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([2001:b07:6468:f312:48f9:bea:a04c:3dfe]) by smtp.googlemail.com with ESMTPSA id a10sm12136566wmq.27.2021.12.17.06.51.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 17 Dec 2021 06:51:19 -0800 (PST) Message-ID: Date: Fri, 17 Dec 2021 15:51:14 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: Possible nohz-full/RCU issue in arm64 KVM Content-Language: en-US To: Mark Rutland , Nicolas Saenz Julienne Cc: paulmck , maz , frederic , linux-kernel , rcu , Thomas Gleixner , Will Deacon , kvmarm@lists.cs.columbia.edu, linux-arm-kernel , "kvm-riscv@lists.infradead.org" , Anup Patel References: From: Paolo Bonzini In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211217_065122_713843_B70B51CB X-CRM114-Status: GOOD ( 10.32 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 12/17/21 14:21, Mark Rutland wrote: > I'm not immediately sure what we*should* do here. What does x86 do for an IRQ > taken from a guest mode? I couldn't spot any handling of that case, but I'm not > familiar enough with the x86 exception model to know if I'm looking in the > right place. ARM is missing something like commit 160457140187 ("KVM: x86: Defer vtime accounting 'til after IRQ handling", 2021-05-05). With that change, it would be possible to move guest_exit() in the irq-disabled region without breaking time accounting. RISC-V has the same issue and it would be fixed in the same way, so let's Cc Anup too. Paolo _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel