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Tue, 22 Sep 2020 13:05:44 -0700 (PDT) Received: from [192.168.1.6] ([212.22.223.21]) by smtp.gmail.com with ESMTPSA id b197sm3830782lfd.251.2020.09.22.13.05.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 22 Sep 2020 13:05:43 -0700 (PDT) Subject: Re: [PATCH V1 14/16] xen/ioreq: Use guest_cmpxchg64() instead of cmpxchg() To: Julien Grall , paul@xen.org, 'Jan Beulich' Cc: xen-devel@lists.xenproject.org, 'Oleksandr Tyshchenko' , 'Stefano Stabellini' , 'Julien Grall' References: <1599769330-17656-1-git-send-email-olekstysh@gmail.com> <1599769330-17656-15-git-send-email-olekstysh@gmail.com> <44b19ee1-dc34-3a46-0b4b-7196faadcb5c@suse.com> <002b01d68c09$12df32a0$389d97e0$@xen.org> From: Oleksandr Message-ID: <3e58dc8a-4ecb-1ed5-3179-82f96cc40ca7@gmail.com> Date: Tue, 22 Sep 2020 23:05:38 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 16.09.20 12:12, Julien Grall wrote: Hi all. > > > On 16/09/2020 10:09, Paul Durrant wrote: >>> -----Original Message----- >>> From: Julien Grall >>> Sent: 16 September 2020 10:07 >>> To: Jan Beulich ; Oleksandr Tyshchenko >>> >>> Cc: xen-devel@lists.xenproject.org; Oleksandr Tyshchenko >>> ; Paul Durrant >>> ; Stefano Stabellini ; Julien >>> Grall >>> Subject: Re: [PATCH V1 14/16] xen/ioreq: Use guest_cmpxchg64() >>> instead of cmpxchg() >>> >>> >>> >>> On 16/09/2020 10:04, Jan Beulich wrote: >>>> On 10.09.2020 22:22, Oleksandr Tyshchenko wrote: >>>>> @@ -1325,7 +1327,7 @@ static int hvm_send_buffered_ioreq(struct >>>>> hvm_ioreq_server *s, ioreq_t *p) >>>>> >>>>>            new.read_pointer = old.read_pointer - n * >>>>> IOREQ_BUFFER_SLOT_NUM; >>>>>            new.write_pointer = old.write_pointer - n * >>>>> IOREQ_BUFFER_SLOT_NUM; >>>>> -        cmpxchg(&pg->ptrs.full, old.full, new.full); >>>>> +        guest_cmpxchg64(d, &pg->ptrs.full, old.full, new.full); >>>> >>>> But the memory we're updating is shared with s->emulator, not with d, >>>> if I'm not mistaken. >>> >>> It is unfortunately shared with both s->emulator and d when using the >>> legacy interface. >> >> When using magic pages they should be punched out of the P2M by the >> time the code gets here, so the memory should not be guest-visible. > > Can you point me to the code that doing this? > > Cheers, > If we are not going to use legacy interface on Arm we will have a page to be mapped in a single domain at the time. I will update patch to use "s->emulator" if no objections. -- Regards, Oleksandr Tyshchenko