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Date:   Tue, 28 Nov 2023 12:06:41 +0100
From:   Roger Pau =?utf-8?B?TW9ubsOp?= <roger.pau@citrix.com>
To:     Juergen Gross <jgross@suse.com>
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>, xen-devel@lists.xenproject.org
Subject: Re: [PATCH] x86/xen: fix percpu vcpu_info allocation
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References: <20231124074852.25161-1-jgross@suse.com>
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On Fri, Nov 24, 2023 at 08:48:52AM +0100, Juergen Gross wrote:
> Today the percpu struct vcpu_info is allocated via DEFINE_PER_CPU(),
> meaning that it could cross a page boundary. In this case registering
> it with the hypervisor will fail, resulting in a panic().
> 
> This can easily be fixed by using DEFINE_PER_CPU_ALIGNED() instead,
> as struct vcpu_info is guaranteed to have a size of 64 bytes, matching
> the cache line size of x86 64-bit processors (Xen doesn't support
> 32-bit processors).
> 
> Fixes: 5ead97c84fa7 ("xen: Core Xen implementation")
> Signed-off-by: Juergen Gross <jgross@suse.com>

FWIW, on FreeBSD we also switched to the same approach quite
recently:

https://cgit.freebsd.org/src/commit/sys/xen/xen_common.c?id=20fc5bf7df1db698f2651eaa04a3bc71290e1636

Should have checked the Linux side, sorry.

Roger.