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[34.168.104.7]) by smtp.gmail.com with ESMTPSA id e20-20020a63e014000000b0045ff216a0casm1080329pgh.3.2022.11.03.10.53.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Nov 2022 10:53:35 -0700 (PDT) Date: Thu, 3 Nov 2022 17:53:31 +0000 From: Sean Christopherson To: Paolo Bonzini Subject: Re: [PATCH 39/44] KVM: Drop kvm_count_lock and instead protect kvm_usage_count with kvm_lock Message-ID: References: <20221102231911.3107438-1-seanjc@google.com> <20221102231911.3107438-40-seanjc@google.com> <7b6ce80e-7f1f-11cd-8bde-8d8fa9fd7e1d@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <7b6ce80e-7f1f-11cd-8bde-8d8fa9fd7e1d@redhat.com> Cc: Matthew Rosato , David Hildenbrand , Yuan Yao , Paul Walmsley , linux-kernel@vger.kernel.org, Michael Ellerman , linux-riscv@lists.infradead.org, Claudio Imbrenda , kvmarm@lists.cs.columbia.edu, linux-s390@vger.kernel.org, Janosch Frank , Marc Zyngier , Huacai Chen , Aleksandar Markovic , Christian Borntraeger , Chao Gao , Eric Farman , Albert Ou , kvm@vger.kernel.org, Atish Patra , kvmarm@lists.linux.dev, Thomas Gleixner , linux-arm-kernel@lists.infradead.org, Isaku Yamahata , Fabiano Rosas , linux-mips@vger.kernel.org, Palmer Dabbelt , kvm-riscv@lists.infradead.org, Vitaly Kuznetsov , linuxppc-dev@lists.ozlabs.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Thu, Nov 03, 2022, Paolo Bonzini wrote: > On 11/3/22 00:19, Sean Christopherson wrote: > > +- kvm_lock is taken outside kvm->mmu_lock > > Not surprising since one is a mutex and one is an rwlock. :) Heh, Signed-off-by: Captain Obvious > You can drop this hunk as well as the "Opportunistically update KVM's locking > documentation" sentence in the commit message. Will do. > > - vcpu->mutex is taken outside kvm->arch.hyperv.hv_lock > > - kvm->arch.mmu_lock is an rwlock. kvm->arch.tdp_mmu_pages_lock and > > @@ -216,15 +220,11 @@ time it will be set using the Dirty tracking mechanism described above. > > :Type: mutex > > :Arch: any > > :Protects: - vm_list > > - > > -``kvm_count_lock`` > > -^^^^^^^^^^^^^^^^^^ > > - > > -:Type: raw_spinlock_t > > -:Arch: any > > -:Protects: - hardware virtualization enable/disable > > -:Comment: 'raw' because hardware enabling/disabling must be atomic /wrt > > - migration. > > + - kvm_usage_count > > + - hardware virtualization enable/disable > > + - module probing (x86 only) > > What do you mean exactly by "module probing"? Is it anything else than what > is serialized by vendor_module_lock? Ooh, I forgot to update this patch after switching to vendor_module_lock. I added the above after fixing the first deadlock between kvm_lock and cpu_hotplug_lock, but later gave up on trying to use kvm_lock after deadlock #2, which is when I when I realized piggybacking kvm_lock was going to be a maintainance nightmare due. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f179.google.com (mail-pg1-f179.google.com [209.85.215.179]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 45EC763A0 for ; Thu, 3 Nov 2022 17:53:36 +0000 (UTC) Received: by mail-pg1-f179.google.com with SMTP id f63so2333909pgc.2 for ; Thu, 03 Nov 2022 10:53:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=3tXwq1v6tJCedr2VtV8ELYd8BpIXTKwmGjuY8weIxs8=; b=gjqnoLy192oz/Zxvag+BlBreQGGSfkeJOmpmCEx7rtJpm2GzAgZsoDzOerCZhLAwiY s4s7ScvfoZl8zwg6HI1Ymb7QpOkn2NxzwKs5NTcMl1wbeFQ/hmv3VmCXwSollG4iohk8 ZfCLF4UOQot0TZFoB2ZSgy0wzT2PFfm47J97NCOCE8O1C25eIzJzc1jTDAryWTakKtb6 +QR4ykcFsYtONZVST62uH0g9I4NSfzwB8k/a9JLQz8I+tNs7JhVckzNuFRTBv1+mgFsk