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Date: Tue, 17 Aug 2021 22:44:48 +0200
From: Borislav Petkov <bp@alien8.de>
To: Brijesh Singh <brijesh.singh@amd.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org,
	linux-coco@lists.linux.dev, linux-mm@kvack.org,
	linux-crypto@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Joerg Roedel <jroedel@suse.de>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	"H. Peter Anvin" <hpa@zytor.com>, Ard Biesheuvel <ardb@kernel.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <seanjc@google.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>,
	Andy Lutomirski <luto@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Sergio Lopez <slp@redhat.com>, Peter Gonda <pgonda@google.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
	David Rientjes <rientjes@google.com>,
	Dov Murik <dovmurik@linux.ibm.com>,
	Tobin Feldman-Fitzthum <tobin@ibm.com>,
	Michael Roth <michael.roth@amd.com>,
	Vlastimil Babka <vbabka@suse.cz>, tony.luck@intel.com,
	npmccallum@redhat.com, brijesh.ksingh@gmail.com
Subject: Re: [PATCH Part1 RFC v4 15/36] x86/mm: Add support to validate
 memory when changing C-bit
Message-ID: <YRwfwCo4gwjWMbD0@zn.tnic>
References: <20210707181506.30489-1-brijesh.singh@amd.com>
 <20210707181506.30489-16-brijesh.singh@amd.com>
 <YRvxZtLkVNda9xwX@zn.tnic>
 <d9aabcb8-9db2-838c-74c7-c0e759257d3f@amd.com>
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In-Reply-To: <d9aabcb8-9db2-838c-74c7-c0e759257d3f@amd.com>

On Tue, Aug 17, 2021 at 03:34:41PM -0500, Brijesh Singh wrote:
> I am not seeing any strong reason to sanity check the reserved bit in the
> psc_entry. The fields in the psc_entry are input from guest to the
> hypervisor. The hypervisor cannot trick a guest by changing anything in the
> psc_entry because guest does not read the hypervisor filled value. I am okay
> with the psc_hdr because we need to read the current and end entry after the
> PSC completes to determine whether it was successful and sanity checking PSC
> header makes much more sense. Let me know if you are okay with it ?

Ok, fair enough.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette