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[34.168.104.7]) by smtp.gmail.com with ESMTPSA id e88-20020a17090a6fe100b00205d85cfb30sm4956147pjk.20.2022.10.07.11.18.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 07 Oct 2022 11:18:06 -0700 (PDT) Date: Fri, 7 Oct 2022 18:18:02 +0000 From: Sean Christopherson To: Christian Borntraeger Cc: Shivam Kumar , pbonzini@redhat.com, maz@kernel.org, james.morse@arm.com, david@redhat.com, Claudio Imbrenda , Janosch Frank , kvm@vger.kernel.org, Shaju Abraham , Manish Mishra , Anurag Madnawat , Heiko Carstens , Sven Schnelle , Vasily Gorbik , Alexander Gordeev Subject: Re: [PATCH v6 1/5] KVM: Implement dirty quota-based throttling of vcpus Message-ID: References: <20220915101049.187325-1-shivam.kumar1@nutanix.com> <20220915101049.187325-2-shivam.kumar1@nutanix.com> <52ad1240-1201-259a-80d0-6e05da561a7f@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <52ad1240-1201-259a-80d0-6e05da561a7f@linux.ibm.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Sep 15, 2022, Christian Borntraeger wrote: > Am 15.09.22 um 15:21 schrieb Christian Borntraeger: > > I am wondering if this will work on s390. On s390  we only call > > mark_page_dirty_in_slot for the kvm_read/write functions but not > > for those done by the guest on fault. We do account those lazily in > > kvm_arch_sync_dirty_log (like x96 in the past). > > > > I think we need to rework the page fault handling on s390 to actually make > use of this. This has to happen anyway somewhen (as indicated by the guest > enter/exit rework from Mark). Right now we handle KVM page faults directly > in the normal system fault handler. It seems we need to make a side turn > into KVM for page faults on guests in the long run. s390's page table management came up in conversation at KVM Forum in the context of a common MMU (or MMUs)[*]. If/when we get an MMU that supports multiple architectures, that would be a perfect opportunity for s390 to switch. I don't know that it'll be feasible to make a common MMU support s390 from the get-go, but at the very least we can keep y'all in the loop and not make it unnecessarily difficult to support s390. [*] https://kvmforum2022.sched.com/event/15jJk