From: "H. Peter Anvin" <hpa@zytor.com>
To: "Luck, Tony" <tony.luck@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"x86@kernel.org" <x86@kernel.org>,
Josh Poimboeuf <jpoimboe@kernel.org>,
"Lutomirski, Andy" <luto@kernel.org>,
Jonathan Corbet <corbet@lwn.net>, "Christopherson,,
Sean" <seanjc@google.com>, Paolo Bonzini <pbonzini@redhat.com>,
"ak@linux.intel.com" <ak@linux.intel.com>,
"tim.c.chen@linux.intel.com" <tim.c.chen@linux.intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
Alyssa Milburn <alyssa.milburn@linux.intel.com>,
Daniel Sneddon <daniel.sneddon@linux.intel.com>,
"antonio.gomez.iglesias@linux.intel.com"
<antonio.gomez.iglesias@linux.intel.com>,
"Milburn, Alyssa" <alyssa.milburn@intel.com>
Subject: RE: [PATCH v2 1/6] x86/bugs: Add asm helpers for executing VERW
Date: Tue, 24 Oct 2023 12:14:25 -0700 [thread overview]
Message-ID: <5B8EB5F2-16A7-47BC-97FE-262ED0169DE3@zytor.com> (raw)
In-Reply-To: <SJ1PR11MB6083E3E2D35B30F4E40E8FE7FCDFA@SJ1PR11MB6083.namprd11.prod.outlook.com>
On October 24, 2023 11:49:07 AM PDT, "Luck, Tony" <tony.luck@intel.com> wrote:
>> the only overhead to modules other than load time (including the runtime linking) is that modules can't realistically be mapped using large page entries.
>
>If there were some significant win for using large pages, couldn't the
>kernel pre-allocate some 2MB pages in the [-2GiB,0) range? Boot parameter
>for how many (perhaps two for separate code/data pages). First few loaded
>modules get to use that space until it is all gone.
>
>It would all be quite messy if those modules were later unloaded/reloaded
>... so there would have to be some compelling benchmarks to justify
>the complexity.
>
>That's probably why Peter said "can't realistically".
>
>-Tony
>
Sure it could, but it would mean the kernel is sitting on an average of 6 MB of unusable memory. It would also mean that unloaded modules would create holes in that memory which would have to be managed.
next prev parent reply other threads:[~2023-10-24 19:15 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-24 8:08 [PATCH v2 0/6] Delay VERW Pawan Gupta
2023-10-24 8:08 ` [PATCH v2 1/6] x86/bugs: Add asm helpers for executing VERW Pawan Gupta
2023-10-24 10:36 ` Peter Zijlstra
2023-10-24 16:35 ` Pawan Gupta
2023-10-24 16:36 ` Peter Zijlstra
2023-10-24 16:45 ` Pawan Gupta
2023-10-24 17:02 ` Peter Zijlstra
2023-10-24 17:30 ` Pawan Gupta
2023-10-24 18:27 ` H. Peter Anvin
2023-10-24 18:49 ` Luck, Tony
2023-10-24 19:14 ` H. Peter Anvin [this message]
2023-10-24 19:40 ` Luck, Tony
2023-10-24 20:30 ` H. Peter Anvin
2023-10-24 22:30 ` Peter Zijlstra
2023-10-24 22:28 ` Peter Zijlstra
2023-10-25 4:00 ` Pawan Gupta
2023-10-25 6:56 ` Peter Zijlstra
2023-10-25 15:06 ` Pawan Gupta
2023-10-25 6:58 ` Peter Zijlstra
2023-10-25 15:10 ` Pawan Gupta
2023-10-24 8:08 ` [PATCH v2 2/6] x86/entry_64: Add VERW just before userspace transition Pawan Gupta
2023-10-24 8:08 ` [PATCH v2 3/6] x86/entry_32: " Pawan Gupta
2023-10-24 8:08 ` [PATCH v2 4/6] x86/bugs: Use ALTERNATIVE() instead of mds_user_clear static key Pawan Gupta
2023-10-25 22:08 ` kernel test robot
2023-10-24 8:08 ` [PATCH v2 5/6] KVM: VMX: Use BT+JNC, i.e. EFLAGS.CF to select VMRESUME vs. VMLAUNCH Pawan Gupta
2023-10-25 8:15 ` Nikolay Borisov
2023-10-24 8:08 ` [PATCH v2 6/6] KVM: VMX: Move VERW closer to VMentry for MDS mitigation Pawan Gupta
2023-10-25 7:47 ` Chao Gao
2023-10-25 15:15 ` Pawan Gupta
2023-10-24 12:26 ` [PATCH v2 0/6] Delay VERW Matthew Wilcox
2023-10-24 17:01 ` Pawan Gupta
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