linux-kernel - Re: [PATCH 11/22] KVM: x86: hyper-v: replace bitmap

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Message-ID: <Yop1R+Z7OtIcfrvA@yury-laptop>
Date:   Sun, 22 May 2022 10:39:19 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        David Laight <David.Laight@...lab.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Joe Perches <joe@...ches.com>,
        Julia Lawall <Julia.Lawall@...ia.fr>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        Nicholas Piggin <npiggin@...il.com>,
        Nicolas Palix <nicolas.palix@...g.fr>,
        Peter Zijlstra <peterz@...radead.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Matti Vaittinen <Matti.Vaittinen@...rohmeurope.com>,
        linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H . Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>, kvm@...r.kernel.org,
        x86@...nel.org
Subject: Re: [PATCH 11/22] KVM: x86: hyper-v: replace bitmap_weight() with
 hweight64()

On Sun, May 22, 2022 at 07:53:57AM -0700, Guenter Roeck wrote:
> On Tue, May 10, 2022 at 08:47:39AM -0700, Yury Norov wrote:
> > kvm_hv_flush_tlb() applies bitmap API to a u64 variable valid_bank_mask.
> > Since valid_bank_mask has a fixed size, we can use hweight64() and avoid
> > excessive bloating.
> 
> In kvm_hv_send_ipi(), valid_bank_mask is unsigned long, not u64.
> 
> This results in:
> 
> arch/x86/kvm/hyperv.c: In function 'kvm_hv_send_ipi':
> include/asm-generic/bitops/const_hweight.h:21:76: error: right shift count >= width of type
> 
> on all 32-bit builds.
> 
> Guenter

Hi Guenter,

The fix is in Paolo's tree:
https://lore.kernel.org/lkml/20220519171504.1238724-1-yury.norov@gmail.com/T/

Thanks,
Yury