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X-CSE-ConnectionGUID: psR+SW42RI+/gkG1He2OVg== X-CSE-MsgGUID: uVHKB8ReSuOdec1OulOaaA== X-IronPort-AV: E=McAfee;i="6700,10204,11222"; a="30216961" X-IronPort-AV: E=Sophos;i="6.11,199,1725346800"; d="scan'208";a="30216961" Received: from orviesa008.jf.intel.com ([10.64.159.148]) by orvoesa113.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Nov 2024 11:43:57 -0700 X-CSE-ConnectionGUID: nItOh5W8SBua+HcT4OK75w== X-CSE-MsgGUID: Rqmuf4uZTza2bSiqESaTiw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.11,250,1725346800"; d="scan'208";a="83866016" Received: from ccbilbre-mobl3.amr.corp.intel.com (HELO [10.124.220.146]) ([10.124.220.146]) by orviesa008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Nov 2024 11:43:54 -0700 Message-ID: Date: Fri, 1 Nov 2024 11:43:52 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v3 0/6] Direct Map Removal for guest_memfd To: "Manwaring, Derek" Cc: ackerleytng@google.com, agordeev@linux.ibm.com, aou@eecs.berkeley.edu, borntraeger@linux.ibm.com, bp@alien8.de, canellac@amazon.at, catalin.marinas@arm.com, chenhuacai@kernel.org, corbet@lwn.net, dave.hansen@linux.intel.com, david@redhat.com, elena.reshetova@intel.com, gerald.schaefer@linux.ibm.com, gor@linux.ibm.com, graf@amazon.com, hca@linux.ibm.com, hpa@zytor.com, jgowans@amazon.com, jthoughton@google.com, kalyazin@amazon.com, kernel@xen0n.name, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-trace-kernel@vger.kernel.org, loongarch@lists.linux.dev, luto@kernel.org, mathieu.desnoyers@efficios.com, mhiramat@kernel.org, mingo@redhat.com, mlipp@amazon.at, palmer@dabbelt.com, paul.walmsley@sifive.com, pbonzini@redhat.com, peterz@infradead.org, quic_eberman@quicinc.com, rostedt@goodmis.org, roypat@amazon.co.uk, rppt@kernel.org, seanjc@google.com, shuah@kernel.org, svens@linux.ibm.com, tabba@google.com, tglx@linutronix.de, vannapurve@google.com, will@kernel.org, x86@kernel.org, xmarcalx@amazon.com References: <51fe5ad1-7057-4d43-b92c-580d187d2aeb@intel.com> <37fbfc65-b145-4a22-a48c-1921204d5635@amazon.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: A2FD24001D X-Stat-Signature: bmswpqhpbme1dqgz7tktsjjsibh8g3j8 X-Rspam-User: X-Rspamd-Server: rspam05 X-HE-Tag: 1730486603-550361 X-HE-Meta: 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 F6cZdPNi oSSr4SEnPLTlV8gkOsNsmghslOMJBuoeEAdyb0VuKvVYoLh5sSHN+kqRPD9u7OgtEEbF65Jm853JbCYe56pw04ZKs10Au0fbTgy7ewBrhTvAEKt5uRgDR3tgqXrc+m4+sxQi753No4k0tTvzOel9C+3xgRFvJh7OHDKYYMGfj/Le6IVJhQeIBDbEZ5H22VPn7crD3fr7ZlHlrMqeUgNpunx+vXprLlaviotwDAXkDIjv8Bs/LJI7BxHsKw0b4T+6Hu9Bbg/vnJc62ILF5ykj3TBWeAg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.019950, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 11/1/24 11:31, Manwaring, Derek wrote: >>>From that standpoint I'm still tempted to turn the question around a bit > for the host kernel's perspective. Like if the host kernel should not > (and indeed cannot with TDX controls in place) access guest private > memory, why not remove it from the direct map? Pretend that the machine check warts aren't there. It costs performance and complexity, for an only theoretical gain. This is especially true for a VMM that's not doing a just doing confidential guests. You fracture the direct map to pieces forever (for now).