Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Tue, 27 Jun 2023 17:48:02 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Petr =?utf-8?B?VGVzYcWZw61r?= <petr@tesarici.cz>
Cc:     Robin Murphy <robin.murphy@arm.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Petr Tesarik <petrtesarik@huaweicloud.com>,
        Stefano Stabellini <sstabellini@kernel.org>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Juergen Gross <jgross@suse.com>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>,
        Christoph Hellwig <hch@lst.de>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Hans de Goede <hdegoede@redhat.com>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Kees Cook <keescook@chromium.org>,
        Saravana Kannan <saravanak@google.com>,
        "moderated list:XEN HYPERVISOR ARM" <xen-devel@lists.xenproject.org>,
        "moderated list:ARM PORT" <linux-arm-kernel@lists.infradead.org>,
        open list <linux-kernel@vger.kernel.org>,
        "open list:MIPS" <linux-mips@vger.kernel.org>,
        "open list:XEN SWIOTLB SUBSYSTEM" <iommu@lists.linux.dev>,
        Roberto Sassu <roberto.sassu@huaweicloud.com>,
        Kefeng Wang <wangkefeng.wang@huawei.com>
Subject: Re: [PATCH v3 1/7] swiotlb: make io_tlb_default_mem local to
 swiotlb.c
Message-ID: <20230627154802.GA29567@lst.de>
References: <cover.1687859323.git.petr.tesarik.ext@huawei.com> <a1ef6eeab8b64fac817b9734da4a056f05a68d01.1687859323.git.petr.tesarik.ext@huawei.com> <2023062745-routing-palace-d0b4@gregkh> <73f11258-1562-17c1-969e-b134dcb5f35c@arm.com> <20230627133006.16ee11af@meshulam.tesarici.cz>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <20230627133006.16ee11af@meshulam.tesarici.cz>
User-Agent: Mutt/1.5.17 (2007-11-01)
Precedence: bulk

On Tue, Jun 27, 2023 at 01:30:06PM +0200, Petr Tesařík wrote:
> Xen is the only user of an "is SWIOTLB present" interface. IIUC Xen
> needs bounce buffers for the PCI frontend driver, but if there is no
> other reason to have a SWIOTLB, the system does not set up one at boot.

Please take a look at my "unexport swiotlb_active v2" series that
unfortunately missed the 6.5 merge window waiting for reviews.