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Date:   Tue, 23 May 2023 15:43:15 -0700
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Subject: Re: [PATCH v6 2/6] x86/tdx: Support vmalloc() for
 tdx_enc_status_changed()
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To:     kirill.shutemov@linux.intel.com
Cc:     Dexuan Cui <decui@microsoft.com>, ak@linux.intel.com,
        arnd@arndb.de, bp@alien8.de, brijesh.singh@amd.com,
        dan.j.williams@intel.com, dave.hansen@linux.intel.com,
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        peterz@infradead.org, rostedt@goodmis.org,
        sathyanarayanan.kuppuswamy@linux.intel.com, seanjc@google.com,
        tglx@linutronix.de, tony.luck@intel.com, wei.liu@kernel.org,
        x86@kernel.org, mikelley@microsoft.com,
        linux-kernel@vger.kernel.org, Tianyu.Lan@microsoft.com
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From:   Dave Hansen <dave.hansen@intel.com>
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On 5/23/23 15:37, kirill.shutemov@linux.intel.com wrote:
>> How does this work with load_unaligned_zeropad()?  Couldn't it be
>> running around poking at one of these vmalloc()'d pages via the direct
>> map during a shared->private conversion before the page has been accepted?
> Alias processing in __change_page_attr_set_clr() will change direct
> mapping if you call it on vmalloc()ed memory. I think we are safe wrt
> load_unaligned_zeropad() here.

We're *eventually* OK:

>         /* Notify hypervisor that we are about to set/clr encryption attribute. */
>         x86_platform.guest.enc_status_change_prepare(addr, numpages, enc);
> 
>         ret = __change_page_attr_set_clr(&cpa, 1);

But what about in the middle between enc_status_change_prepare() and
__change_page_attr_set_clr()?  Don't the direct map and the
shared/private status of the page diverge in there?