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Wed, 14 May 2025 23:14:33 -0700 (PDT) X-Google-Smtp-Source: AGHT+IG3PEe9C8rgBo0TvQnY3+NCOLyFxB24dQVnG16aVk1y3CI+MSZSiHnCWnpwcLn7wNlLIVXpyg== X-Received: by 2002:a05:600c:8289:b0:43d:ea:51d2 with SMTP id 5b1f17b1804b1-442f96ebbdcmr9334755e9.14.1747289673051; Wed, 14 May 2025 23:14:33 -0700 (PDT) Received: from redhat.com ([2a0d:6fc0:1517:1000:ea83:8e5f:3302:3575]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-442f39e8578sm57255445e9.29.2025.05.14.23.14.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 May 2025 23:14:32 -0700 (PDT) Date: Thu, 15 May 2025 02:14:29 -0400 From: "Michael S. Tsirkin" To: Jason Wang Cc: Cindy Lu , michael.christie@oracle.com, sgarzare@redhat.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org Subject: Re: [PATCH v9 4/4] vhost: Add a KConfig knob to enable IOCTL VHOST_FORK_FROM_OWNER Message-ID: <20250515021319-mutt-send-email-mst@kernel.org> References: <20250421024457.112163-5-lulu@redhat.com> <20250429065044-mutt-send-email-mst@kernel.org> <20250430052424-mutt-send-email-mst@kernel.org> <20250513030744-mutt-send-email-mst@kernel.org> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: elSVgxLL4jX5hUt92b04p5JKiOAiI63wHwjV8JeclGs_1747289673 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit On Wed, May 14, 2025 at 10:52:58AM +0800, Jason Wang wrote: > On Tue, May 13, 2025 at 3:09 PM Michael S. Tsirkin wrote: > > > > On Tue, May 13, 2025 at 12:08:51PM +0800, Jason Wang wrote: > > > On Wed, Apr 30, 2025 at 5:27 PM Michael S. Tsirkin wrote: > > > > > > > > On Wed, Apr 30, 2025 at 11:34:49AM +0800, Jason Wang wrote: > > > > > On Tue, Apr 29, 2025 at 6:56 PM Michael S. Tsirkin wrote: > > > > > > > > > > > > On Tue, Apr 29, 2025 at 11:39:37AM +0800, Jason Wang wrote: > > > > > > > On Mon, Apr 21, 2025 at 11:46 AM Jason Wang wrote: > > > > > > > > > > > > > > > > On Mon, Apr 21, 2025 at 11:45 AM Jason Wang wrote: > > > > > > > > > > > > > > > > > > On Mon, Apr 21, 2025 at 10:45 AM Cindy Lu wrote: > > > > > > > > > > > > > > > > > > > > Introduce a new config knob `CONFIG_VHOST_ENABLE_FORK_OWNER_IOCTL`, > > > > > > > > > > to control the availability of the `VHOST_FORK_FROM_OWNER` ioctl. > > > > > > > > > > When CONFIG_VHOST_ENABLE_FORK_OWNER_IOCTL is set to n, the ioctl > > > > > > > > > > is disabled, and any attempt to use it will result in failure. > > > > > > > > > > > > > > > > > > I think we need to describe why the default value was chosen to be false. > > > > > > > > > > > > > > > > > > What's more, should we document the implications here? > > > > > > > > > > > > > > > > > > inherit_owner was set to false: this means "legacy" userspace may > > > > > > > > > > > > > > > > I meant "true" actually. > > > > > > > > > > > > > > MIchael, I'd expect inherit_owner to be false. Otherwise legacy > > > > > > > applications need to be modified in order to get the behaviour > > > > > > > recovered which is an impossible taks. > > > > > > > > > > > > > > Any idea on this? > > > > > > > > > > > > > > Thanks > > > > > > > > So, let's say we had a modparam? Enough for this customer? > > > > WDYT? > > > > > > Just to make sure I understand the proposal. > > > > > > Did you mean a module parameter like "inherit_owner_by_default"? I > > > think it would be fine if we make it false by default. > > > > > > Thanks > > > > I think we should keep it true by default, changing the default > > risks regressing what we already fixes. > > I think it's not a regression since it comes since the day vhost is > introduced. To my understanding the real regression is the user space > noticeable behaviour changes introduced by vhost thread. > > > The specific customer can > > flip the modparam and be happy. > > If you stick to the false as default, I'm fine. > > Thanks That would be yet another behaviour change. I think one was enough, don't you think? > > > > > > > > > > -- > > > > MST > > > > > >