IdkM799qrsruF4xx+MeYDtb4Sd8Y4cxbHh++70LJo94wIuv8aLLKYeYlUVyl7mOC3bBK Ww4w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=3tXwq1v6tJCedr2VtV8ELYd8BpIXTKwmGjuY8weIxs8=; b=N/ixmfg+E77R2vC5k7aCTa8G55MyAiKIjVnXiELx+6q6OBlyoKz1c7Abnmo1d99QP0 H20ENMru+h+1/0q05IVdtXvBCC1HKBPxwkYd+x0L7xzdD1AhXslh9yzEmhnIzCbfJbM5 Tn2Z7dhM5Mf8isvWali059BhF2Ce7HAIku/syLqQhTfFrSZv+sfi3n1ztH4TlvlQfIZJ wCZtiYo6HOMUa9UIlw6u7koqC+UDhX8LarE4vHDs3Bwg7qNS6aPjbxN6cX7eBrWb/gE7 PSjizkivCIEWDcP8bubnksNORw9ZTsXMlVJtZlBgVHihKFzqupyyoZcxaJQDh8Bsl1yh rT0g== X-Gm-Message-State: ACrzQf32950DBrmX4tL0Mj9Rq1UztoFZ4P3FiWcBzAp0kBqNYAfb8XQD U+6Psd5RsMntIv72h+G23gLHKg== X-Google-Smtp-Source: AMsMyM5pSkjZTiut6RFho0StQnuo7qAiklz26C63x768BJpOt4UV7sKT8fcspUYyR/B7P1xdFXKPhA== X-Received: by 2002:a05:6a00:999:b0:56c:3d0d:96fe with SMTP id u25-20020a056a00099900b0056c3d0d96femr31657100pfg.12.1667498015565; Thu, 03 Nov 2022 10:53:35 -0700 (PDT) Received: from google.com (7.104.168.34.bc.googleusercontent.com. [34.168.104.7]) by smtp.gmail.com with ESMTPSA id e20-20020a63e014000000b0045ff216a0casm1080329pgh.3.2022.11.03.10.53.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Nov 2022 10:53:35 -0700 (PDT) Date: Thu, 3 Nov 2022 17:53:31 +0000 From: Sean Christopherson To: Paolo Bonzini Cc: Marc Zyngier , Huacai Chen , Aleksandar Markovic , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Matthew Rosato , Eric Farman , Vitaly Kuznetsov , James Morse , Alexandru Elisei , Suzuki K Poulose , Oliver Upton , Atish Patra , David Hildenbrand , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Isaku Yamahata , Fabiano Rosas , Michael Ellerman , Chao Gao , Thomas Gleixner , Yuan Yao Subject: Re: [PATCH 39/44] KVM: Drop kvm_count_lock and instead protect kvm_usage_count with kvm_lock Message-ID: References: <20221102231911.3107438-1-seanjc@google.com> <20221102231911.3107438-40-seanjc@google.com> <7b6ce80e-7f1f-11cd-8bde-8d8fa9fd7e1d@redhat.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7b6ce80e-7f1f-11cd-8bde-8d8fa9fd7e1d@redhat.com> Message-ID: <20221103175331.lSOkwvxFKRGilk-JAki1k3tJ40fddBJZChsN4qFOg68@z> On Thu, Nov 03, 2022, Paolo Bonzini wrote: > On 11/3/22 00:19, Sean Christopherson wrote: > > +- kvm_lock is taken outside kvm->mmu_lock > > Not surprising since one is a mutex and one is an rwlock. :) Heh, Signed-off-by: Captain Obvious > You can drop this hunk as well as the "Opportunistically update KVM's locking > documentation" sentence in the commit message. Will do. > > - vcpu->mutex is taken outside kvm->arch.hyperv.hv_lock > > - kvm->arch.mmu_lock is an rwlock. kvm->arch.tdp_mmu_pages_lock and > > @@ -216,15 +220,11 @@ time it will be set using the Dirty tracking mechanism described above. > > :Type: mutex > > :Arch: any > > :Protects: - vm_list > > - > > -``kvm_count_lock`` > > -^^^^^^^^^^^^^^^^^^ > > - > > -:Type: raw_spinlock_t > > -:Arch: any > > -:Protects: - hardware virtualization enable/disable > > -:Comment: 'raw' because hardware enabling/disabling must be atomic /wrt > > - migration. > > + - kvm_usage_count > > + - hardware virtualization enable/disable > > + - module probing (x86 only) > > What do you mean exactly by "module probing"? Is it anything else than what > is serialized by vendor_module_lock? Ooh, I forgot to update this patch after switching to vendor_module_lock. I added the above after fixing the first deadlock between kvm_lock and cpu_hotplug_lock, but later gave up on trying to use kvm_lock after deadlock #2, which is when I when I realized piggybacking kvm_lock was going to be a maintainance nightmare due.