linux-kernel - Re: [RFC PATCH v7 01/37] KVM: lapic: Remove __apic_test_and_{set|clear}

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Message-ID: <20250623112612.GEaFk51EOLBBvZWWJm@fat_crate.local>
Date: Mon, 23 Jun 2025 13:26:12 +0200
From: Borislav Petkov <bp@...en8.de>
To: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
Cc: 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,
	kirill.shutemov@...ux.intel.com, huibo.wang@....com,
	naveen.rao@....com, francescolavra.fl@...il.com,
	tiala@...rosoft.com
Subject: Re: [RFC PATCH v7 01/37] KVM: lapic: Remove
 __apic_test_and_{set|clear}_vector()

On Tue, Jun 10, 2025 at 11:23:48PM +0530, Neeraj Upadhyay wrote:
> Remove __apic_test_and_set_vector() and __apic_test_and_clear_vector(),
> because the _only_ register that's safe to modify with a non-atomic
> operation is ISR, because KVM isn't running the vCPU, i.e. hardware can't
> service an IRQ or process an EOI for the relevant (virtual) APIC.
> 
> No functional change intended.
> 
> Suggested-by: Sean Christopherson <seanjc@...gle.com>
> [Neeraj: Add "inline" for apic_vector_to_isr()]
> Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
> ---
> Changes since v6:
> 
>  - New change.
> 
>  arch/x86/kvm/lapic.c | 19 +++++++------------
>  1 file changed, 7 insertions(+), 12 deletions(-)

FWIW: LGTM.

:-)

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette