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[86.183.162.242]) by smtp.gmail.com with ESMTPSA id z184sm20781200wmg.7.2021.01.18.02.00.51 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Mon, 18 Jan 2021 02:00:51 -0800 (PST) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 6bd6e0f0-19a8-41ce-8220-471187c4c8d1 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:reply-to:to:cc:references:in-reply-to:subject:date:message-id :mime-version:content-transfer-encoding:thread-index :content-language; bh=KsPfvnXYgbL4awXzyfP6HuKFWuYK7XNLYWDLhybndi0=; b=D7hVwezld4bB/X4x/RsD/C67PeydIqK17WbLGLJeIqTPMBr2zzIPxrTH4mApeKN0l2 Il2lg0aYx9BCla/ehpSJfnqyOU+olRBEYFJZZJv0eOm2H0g+6dhPK55vFCyJoMjib89k WkXBmmYtRISbRODYeNe8PO5FE5eOlF1rkptQ4+3zRZ8w6C245X7GMWqfCL1lQ5stuUqA qrNkIHUaH3/QMayIoEDNhO+q/726kTZC/fymbxJLnpOIigppUAvyzz8SltV1JYEaMV97 zHawCy6j5TUUSoU4IUdE9lHwzDporv2SVqW8P+edsTezG6xJEFUOupaAxsoU2ebWRmlW Kytg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:reply-to:to:cc:references:in-reply-to :subject:date:message-id:mime-version:content-transfer-encoding :thread-index:content-language; bh=KsPfvnXYgbL4awXzyfP6HuKFWuYK7XNLYWDLhybndi0=; b=LHfjKNwWNh9WBclQGzCoaP5GcVw6SYeskEuoPPcYnl9XAMqELNfbEd8UiQI7IDeCN4 u7s/Yb37QofU4G5JHhX6QY99Oauy04OtH/YyMvnhvt3Rrq93Lx1Tab6bl5mcdBtngviD skJI+YOykoc/NU+uphSol9Wn06QsvxzUzetFvnlxK9MTuzep10mtHc5ry5fRWdKUZ0mw qm2KpZ/UY7AvCfrC27Y20lZ9/37x7SED2kGII7V93CIRaIW5pAoGIWcbO3dpVK1TFgmK XE/T1MaUXqL/twh0SCFEadZtoWOAjypQ5x9E3w7y6sR/GPAhRREDg3Rzc2Xi0B5dzJOz QoAg== X-Gm-Message-State: AOAM533Lvi6DLTGdkyA+q0xowuRBKkPuw5WQGrGoaVckPRrp8d6uH8tz OcLU+K35TJmNi1IzgSV//dg= X-Google-Smtp-Source: ABdhPJylKkXl+EY1vawUDMUGlZqSJ+rJ5L5/1gs97UqJfMvZrbhcsr1ny7xkyGQBA9CdPOVY3cIXVg== X-Received: by 2002:adf:e552:: with SMTP id z18mr26078842wrm.29.1610964052205; Mon, 18 Jan 2021 02:00:52 -0800 (PST) From: Paul Durrant X-Google-Original-From: "Paul Durrant" Reply-To: To: "'Oleksandr Tyshchenko'" , Cc: "'Oleksandr Tyshchenko'" , "'Julien Grall'" , "'Stefano Stabellini'" , "'Julien Grall'" References: <1610488352-18494-1-git-send-email-olekstysh@gmail.com> <1610488352-18494-14-git-send-email-olekstysh@gmail.com> In-Reply-To: <1610488352-18494-14-git-send-email-olekstysh@gmail.com> Subject: RE: [PATCH V4 13/24] xen/ioreq: Use guest_cmpxchg64() instead of cmpxchg() Date: Mon, 18 Jan 2021 10:00:50 -0000 Message-ID: <00cc01d6ed80$cdb8b780$692a2680$@xen.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Outlook 16.0 Thread-Index: AQJtR7ihpnpDvKGK8VeC26+r2ffFKQENHQG2qPgIfJA= Content-Language: en-gb > -----Original Message----- > From: Xen-devel On Behalf Of Oleksandr Tyshchenko > Sent: 12 January 2021 21:52 > To: xen-devel@lists.xenproject.org > Cc: Oleksandr Tyshchenko ; Paul Durrant ; Julien Grall > ; Stefano Stabellini ; Julien Grall > Subject: [PATCH V4 13/24] xen/ioreq: Use guest_cmpxchg64() instead of cmpxchg() > > From: Oleksandr Tyshchenko > > The cmpxchg() in ioreq_send_buffered() operates on memory shared > with the emulator domain (and the target domain if the legacy > interface is used). > > In order to be on the safe side we need to switch > to guest_cmpxchg64() to prevent a domain to DoS Xen on Arm. > > As there is no plan to support the legacy interface on Arm, > we will have a page to be mapped in a single domain at the time, > so we can use s->emulator in guest_cmpxchg64() safely. > > Thankfully the only user of the legacy interface is x86 so far > and there is not concern regarding the atomics operations. > > Please note, that the legacy interface *must* not be used on Arm > without revisiting the code. > > Signed-off-by: Oleksandr Tyshchenko > Acked-by: Stefano Stabellini > CC: Julien Grall > [On Arm only] > Tested-by: Wei Chen Reviewed-by: Paul Durrant