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Subject: Re: [RFC v2-fix-v2 2/2] x86/tdx: Handle in-kernel MMIO
To:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@intel.com>,
        Tony Luck <tony.luck@intel.com>
Cc:     Kirill Shutemov <kirill.shutemov@linux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@kernel.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Raj Ashok <ashok.raj@intel.com>,
        Sean Christopherson <seanjc@google.com>,
        linux-kernel@vger.kernel.org
References: <3e9a26c3-8eee-88f5-f8e2-8a2dd2c028ea@intel.com>
 <20210602194220.2227863-1-sathyanarayanan.kuppuswamy@linux.intel.com>
 <20210602194220.2227863-3-sathyanarayanan.kuppuswamy@linux.intel.com>
From:   Andi Kleen <ak@linux.intel.com>
Message-ID: <aac39d2e-c812-71c0-c769-e505ff6c5b40@linux.intel.com>
Date:   Wed, 2 Jun 2021 14:01:26 -0700
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User-space
> access triggers SIGBUS.

Actually it looks like it's implemented below now, so that sentence 
could be dropped.


> +
> +	if (user_mode(regs)) {
> +		ret = insn_fetch_from_user(regs, buffer);
> +		if (!ret)
> +			return -EFAULT;
> +		if (!insn_decode_from_regs(&insn, regs, buffer, ret))
> +			return -EFAULT;
> +	} else {
> +		ret = copy_from_kernel_nofault(buffer, (void *)regs->ip,
> +					       MAX_INSN_SIZE);
> +		if (ret)
> +			return -EFAULT;
> +		insn_init(&insn, buffer, MAX_INSN_SIZE, 1);
> +		insn_get_length(&insn);
> +	}
> +