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Wed, 24 Jul 2024 10:31:08 -0700 (PDT) X-Google-Smtp-Source: AGHT+IH+CTFF1dcJgxOzaL+UHgEN1b5oHLlWnYL5mpea++gifRuH4tZsqextQloB8b501afv5ky36g== X-Received: by 2002:a05:6214:124e:b0:6b5:9439:f048 with SMTP id 6a1803df08f44-6bb3c9e18b6mr4147026d6.19.1721842268119; Wed, 24 Jul 2024 10:31:08 -0700 (PDT) Received: from starship ([2607:fea8:fc01:7b7f:6adb:55ff:feaa:b156]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6b7b29a0364sm57156046d6.119.2024.07.24.10.31.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Jul 2024 10:31:07 -0700 (PDT) Message-ID: <203755ada291a1366df78c75c57585aff06f30c6.camel@redhat.com> Subject: Re: [PATCH v2 11/49] KVM: x86: Disallow KVM_CAP_X86_DISABLE_EXITS after vCPU creation From: Maxim Levitsky To: Sean Christopherson 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 Date: Wed, 24 Jul 2024 13:31:06 -0400 In-Reply-To: References: <20240517173926.965351-1-seanjc@google.com> <20240517173926.965351-12-seanjc@google.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.5 (3.36.5-2.fc32) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 7bit 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? Best regards, Maxim Levitsky