From: Thomas Gleixner <tglx@linutronix.de>
To: Sean Christopherson <seanjc@google.com>
Cc: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>,
linux-kernel@vger.kernel.org, bp@alien8.de, mingo@redhat.com,
dave.hansen@linux.intel.com, Thomas.Lendacky@amd.com,
nikunj@amd.com, Santosh.Shukla@amd.com, Vasant.Hegde@amd.com,
Suravee.Suthikulpanit@amd.com, David.Kaplan@amd.com,
x86@kernel.org, hpa@zytor.com, peterz@infradead.org,
pbonzini@redhat.com, kvm@vger.kernel.org,
kirill.shutemov@linux.intel.com, huibo.wang@amd.com,
naveen.rao@amd.com
Subject: Re: [RFC v2 13/17] x86/apic: Handle EOI writes for SAVIC guests
Date: Thu, 27 Mar 2025 11:48:43 +0100 [thread overview]
Message-ID: <87y0wqycj8.ffs@tglx> (raw)
In-Reply-To: <Z92dqEhfj1GG6Fxb@google.com>
On Fri, Mar 21 2025 at 10:11, Sean Christopherson wrote:
> On Fri, Mar 21, 2025, Thomas Gleixner wrote:
>>
>> Congrats. You managed to re-implement find_last_bit() in the most
>> incomprehesible way.
>
> Heh, having burned myself quite badly by trying to use find_last_bit() to get
> pending/in-service IRQs in KVM code...
>
> Using find_last_bit() doesn't work because the ISR chunks aren't contiguous,
> they're 4-byte registers at 16-byte strides.
Which is obvious to solve with trivial integer math:
bit = vector + 32 * (vector / 32);
ergo
vector = bit - 16 * (bit / 32);
No?
> That said, copy+pasting the aforementioned KVM code is absurd. Please extract
> KVM's find_highest_vector() to common code.
No. Reimplement this with find_last_bit() and the trivial adjustment
above and remove find_highest_vector() as there is no point to
proliferate a bad reimplementation of find_last_bit().
Thanks,
tglx
next prev parent reply other threads:[~2025-03-27 10:48 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-26 9:05 [RFC v2 00/17] AMD: Add Secure AVIC Guest Support Neeraj Upadhyay
2025-02-26 9:05 ` [RFC v2 01/17] x86/apic: Add new driver for Secure AVIC Neeraj Upadhyay
2025-03-20 15:51 ` Borislav Petkov
2025-03-21 3:44 ` Neeraj Upadhyay
2025-03-21 13:55 ` Borislav Petkov
2025-03-21 16:09 ` Neeraj Upadhyay
2025-03-21 17:11 ` Borislav Petkov
2025-04-01 5:12 ` Neeraj Upadhyay
2025-04-02 9:47 ` Borislav Petkov
2025-04-02 10:34 ` Neeraj Upadhyay
2025-04-07 13:17 ` Borislav Petkov
2025-04-07 16:17 ` Neeraj Upadhyay
2025-03-21 12:44 ` Thomas Gleixner
2025-03-21 13:52 ` Borislav Petkov
2025-03-21 12:53 ` Thomas Gleixner
2025-03-21 13:25 ` Neeraj Upadhyay
2025-02-26 9:05 ` [RFC v2 02/17] x86/apic: Initialize Secure AVIC APIC backing page Neeraj Upadhyay
2025-03-21 13:08 ` Thomas Gleixner
2025-03-21 13:49 ` Neeraj Upadhyay
2025-03-21 16:32 ` Francesco Lavra
2025-03-21 17:00 ` Neeraj Upadhyay
2025-02-26 9:05 ` [RFC v2 03/17] x86/apic: Populate .read()/.write() callbacks of Secure AVIC driver Neeraj Upadhyay
2025-03-21 13:38 ` Thomas Gleixner
2025-03-21 14:00 ` Neeraj Upadhyay
2025-02-26 9:05 ` [RFC v2 04/17] x86/apic: Initialize APIC ID for Secure AVIC Neeraj Upadhyay
2025-03-21 13:52 ` Thomas Gleixner
2025-03-21 15:11 ` Neeraj Upadhyay
2025-02-26 9:05 ` [RFC v2 05/17] x86/apic: Add update_vector callback " Neeraj Upadhyay
2025-03-21 14:27 ` Thomas Gleixner
2025-03-21 15:35 ` Neeraj Upadhyay
2025-03-25 12:10 ` Neeraj Upadhyay
2025-03-27 10:27 ` Thomas Gleixner
2025-03-27 11:17 ` Neeraj Upadhyay
2025-03-27 12:18 ` Thomas Gleixner
2025-03-27 12:30 ` Neeraj Upadhyay
2025-02-26 9:05 ` [RFC v2 06/17] x86/apic: Add support to send IPI " Neeraj Upadhyay
2025-03-21 15:06 ` Thomas Gleixner
2025-04-01 10:25 ` Neeraj Upadhyay
2025-02-26 9:05 ` [RFC v2 07/17] x86/apic: Support LAPIC timer " Neeraj Upadhyay
2025-02-26 9:05 ` [RFC v2 08/17] x86/sev: Initialize VGIF for secondary VCPUs " Neeraj Upadhyay
2025-02-26 9:05 ` [RFC v2 09/17] x86/apic: Add support to send NMI IPI " Neeraj Upadhyay
2025-02-26 9:05 ` [RFC v2 10/17] x86/apic: Allow NMI to be injected from hypervisor " Neeraj Upadhyay
2025-02-26 9:05 ` [RFC v2 11/17] x86/sev: Enable NMI support " Neeraj Upadhyay
2025-02-26 9:05 ` [RFC v2 12/17] x86/apic: Read and write LVT* APIC registers from HV for SAVIC guests Neeraj Upadhyay
2025-02-26 9:05 ` [RFC v2 13/17] x86/apic: Handle EOI writes " Neeraj Upadhyay
2025-03-21 15:41 ` Thomas Gleixner
2025-03-21 17:11 ` Sean Christopherson
2025-03-27 10:48 ` Thomas Gleixner [this message]
2025-03-27 12:20 ` Thomas Gleixner
2025-03-27 14:19 ` Sean Christopherson
2025-03-27 16:54 ` Thomas Gleixner
2025-02-26 9:05 ` [RFC v2 14/17] x86/apic: Add kexec support for Secure AVIC Neeraj Upadhyay
2025-03-21 15:48 ` Thomas Gleixner
2025-04-01 10:35 ` Neeraj Upadhyay
2025-04-01 18:31 ` Thomas Gleixner
2025-04-02 2:40 ` Neeraj Upadhyay
2025-02-26 9:05 ` [RFC v2 15/17] x86/apic: Enable Secure AVIC in Control MSR Neeraj Upadhyay
2025-02-26 9:05 ` [RFC v2 16/17] x86/sev: Prevent SECURE_AVIC_CONTROL MSR interception for Secure AVIC guests Neeraj Upadhyay
2025-02-26 9:05 ` [RFC v2 17/17] x86/sev: Indicate SEV-SNP guest supports Secure AVIC Neeraj Upadhyay
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