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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id u6sm10083891ejn.14.2021.05.18.02.18.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 May 2021 02:19:00 -0700 (PDT) Subject: Re: [PATCH v2 08/50] target/i386: Assert IOPL is 0 for user-only To: Richard Henderson , qemu-devel@nongnu.org References: <20210514151342.384376-1-richard.henderson@linaro.org> <20210514151342.384376-9-richard.henderson@linaro.org> From: Paolo Bonzini Message-ID: <5d26054f-866d-af88-5b01-079c8d1350a2@redhat.com> Date: Tue, 18 May 2021 11:18:59 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210514151342.384376-9-richard.henderson@linaro.org> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=pbonzini@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.374, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: cfontana@suse.de, f4bug@amsat.org, ehabkost@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 14/05/21 17:13, Richard Henderson wrote: > On real hardware, the linux kernel has the iopl(2) syscall which > can set IOPL to 3, to allow e.g. the xserver to briefly disable > interrupts while programming the graphics card. > > However, QEMU cannot and does not implement this syscall, so the > IOPL is never changed from 0. Which means that all of the checks > vs CPL <= IOPL are false for user-only. > > Signed-off-by: Richard Henderson Reviewed-by: Paolo Bonzini