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([2001:b07:6468:f312:5e2c:eb9a:a8b6:fd3e]) by smtp.gmail.com with ESMTPSA id pw11sm1943513ejb.88.2021.05.04.14.12.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 04 May 2021 14:12:14 -0700 (PDT) Subject: Re: [PATCH] KVM/VMX: Invoke NMI non-IST entry instead of IST entry To: Maxim Levitsky , Thomas Gleixner , Lai Jiangshan , linux-kernel@vger.kernel.org Cc: Lai Jiangshan , Sean Christopherson , Steven Rostedt , Andi Kleen , Andy Lutomirski , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Josh Poimboeuf , Uros Bizjak , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Alexandre Chartre , Juergen Gross , Joerg Roedel , Jian Cai References: <20210426230949.3561-1-jiangshanlai@gmail.com> <20210426230949.3561-3-jiangshanlai@gmail.com> <87bl9rk23k.ffs@nanos.tec.linutronix.de> <878s4vk1l9.ffs@nanos.tec.linutronix.de> <875yzzjxth.ffs@nanos.tec.linutronix.de> <87wnseis8v.ffs@nanos.tec.linutronix.de> <87r1imi8i1.ffs@nanos.tec.linutronix.de> <44e20d7cdbf0ffdb7d9dce7d480f86a6f14d16c1.camel@redhat.com> From: Paolo Bonzini Message-ID: Date: Tue, 4 May 2021 23:12:12 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <44e20d7cdbf0ffdb7d9dce7d480f86a6f14d16c1.camel@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/05/21 23:05, Maxim Levitsky wrote: > Does this mean that we still rely on hardware NMI masking to be activated? No, the NMI code already handles reentrancy at both the assembly and C levels. > Or in other words, that is we still can't have an IRET between VM exit and > the entry to the NMI handler? No, because NMIs are not masked on VM exit. This in fact makes things potentially messy; unlike with AMD's CLGI/STGI, only MSRs and other things that Intel thought can be restored atomically with the VM exit. Paolo