linux-kernel - Re: [RFC 02/14] x86/apic: Initialize Secure AVIC APIC backing page

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Message-ID: <20241023163029.GEZxkkpdfkxdHWTHAW@fat_crate.local>
Date: Wed, 23 Oct 2024 18:30:29 +0200
From: Borislav Petkov <bp@...en8.de>
To: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
Cc: Dave Hansen <dave.hansen@...el.com>, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, mingo@...hat.com, dave.hansen@...ux.intel.com,
	Thomas.Lendacky@....com, nikunj@....com, Santosh.Shukla@....com,
	Vasant.Hegde@....com, Suravee.Suthikulpanit@....com,
	David.Kaplan@....com, x86@...nel.org, hpa@...or.com,
	peterz@...radead.org, seanjc@...gle.com, pbonzini@...hat.com,
	kvm@...r.kernel.org
Subject: Re: [RFC 02/14] x86/apic: Initialize Secure AVIC APIC backing page

On Wed, Oct 09, 2024 at 11:22:58PM +0530, Neeraj Upadhyay wrote:
> I will start with 4K. For later, I will get the performance numbers to propose
> a change in allocation scheme  - for ex, allocating a bigger contiguous
> batch from the total allocation required for backing pages (num_possible_cpus() * 4K)
> without doing 2M reservation.

Why does performance matter here if you're going to allocate simply a 4K page
per vCPU and set them all up in the APIC setup path? And then you can do the
page conversion to guest-owned as part of the guest vCPU init path?

-- 
Regards/Gruss,
    Boris.

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