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AJvYcCV2SET+8U7X8Oj6WCC6GkaRAvs8VxrV7ecjgXzRaFCegfCwP1LCadYvAGE7NZS0iZWlQs6kK3k4XCZ3GGzBGAgXDrUUpyq7bHTcL2lq X-Gm-Message-State: AOJu0YxbMnJSKTSqRATF971iyUQqR5j2CQito0kIBTfpe0mmHyAyZI5L wN6EtvMH1hDGKsBcmifL7YTXkgIxjMS8XqP+QfvRnRaaTj9sCRY1tJaJup2lkiCZwjY7PCTeiL3 8hA== X-Google-Smtp-Source: AGHT+IF7zMLJuphWTLkC+nevqZK7ixm1Yql8ScY0ucZbb06AZigHjX0DHxi+uHSzp+K6lZveDOipKORXTpI= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a17:90a:1786:b0:2c9:967d:94a4 with SMTP id 98e67ed59e1d1-2cf2ede0296mr5153a91.5.1721930874905; Thu, 25 Jul 2024 11:07:54 -0700 (PDT) Date: Thu, 25 Jul 2024 11:07:53 -0700 In-Reply-To: <203755ada291a1366df78c75c57585aff06f30c6.camel@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240517173926.965351-1-seanjc@google.com> <20240517173926.965351-12-seanjc@google.com> <203755ada291a1366df78c75c57585aff06f30c6.camel@redhat.com> Message-ID: Subject: Re: [PATCH v2 11/49] KVM: x86: Disallow KVM_CAP_X86_DISABLE_EXITS after vCPU creation From: Sean Christopherson To: Maxim Levitsky Cc: Paolo Bonzini , Vitaly Kuznetsov , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Hou Wenlong , Kechen Lu , Oliver Upton , Binbin Wu , Yang Weijiang , Robert Hoo Content-Type: text/plain; charset="us-ascii" On Wed, Jul 24, 2024, Maxim Levitsky wrote: > On Mon, 2024-07-08 at 19:43 +0000, Sean Christopherson wrote: > > On Thu, Jul 04, 2024, Maxim Levitsky wrote: > > > On Fri, 2024-05-17 at 10:38 -0700, Sean Christopherson wrote: > > > > Reject KVM_CAP_X86_DISABLE_EXITS if vCPUs have been created, as disabling > > > > PAUSE/MWAIT/HLT exits after vCPUs have been created is broken and useless, > > > > e.g. except for PAUSE on SVM, the relevant intercepts aren't updated after > > > > vCPU creation. vCPUs may also end up with an inconsistent configuration > > > > if exits are disabled between creation of multiple vCPUs. > > > > > > Hi, > > > > > > I am not sure that PAUSE intercepts are updated either, I wasn't able to find a code > > > that does this. > > > > > > I agree with this change, but note that there was some talk on the mailing > > > list to allow to selectively disable VM exits (e.g PAUSE, MWAIT, ...) only on > > > some vCPUs, based on the claim that some vCPUs might run RT tasks, while some > > > might be housekeeping. I haven't followed those discussions closely. > > > > This change is actually pulled from that series[*]. IIRC, v1 of that series > > didn't close the VM-scoped hole, and the overall code was much more complex as > > a result. > > > > [*] https://lore.kernel.org/all/20230121020738.2973-2-kechenl@nvidia.com > > > > Hi, > Thanks for the pointer, I searched for this patch series in many places but I > couldn't find it. > Any idea what happened with this patch series btw? Nope. IIRC, v6 was close to being ready and only had a few cosmetic issues, but the author never posted a v7.