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From:   Thomas Gleixner <tglx@linutronix.de>
To:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        mingo@redhat.com, bp@alien8.de, dave.hansen@intel.com,
        luto@kernel.org, peterz@infradead.org
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        hpa@zytor.com, jgross@suse.com, jmattson@google.com,
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        tony.luck@intel.com, vkuznets@redhat.com, wanpengli@tencent.com,
        x86@kernel.org, linux-kernel@vger.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCHv2 11/29] x86/boot: Allow to hook up alternative port I/O
 helpers
In-Reply-To: <20220124150215.36893-12-kirill.shutemov@linux.intel.com>
References: <20220124150215.36893-1-kirill.shutemov@linux.intel.com>
 <20220124150215.36893-12-kirill.shutemov@linux.intel.com>
Date:   Tue, 01 Feb 2022 23:39:09 +0100
Message-ID: <87k0eexlde.ffs@tglx>
MIME-Version: 1.0
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Precedence: bulk

On Mon, Jan 24 2022 at 18:01, Kirill A. Shutemov wrote:

> Port I/O instructions trigger #VE in the TDX environment. In response to
> the exception, kernel emulates these instructions using hypercalls.
>
> But during early boot, on the decompression stage, it is cumbersome to
> deal with #VE. It is cleaner to go to hypercalls directly, bypassing #VE
> handling.
>
> Add a way to hook up alternative port I/O helpers in the boot stub.
> All port I/O operations are routed via 'pio_ops'. By default 'pio_ops'
> initialized with native port I/O implementations.
>
> This is a preparation patch. The next patch will override 'pio_ops' if
> the kernel booted in the TDX environment.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

Aside of Borislav's comments:

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>