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[88.187.86.199]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43996aa820dsm16090465e9.5.2025.02.18.07.25.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 Feb 2025 07:25:56 -0800 (PST) Message-ID: <3fb630f4-ebd2-4f14-a1fe-4e84786a1400@linaro.org> Date: Tue, 18 Feb 2025 16:25:55 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PULL 3/9] meson: Disallow 64-bit on 32-bit Xen emulation To: Andrew Cooper , qemu-devel@nongnu.org, David Woodhouse , "open list:X86 Xen CPUs" , Paul Durrant , Stefano Stabellini , Anthony PERARD , "Edgar E. Iglesias" , Vikram Garhwal Cc: Thomas Huth , Richard Henderson , qemu-arm , =?UTF-8?Q?Alex_Benn=C3=A9e?= , =?UTF-8?Q?Daniel_P=2E_Berrang=C3=A9?= References: <20250208205725.568631-1-richard.henderson@linaro.org> <20250208205725.568631-4-richard.henderson@linaro.org> <9b22d0ff-5902-4ec7-ae54-e974482ebd87@citrix.com> Content-Language: en-US From: =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= In-Reply-To: <9b22d0ff-5902-4ec7-ae54-e974482ebd87@citrix.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::330; envelope-from=philmd@linaro.org; helo=mail-wm1-x330.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=unavailable 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 +Vikram On 18/2/25 15:10, Andrew Cooper wrote: > On 18/02/2025 11:20 am, Philippe Mathieu-Daudé wrote: >> Hi, >> >> Adding Xen community. >> >> On 8/2/25 21:57, Richard Henderson wrote: >>> Require a 64-bit host binary to spawn a 64-bit guest. >>> >>> Reviewed-by: Thomas Huth >>> Reviewed-by: Philippe Mathieu-Daudé >>> Signed-off-by: Richard Henderson >>> --- >>>   meson.build | 9 +++++++-- >>>   1 file changed, 7 insertions(+), 2 deletions(-) >>> >>> diff --git a/meson.build b/meson.build >>> index 1af8aeb194..911955cfa8 100644 >>> --- a/meson.build >>> +++ b/meson.build >>> @@ -304,9 +304,14 @@ else >>>   endif >>>   accelerator_targets = { 'CONFIG_KVM': kvm_targets } >>>   -if cpu in ['x86', 'x86_64'] >>> +if cpu == 'x86' >>> +  xen_targets = ['i386-softmmu'] >>> +elif cpu == 'x86_64' >>>     xen_targets = ['i386-softmmu', 'x86_64-softmmu'] >>> -elif cpu in ['arm', 'aarch64'] >>> +elif cpu == 'arm' >>> +  # i386 emulator provides xenpv machine type for multiple >>> architectures >>> +  xen_targets = ['i386-softmmu'] >> >> Is actually someone *testing* this config? I'm having hard time building >> it, so am very suspicious about how it runs, and start to wonder if I'm >> not just wasting my time (as could be our CI). > > It was intentional.  I believe it was Stefano (CC'd) who introduced it. In the introduction commit, "ARM targets" is used, so apparently both 32/64bit were picked deliberately: --- commit aaea616d54317b8a0154adf52303a51da2d8d56f Author: Vikram Garhwal Date: Wed Jun 14 17:03:38 2023 -0700 meson.build: enable xenpv machine build for ARM Add CONFIG_XEN for aarch64 device to support build for ARM targets. Signed-off-by: Vikram Garhwal Signed-off-by: Stefano Stabellini Reviewed-by: Alex Bennée diff --git a/meson.build b/meson.build index 481865bfa97..cfa98e9e25f 100644 --- a/meson.build +++ b/meson.build @@ -136,7 +136,7 @@ endif if cpu in ['x86', 'x86_64', 'arm', 'aarch64'] # i386 emulator provides xenpv machine type for multiple architectures accelerator_targets += { - 'CONFIG_XEN': ['i386-softmmu', 'x86_64-softmmu'], + 'CONFIG_XEN': ['i386-softmmu', 'x86_64-softmmu', 'aarch64-softmmu'], } endif if cpu in ['x86', 'x86_64'] --- > Xen uses qemu-system-i386 everywhere because qemu-system-x86_64 doesn't > make compatible VMs.  I'm not sure why; I suspect it's bugs in the Xen > machine types, but I don't know QEMU well enough to be sure. > > Another thing that (at least, was) tied to qemu-system-i386 was using > Qemu as a XenBlk <-> QCOW adapter, at which point it wasn't even really > a system emulator, just a paravirtual disk implementation. > > This is, AIUI, what ARM wants with the xenpv machine.  If there's a > better way to do this, please do say. No, I concur. > Looking through Xen's CI, I can't see any of the ARM builds building > QEMU at all.  I think it's quite possible it's not tested any more. We only cross-build, see our cross-arm64-xen-only job: https://gitlab.com/qemu-project/qemu/-/jobs/9165958873 Note, if it is not clear, the problem I have is to test Xen on 32-bit ARM hosts; I don't have any problem with 64-bit ones. Regards, Phil.