linux-kernel - RE: [EXTERNAL] Re: [PATCH hyperv-next] x86/hyperv: Fix APIC ID and VP ID confusion in hv_snp_boot

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Message-ID:
 <KUZP153MB1444118E6199CBED8C78E6D4BE842@KUZP153MB1444.APCP153.PROD.OUTLOOK.COM>
Date: Fri, 25 Apr 2025 09:14:06 +0000
From: Saurabh Singh Sengar <ssengar@...rosoft.com>
To: Wei Liu <wei.liu@...nel.org>, Roman Kisel <romank@...ux.microsoft.com>
CC: "bp@...en8.de" <bp@...en8.de>, "dave.hansen@...ux.intel.com"
	<dave.hansen@...ux.intel.com>, Dexuan Cui <decui@...rosoft.com>, Haiyang
 Zhang <haiyangz@...rosoft.com>, "hpa@...or.com" <hpa@...or.com>, KY
 Srinivasan <kys@...rosoft.com>, "mikelley@...rosoft.com"
	<mikelley@...rosoft.com>, "mingo@...hat.com" <mingo@...hat.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>, Tianyu Lan
	<Tianyu.Lan@...rosoft.com>, "linux-hyperv@...r.kernel.org"
	<linux-hyperv@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "x86@...nel.org" <x86@...nel.org>, Allen Pais
	<apais@...rosoft.com>, Ben Hillis <Ben.Hillis@...rosoft.com>, Brian Perkins
	<Brian.Perkins@...rosoft.com>, Sunil Muthuswamy <sunilmut@...rosoft.com>
Subject: RE: [EXTERNAL] Re: [PATCH hyperv-next] x86/hyperv: Fix APIC ID and VP
 ID confusion in hv_snp_boot_ap()

> 
> On Thu, Apr 24, 2025 at 02:57:46PM -0700, Roman Kisel wrote:
> > To start an application processor in SNP-isolated guest, a hypercall
> > is used that takes a virtual processor index. The hv_snp_boot_ap()
> > function uses that START_VP hypercall but passes as VP ID to it what
> > it receives as a wakeup_secondary_cpu_64 callback: the APIC ID.
> >
> > As those two aren't generally interchangeable, that may lead to hung
> > APs if VP IDs and APIC IDs don't match, e.g. APIC IDs might be sparse
> > whereas VP IDs never are.
> >
> > Update the parameter names to avoid confusion as to what the parameter
> > is. Use the APIC ID to VP ID conversion to provide correct input to
> > the hypercall.
> >
> > Cc: stable@...r.kernel.org
> > Fixes: 44676bb9d566 ("x86/hyperv: Add smp support for SEV-SNP guest")
> > Signed-off-by: Roman Kisel <romank@...ux.microsoft.com>
> 
> Applied to hyperv-fixes.

This patch will break the builds.

Roman,
Have you tested this patch on the latest linux-next ?

Regards,
Saurabh