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AJvYcCXtPGBUAGSmkYrfXBI0mdn9KhlT+WmO5EXxLL/Oz9HQ5kwTt/uoI2R14OJ1prEaYn9zloVKwTtvRmJEaNL95xtp2JM=@vger.kernel.org X-Gm-Message-State: AOJu0Yxov+gVuUEU7Ko5lGB8E/ZZVu+U/EwGMwb2x16/3bX/P+q/xE8p ed3pDoqMYnrw/flUwpssBz/0iVRZf1vg5WteUwX6zzfPcl8tcdJpWm9XiAkQieGqKrGQCNBrXKn BPg== X-Google-Smtp-Source: AGHT+IHuJhugLoOALKL+bBHU8dYmihquWXJgCeAnlxsMLGlSruW3vsfZyq9aR+pdE7QTJi2WhpCLVWh7qaw= X-Received: from pjbpd10.prod.google.com ([2002:a17:90b:1dca:b0:2fa:15aa:4d1e]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:1d46:b0:2f5:88bb:118 with SMTP id 98e67ed59e1d1-2febabf19bemr1619311a91.22.1740700025364; Thu, 27 Feb 2025 15:47:05 -0800 (PST) Date: Thu, 27 Feb 2025 15:47:03 -0800 In-Reply-To: <7f2b25c9-c92b-4b0a-bfd9-dda8b0b7a244@amazon.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <6eddd049-7c7a-406d-b763-78fa1e7d921b@amazon.com> <946fc0f5-4306-4aa9-9b63-f7ccbaff8003@amazon.com> <7f2b25c9-c92b-4b0a-bfd9-dda8b0b7a244@amazon.com> Message-ID: Subject: Re: [RFC PATCH 0/6] KVM: x86: async PF user From: Sean Christopherson To: Nikita Kalyazin Cc: pbonzini@redhat.com, corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, jthoughton@google.com, david@redhat.com, peterx@redhat.com, oleg@redhat.com, vkuznets@redhat.com, gshan@redhat.com, graf@amazon.de, jgowans@amazon.com, roypat@amazon.co.uk, derekmn@amazon.com, nsaenz@amazon.es, xmarcalx@amazon.com Content-Type: text/plain; charset="us-ascii" On Thu, Feb 27, 2025, Nikita Kalyazin wrote: > On 27/02/2025 16:44, Sean Christopherson wrote: > > When it comes to uAPI, I want to try and avoid statements along the lines of > > "IF 'x' holds true, then 'y' SHOULDN'T be a problem". If this didn't impact uAPI, > > I wouldn't care as much, i.e. I'd be much more willing iterate as needed. > > > > I'm not saying we should go straight for a complex implementation. Quite the > > opposite. But I do want us to consider the possible ramifications of using a > > single bit for all userfaults, so that we can at least try to design something > > that is extensible and won't be a pain to maintain. > > So you would've liked more the "two-bit per gfn" approach as in: provide 2 > interception points, for sync and async exits, with the former chosen by > userspace when it "knows" that the content is already in memory? No, all I'm saying is I want people think about what the future will look like, to minimize the chances of ending up with a mess.