Peter Anvin
2026-03-23 5:55 ` Lai, Yi
2026-03-23 16:39 ` Andrew Cooper
2026-03-24 1:28 ` Lai, Yi
2026-03-24 11:08 ` David Laight
2026-03-24 14:31 ` H. Peter Anvin
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