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([2001:b07:6468:f312:9520:22e6:6416:5c36]) by smtp.gmail.com with ESMTPSA id s12sm14065554wrn.90.2019.09.23.04.12.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 23 Sep 2019 04:12:20 -0700 (PDT) Subject: Re: [PATCH v7 10/21] RISC-V: KVM: Handle MMIO exits for VCPU To: Anup Patel , Palmer Dabbelt , Paul Walmsley , Radim K References: <20190904161245.111924-1-anup.patel@wdc.com> <20190904161245.111924-12-anup.patel@wdc.com> From: Paolo Bonzini Message-ID: <8c44ac8a-3fdc-b9dd-1815-06e86cb73047@redhat.com> Date: Mon, 23 Sep 2019 13:12:17 +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: <20190904161245.111924-12-anup.patel@wdc.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190923_041224_240099_C4A6BC67 X-CRM114-Status: GOOD ( 15.69 ) 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 , Alexander Graf , 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 04/09/19 18:15, Anup Patel wrote: > + unsigned long guest_sstatus = > + vcpu->arch.guest_context.sstatus | SR_MXR; > + unsigned long guest_hstatus = > + vcpu->arch.guest_context.hstatus | HSTATUS_SPRV; > + unsigned long guest_vsstatus, old_stvec, tmp; > + > + guest_sstatus = csr_swap(CSR_SSTATUS, guest_sstatus); > + old_stvec = csr_swap(CSR_STVEC, (ulong)&__kvm_riscv_unpriv_trap); > + > + if (read_insn) { > + guest_vsstatus = csr_read_set(CSR_VSSTATUS, SR_MXR); Is this needed? IIUC SSTATUS.MXR encompasses a wider set of permissions: The HS-level MXR bit makes any executable page readable. {\tt vsstatus}.MXR makes readable those pages marked executable at the VS translation level, but only if readable at the guest-physical translation level. So it should be enough to set SSTATUS.MXR=1 I think. But you also shouldn't set SSTATUS.MXR=1 in the !read_insn case. Also, you can drop the irq save/restore (which is already a save/restore of SSTATUS) since you already write 0 to SSTATUS.SIE in your csr_swap. Perhaps add a BUG_ON(guest_sstatus & SR_SIE) before the csr_swap? > + asm volatile ("\n" > + "csrrw %[hstatus], " STR(CSR_HSTATUS) ", %[hstatus]\n" > + "li %[tilen], 4\n" > + "li %[tscause], 0\n" > + "lhu %[val], (%[addr])\n" > + "andi %[tmp], %[val], 3\n" > + "addi %[tmp], %[tmp], -3\n" > + "bne %[tmp], zero, 2f\n" > + "lhu %[tmp], 2(%[addr])\n" > + "sll %[tmp], %[tmp], 16\n" > + "add %[val], %[val], %[tmp]\n" > + "2: csrw " STR(CSR_HSTATUS) ", %[hstatus]" > + : [hstatus] "+&r"(guest_hstatus), [val] "=&r" (val), > + [tmp] "=&r" (tmp), [tilen] "+&r" (tilen), > + [tscause] "+&r" (tscause) > + : [addr] "r" (addr)); > + csr_write(CSR_VSSTATUS, guest_vsstatus); > > +#ifndef CONFIG_RISCV_ISA_C > + "li %[tilen], 4\n" > +#else > + "li %[tilen], 2\n" > +#endif Can you use an assembler directive to force using a non-compressed format for ld and lw? This would get rid of tilen, which is costing 6 bytes (if I did the RVC math right) in order to save two. :) Paolo > + "li %[tscause], 0\n" > +#ifdef CONFIG_64BIT > + "ld %[val], (%[addr])\n" > +#else > + "lw %[val], (%[addr])\n" > +#endif _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv