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([2001:b07:6468:f312:4013:e920:9388:c3ff]) by smtp.gmail.com with ESMTPSA id b8sm99851723wmh.46.2019.08.02.01.30.10 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Fri, 02 Aug 2019 01:30:11 -0700 (PDT) Subject: Re: [RFC PATCH v2 08/19] RISC-V: KVM: Implement VCPU world-switch To: Anup Patel , Palmer Dabbelt , Paul Walmsley , Radim K References: <20190802074620.115029-1-anup.patel@wdc.com> <20190802074620.115029-9-anup.patel@wdc.com> From: Paolo Bonzini Openpgp: preference=signencrypt Message-ID: <72d8efbf-ec62-ab1e-68bf-e0c5f0bc256e@redhat.com> Date: Fri, 2 Aug 2019 10:30:10 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190802074620.115029-9-anup.patel@wdc.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190802_013013_485242_FFEB48FE X-CRM114-Status: UNSURE ( 8.86 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Damien Le Moal , "kvm@vger.kernel.org" , Anup Patel , Daniel Lezcano , "linux-kernel@vger.kernel.org" , Christoph Hellwig , Atish Patra , Alistair Francis , Thomas Gleixner , "linux-riscv@lists.infradead.org" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+infradead-linux-riscv=archiver.kernel.org@lists.infradead.org On 02/08/19 09:47, Anup Patel wrote: > + /* Save Host SSTATUS, HSTATUS, SCRATCH and STVEC */ > + csrr t0, CSR_SSTATUS > + REG_S t0, (KVM_ARCH_HOST_SSTATUS)(a0) > + csrr t1, CSR_HSTATUS > + REG_S t1, (KVM_ARCH_HOST_HSTATUS)(a0) > + csrr t2, CSR_SSCRATCH > + REG_S t2, (KVM_ARCH_HOST_SSCRATCH)(a0) > + csrr t3, CSR_STVEC > + REG_S t3, (KVM_ARCH_HOST_STVEC)(a0) > + A possible optimization: if these cannot change while Linux runs (I am thinking especially of STVEC and HSTATUS, but perhaps SSCRATCH can be saved on kvm_arch_vcpu_load too) you can avoid the csrr and store. Paolo _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv