From: Thomas Gleixner <tglx@linutronix.de>
To: K Prateek Nayak <kprateek.nayak@amd.com>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
x86@kernel.org
Cc: Naveen rao <naveen.rao@amd.com>,
Sairaj Kodilkar <sarunkod@amd.com>,
"H. Peter Anvin" <hpa@zytor.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
"Xin Li (Intel)" <xin@zytor.com>,
Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Mario Limonciello <mario.limonciello@amd.com>,
"Gautham R. Shenoy" <gautham.shenoy@amd.com>,
Babu Moger <babu.moger@amd.com>,
Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
K Prateek Nayak <kprateek.nayak@amd.com>
Subject: Re: [PATCH v3 4/4] x86/cpu/topology: Check for X86_FEATURE_XTOPOLOGY instead of passing has_topoext
Date: Sun, 24 Aug 2025 16:55:24 +0200 [thread overview]
Message-ID: <87jz2s3h2b.ffs@tglx> (raw)
In-Reply-To: <87ms7o3kn6.ffs@tglx>
On Sun, Aug 24 2025 at 15:38, Thomas Gleixner wrote:
>> - if (!has_topoext) {
>> + if (!cpu_feature_enabled(X86_FEATURE_XTOPOLOGY)) {
>> /*
>> * Prefer initial_apicid parsed from XTOPOLOGY leaf
>> * 0x8000026 or 0xb if available. Otherwise prefer the
>
> That's patently wrong.
>
> The leaves might be "available", but are not guaranteed to be valid. So
> FEATURE_XTOPOLOGY gives you the wrong answer.
>
> The has_topoext logic is there for a reason.
Hrm. I have to correct myself. It's set by the 0xb... parsing when that
finds a valid leaf. My memory tricked me on that.
So yes, it can be used for that, but that's a cleanup. The simple fix
should be applied first as that's trivial to backport.
next prev parent reply other threads:[~2025-08-24 14:55 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-18 6:04 [PATCH v3 0/4] x86/cpu/topology: Work around the nuances of virtualization on AMD/Hygon K Prateek Nayak
2025-08-18 6:04 ` [PATCH v3 1/4] x86/msr-index: Define AMD64_CPUID_FN_EXT MSR K Prateek Nayak
2025-08-18 6:04 ` [PATCH v3 2/4] x86/cpu/topology: Use initial APICID from XTOPOEXT on AMD/HYGON K Prateek Nayak
2025-08-18 6:04 ` [PATCH v3 3/4] x86/cpu/topology: Always try cpu_parse_topology_ext() on AMD/Hygon K Prateek Nayak
2025-08-18 6:04 ` [PATCH v3 4/4] x86/cpu/topology: Check for X86_FEATURE_XTOPOLOGY instead of passing has_topoext K Prateek Nayak
2025-08-24 13:38 ` Thomas Gleixner
2025-08-24 14:55 ` Thomas Gleixner [this message]
2025-08-25 4:05 ` K Prateek Nayak
2025-08-19 11:34 ` [PATCH v3 0/4] x86/cpu/topology: Work around the nuances of virtualization on AMD/Hygon Borislav Petkov
2025-08-19 14:28 ` K Prateek Nayak
2025-08-19 21:24 ` Borislav Petkov
2025-08-20 8:11 ` Naveen N Rao
2025-08-20 8:59 ` Borislav Petkov
2025-08-20 9:12 ` K Prateek Nayak
2025-08-20 9:28 ` Borislav Petkov
2025-08-20 9:59 ` Gautham R. Shenoy
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