linux-kernel - RE: [PATCH V2 1/3] x86/Hyper-V: Set x2apic destination mode to physical when x2apic is available

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Date:   Sun, 3 Feb 2019 21:26:11 +0000
From:   Michael Kelley <mikelley@...rosoft.com>
To:     "lantianyu1986@...il.com" <lantianyu1986@...il.com>
CC:     Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "sashal@...nel.org" <sashal@...nel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>, "hpa@...or.com" <hpa@...or.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "joro@...tes.org" <joro@...tes.org>,
        "mchehab+samsung@...nel.org" <mchehab+samsung@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "nicolas.ferre@...rochip.com" <nicolas.ferre@...rochip.com>,
        "arnd@...db.de" <arnd@...db.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        vkuznets <vkuznets@...hat.com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "dan.carpenter@...cle.com" <dan.carpenter@...cle.com>
Subject: RE: [PATCH V2 1/3] x86/Hyper-V: Set x2apic destination mode to
 physical when x2apic is available

From: lantianyu1986@...il.com <lantianyu1986@...il.com>  Sent: Saturday, February 2, 2019 5:15 AM
> 
> Hyper-V doesn't provide irq remapping for IO-APIC. To enable x2apic,
> set x2apic destination mode to physcial mode when x2apic is available
> and Hyper-V IOMMU driver makes sure cpus assigned with IO-APIC irqs have
> 8-bit APIC id.
> 
> Signed-off-by: Lan Tianyu <Tianyu.Lan@...rosoft.com>
> ---
> Change since v1:
>        - Remove redundant extern for x2apic_phys
> ---
>  arch/x86/kernel/cpu/mshyperv.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index e81a2db..4bd6d90 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -328,6 +328,16 @@ static void __init ms_hyperv_init_platform(void)
>  # ifdef CONFIG_SMP
>  	smp_ops.smp_prepare_boot_cpu = hv_smp_prepare_boot_cpu;
>  # endif
> +
> +/*
> + * Hyper-V doesn't provide irq remapping for IO-APIC. To enable x2apic,
> + * set x2apic destination mode to physcial mode when x2apic is available
> + * and Hyper-V IOMMU driver makes sure cpus assigned with IO-APIC irqs
> + * have 8-bit APIC id.
> + */

Per comment from Dan Carpenter on v1 of this patch, the above comment
block should be indented one tab to line up with the "if" statement below.

Michael

> +	if (IS_ENABLED(CONFIG_HYPERV_IOMMU) && x2apic_supported())
> +		x2apic_phys = 1;
> +
>  #endif
>  }
> 
> --
> 2.7.4