From: "H. Peter Anvin" <hpa@zytor.com>
To: Dave Hansen <dave.hansen@intel.com>,
"Xin Li (Intel)" <xin@zytor.com>,
linux-kernel@vger.kernel.org
Cc: luto@kernel.org, tglx@linutronix.de, mingo@redhat.com,
bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org,
jmill@asu.edu, peterz@infradead.org, andrew.cooper3@citrix.com,
stable@vger.kernel.org
Subject: Re: [PATCH v3 1/1] x86/fred: Remove ENDBR64 from FRED entry points
Date: Wed, 13 Aug 2025 14:57:55 -0700 [thread overview]
Message-ID: <d0cac7d8-3036-4241-b11c-f005224daefd@zytor.com> (raw)
In-Reply-To: <e5a7d108-f900-4a63-8116-c9eb54171976@intel.com>
On 2025-08-13 14:07, Dave Hansen wrote:
> On 7/15/25 23:33, Xin Li (Intel) wrote:
>> The FRED specification has been changed in v9.0 to state that there
>> is no need for FRED event handlers to begin with ENDBR64, because
>> in the presence of supervisor indirect branch tracking, FRED event
>> delivery does not enter the WAIT_FOR_ENDBRANCH state.
>>
>> As a result, remove ENDBR64 from FRED entry points.
>
> So, the spec is being updated or has been updated to reflect the new
> architecture, right?
>
> Remind me, are there no FRED systems out in the wild today, so we don't
> have to worry about breaking anything?
Correct. The FRED v9 spec contains this change.
All production hardware and late pre-production hardware will have this.
-hpa
prev parent reply other threads:[~2025-08-13 21:59 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-16 6:33 Xin Li (Intel)
2025-08-11 22:48 ` Xin Li
2025-08-13 21:07 ` Dave Hansen
2025-08-13 21:57 ` H. Peter Anvin [this message]
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