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Date: Mon, 29 Apr 2024 15:47:25 +0200
From: Greg KH <gregkh@linuxfoundation.org>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: stable@vger.kernel.org, Chris Oo <cho@microsoft.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Rick Edgecombe <rick.p.edgecombe@intel.com>,
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>,
	Tom Lendacky <thomas.lendacky@amd.com>
Subject: Re: [PATCH 6.6.y] x86/tdx: Preserve shared bit on mprotect()
Message-ID: <2024042902-grope-easing-82a1@gregkh>
References: <2024042908-modular-case-bbd4@gregkh>
 <20240429122700.4100457-1-kirill.shutemov@linux.intel.com>
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In-Reply-To: <20240429122700.4100457-1-kirill.shutemov@linux.intel.com>

On Mon, Apr 29, 2024 at 03:27:00PM +0300, Kirill A. Shutemov wrote:
> The TDX guest platform takes one bit from the physical address to
> indicate if the page is shared (accessible by VMM). This bit is not part
> of the physical_mask and is not preserved during mprotect(). As a
> result, the 'shared' bit is lost during mprotect() on shared mappings.
> 
> _COMMON_PAGE_CHG_MASK specifies which PTE bits need to be preserved
> during modification. AMD includes 'sme_me_mask' in the define to
> preserve the 'encrypt' bit.
> 
> To cover both Intel and AMD cases, include 'cc_mask' in
> _COMMON_PAGE_CHG_MASK instead of 'sme_me_mask'.
> 
> Reported-and-tested-by: Chris Oo <cho@microsoft.com>
> 
> Fixes: 41394e33f3a0 ("x86/tdx: Extend the confidential computing API to support TDX guests")
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
> Cc: stable@vger.kernel.org
> Link: https://lore.kernel.org/all/20240424082035.4092071-1-kirill.shutemov%40linux.intel.com
> (cherry picked from commit a0a8d15a798be4b8f20aca2ba91bf6b688c6a640)
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

Both backports now queued up, thanks.

greg k-h