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[88.187.86.199]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43bdd9471b7sm74584175e9.34.2025.03.07.23.48.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 07 Mar 2025 23:48:18 -0800 (PST) Message-ID: <85901dab-29a5-4d50-b122-29333f7ebcd9@linaro.org> Date: Sat, 8 Mar 2025 08:48:17 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 10/14] system/iommufd: Introduce iommufd_builtin() helper To: Richard Henderson , qemu-devel@nongnu.org Cc: Alex Williamson References: <20250307180337.14811-1-philmd@linaro.org> <20250307180337.14811-11-philmd@linaro.org> <1e7b5507-e226-44bd-afec-0261ee3549ce@linaro.org> Content-Language: en-US From: =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= In-Reply-To: <1e7b5507-e226-44bd-afec-0261ee3549ce@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::430; envelope-from=philmd@linaro.org; helo=mail-wr1-x430.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, 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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 7/3/25 21:33, Richard Henderson wrote: > On 3/7/25 10:03, Philippe Mathieu-Daudé wrote: >> iommufd_builtin() can be used to check at runtime whether >> the IOMMUFD feature is built in a qemu-system binary. >> >> Signed-off-by: Philippe Mathieu-Daudé >> --- >>   docs/devel/vfio-iommufd.rst | 2 +- >>   include/system/iommufd.h    | 8 ++++++++ >>   2 files changed, 9 insertions(+), 1 deletion(-) >> >> diff --git a/docs/devel/vfio-iommufd.rst b/docs/devel/vfio-iommufd.rst >> index 3d1c11f175e..08882094eee 100644 >> --- a/docs/devel/vfio-iommufd.rst >> +++ b/docs/devel/vfio-iommufd.rst >> @@ -88,7 +88,7 @@ Step 2: configure QEMU >>   ---------------------- >>   Interactions with the ``/dev/iommu`` are abstracted by a new iommufd >> -object (compiled in with the ``CONFIG_IOMMUFD`` option). >> +object (which availability can be checked at runtime using >> ``iommufd_builtin()``). >>   Any QEMU device (e.g. VFIO device) wishing to use ``/dev/iommu`` must >>   be linked with an iommufd object. It gets a new optional property >> diff --git a/include/system/iommufd.h b/include/system/iommufd.h >> index cbab75bfbf6..ce459254025 100644 >> --- a/include/system/iommufd.h >> +++ b/include/system/iommufd.h >> @@ -63,4 +63,12 @@ bool >> iommufd_backend_get_dirty_bitmap(IOMMUFDBackend *be, uint32_t hwpt_id, >>                                         Error **errp); >>   #define TYPE_HOST_IOMMU_DEVICE_IOMMUFD TYPE_HOST_IOMMU_DEVICE "- >> iommufd" >> + >> +static inline bool iommufd_builtin(void) >> +{ >> +    bool ambig = false; >> + >> +    return object_resolve_path_type("", TYPE_IOMMUFD_BACKEND, &ambig) >> || ambig; >> +} >> + >>   #endif > > Interesting solution. Actually this isn't appropriate as this checks for an *instance*, while we only want the *class*. I'll respin a different approach.