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Message-ID: <f7f82377-6127-79e3-07d8-def490c4e35c@intel.com>
Date:   Tue, 6 Jun 2023 11:14:29 -0700
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Subject: Re: [PATCHv3 2/3] x86/tdx: Fix race between set_memory_encrypted()
 and load_unaligned_zeropad()
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To:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        tglx@linutronix.de, mingo@redhat.com, bp@alien8.de
Cc:     decui@microsoft.com, rick.p.edgecombe@intel.com,
        sathyanarayanan.kuppuswamy@linux.intel.com, seanjc@google.com,
        thomas.lendacky@amd.com, x86@kernel.org,
        linux-kernel@vger.kernel.org
References: <20230606095622.1939-1-kirill.shutemov@linux.intel.com>
 <20230606095622.1939-3-kirill.shutemov@linux.intel.com>
From:   Dave Hansen <dave.hansen@intel.com>
In-Reply-To: <20230606095622.1939-3-kirill.shutemov@linux.intel.com>
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On 6/6/23 02:56, Kirill A. Shutemov wrote:
> load_unaligned_zeropad() can touch memory that is not owned by the
> caller, but just happened to next after the owned memory.
> This load_unaligned_zeropad() behaviour makes it important when kernel
> asks VMM to convert a GPA from shared to private or back. Kernel must
> never have a page mapped into direct mapping (and aliases) as private
> when the GPA is already converted to shared or when GPA is not yet
> converted to private.
> 
> load_unaligned_zeropad() can touch memory that is not owned by the
> caller, but just happens to be next after the owned memory. This
> load_unaligned_zeropad() behavior makes it important when the kernel
> asks VMM to convert a GPA from shared to private or back. The kernel
> must never have a page mapped into direct mapping (and aliases) as
> private when the GPA is already converted to shared or when the GPA is
> not yet converted to private.

Heh, that must be really important info to have it in the changelog twice!

I'll fix it up when I apply it.