linux-kernel - RE: [RFC PATCH 5/6] x86/Hyper-V: Not use auto-eoi when Secure AVIC is available

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Message-ID:
 <SN6PR02MB41578854FF8D79504DB847A0D491A@SN6PR02MB4157.namprd02.prod.outlook.com>
Date: Wed, 14 May 2025 16:54:49 +0000
From: Michael Kelley <mhklinux@...look.com>
To: Tianyu Lan <ltykernel@...il.com>, "kys@...rosoft.com" <kys@...rosoft.com>,
	"haiyangz@...rosoft.com" <haiyangz@...rosoft.com>, "wei.liu@...nel.org"
	<wei.liu@...nel.org>, "decui@...rosoft.com" <decui@...rosoft.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>, "mingo@...hat.com"
	<mingo@...hat.com>, "bp@...en8.de" <bp@...en8.de>,
	"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>, "x86@...nel.org"
	<x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>, "Neeraj.Upadhyay@....com"
	<Neeraj.Upadhyay@....com>, "yuehaibing@...wei.com" <yuehaibing@...wei.com>,
	"kvijayab@....com" <kvijayab@....com>, "jacob.jun.pan@...ux.intel.com"
	<jacob.jun.pan@...ux.intel.com>, "jpoimboe@...nel.org" <jpoimboe@...nel.org>,
	"tiala@...rosoft.com" <tiala@...rosoft.com>
CC: "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [RFC PATCH 5/6] x86/Hyper-V: Not use auto-eoi when Secure AVIC is
 available

From: Tianyu Lan <ltykernel@...il.com> Sent: Tuesday, May 6, 2025 6:07 AM
> 

For the patch Subject, use:

x86/hyperv: Don't use auto-EOI when Secure AVIC is available

> Hyper-V doesn't support auto-eoi with Secure AVIC.
> So Enable HV_DEPRECATING_AEOI_RECOMMENDED flag

s/Enable/enable/
> to force to write eoi register after handling interrupt.

"to force writing the EOI register after handling an interrupt."

> 
> Signed-off-by: Tianyu Lan <tiala@...rosoft.com>
> ---
>  arch/x86/kernel/cpu/mshyperv.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index 3e2533954675..fbe45b5e9790 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -463,6 +463,9 @@ static void __init ms_hyperv_init_platform(void)
> 
>  	hv_identify_partition_type();
> 
> +	if (cc_platform_has(CC_ATTR_SNP_SECURE_AVIC))
> +		ms_hyperv.hints |= HV_DEPRECATING_AEOI_RECOMMENDED;
> +

Shouldn't Hyper-V already be setting this flag if it is offering Secure AVIC
to guests? I guess it doesn't hurt to do this in the Linux code, but it seems
like it should be Hyper-V's responsibility.

Michael

>  	if (ms_hyperv.hints & HV_X64_HYPERV_NESTED) {
>  		hv_nested = true;
>  		pr_info("Hyper-V: running on a nested hypervisor\n");
> --
> 2.25.1
>