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[35.185.214.157]) by smtp.gmail.com with ESMTPSA id on6sm72382pjb.47.2021.11.15.10.44.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 15 Nov 2021 10:44:52 -0800 (PST) Date: Mon, 15 Nov 2021 18:44:48 +0000 From: Sean Christopherson To: Brijesh Singh Cc: Borislav Petkov , Dave Hansen , Peter Gonda , x86@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-coco@lists.linux.dev, linux-mm@kvack.org, linux-crypto@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Joerg Roedel , Tom Lendacky , "H. Peter Anvin" , Ard Biesheuvel , Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Andy Lutomirski , Dave Hansen , Sergio Lopez , Peter Zijlstra , Srinivas Pandruvada , David Rientjes , Dov Murik , Tobin Feldman-Fitzthum , Michael Roth , Vlastimil Babka , "Kirill A . Shutemov" , Andi Kleen , tony.luck@intel.com, marcorr@google.com, sathyanarayanan.kuppuswamy@linux.intel.com Subject: Re: [PATCH Part2 v5 00/45] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support Message-ID: References: <20210820155918.7518-1-brijesh.singh@amd.com> <061ccd49-3b9f-d603-bafd-61a067c3f6fa@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 129EE5093077 X-Stat-Signature: knjrxwzjnso1s8wg8zwjd8wp7e4a3iet Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=b2wJRkAt; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf05.hostedemail.com: domain of seanjc@google.com designates 209.85.215.172 as permitted sender) smtp.mailfrom=seanjc@google.com X-HE-Tag: 1637001868-789563 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Nov 15, 2021, Brijesh Singh wrote: > > On 11/12/21 2:37 PM, Sean Christopherson wrote: > > This is the direction KVM TDX support is headed, though it's obviously still a WIP. > > > > Just curious, in this approach, how do you propose handling the host > kexec/kdump? If a kexec/kdump occurs while the VM is still active, the new > kernel will encounter the #PF (RMP violation) because some pages are still > marked 'private' in the RMP table. There are two basic options: a) eagerly purge the RMP or b) lazily fixup the RMP on #PF. Either approach can be made to work. I'm not opposed to fixing up the RMP on #PF in the kexec/kdump case, I'm opposed to blindly updating the RMP on _all_ RMP #PFs, i.e. the kernel should modify the RMP if and only if it knows that doing so is correct. E.g. a naive lazy-fixup solution would be to track which pages have been sanitized and adjust the RMP on #PF to a page that hasn't yet been sanitized.