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[88.21.68.214]) by smtp.gmail.com with ESMTPSA id a1sm7176764ejk.125.2020.07.27.07.26.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Jul 2020 07:26:02 -0700 (PDT) Subject: Re: [PATCH v3 3/8] ppc/spapr: Use start-powered-off CPUState property To: Thiago Jung Bauermann , qemu-ppc@nongnu.org References: <20200723025657.644724-1-bauerman@linux.ibm.com> <20200723025657.644724-4-bauerman@linux.ibm.com> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Autocrypt: addr=philmd@redhat.com; keydata= mQINBDXML8YBEADXCtUkDBKQvNsQA7sDpw6YLE/1tKHwm24A1au9Hfy/OFmkpzo+MD+dYc+7 bvnqWAeGweq2SDq8zbzFZ1gJBd6+e5v1a/UrTxvwBk51yEkadrpRbi+r2bDpTJwXc/uEtYAB GvsTZMtiQVA4kRID1KCdgLa3zztPLCj5H1VZhqZsiGvXa/nMIlhvacRXdbgllPPJ72cLUkXf z1Zu4AkEKpccZaJspmLWGSzGu6UTZ7UfVeR2Hcc2KI9oZB1qthmZ1+PZyGZ/Dy+z+zklC0xl XIpQPmnfy9+/1hj1LzJ+pe3HzEodtlVA+rdttSvA6nmHKIt8Ul6b/h1DFTmUT1lN1WbAGxmg CH1O26cz5nTrzdjoqC/b8PpZiT0kO5MKKgiu5S4PRIxW2+RA4H9nq7nztNZ1Y39bDpzwE5Sp bDHzd5owmLxMLZAINtCtQuRbSOcMjZlg4zohA9TQP9krGIk+qTR+H4CV22sWldSkVtsoTaA2 qNeSJhfHQY0TyQvFbqRsSNIe2gTDzzEQ8itsmdHHE/yzhcCVvlUzXhAT6pIN0OT+cdsTTfif MIcDboys92auTuJ7U+4jWF1+WUaJ8gDL69ThAsu7mGDBbm80P3vvUZ4fQM14NkxOnuGRrJxO qjWNJ2ZUxgyHAh5TCxMLKWZoL5hpnvx3dF3Ti9HW2dsUUWICSQARAQABtDJQaGlsaXBwZSBN YXRoaWV1LURhdWTDqSAoUGhpbCkgPHBoaWxtZEByZWRoYXQuY29tPokCVQQTAQgAPwIbDwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4AWIQSJweePYB7obIZ0lcuio/1u3q3A3gUCXsfWwAUJ KtymWgAKCRCio/1u3q3A3ircD/9Vjh3aFNJ3uF3hddeoFg1H038wZr/xi8/rX27M1Vj2j9VH 0B8Olp4KUQw/hyO6kUxqkoojmzRpmzvlpZ0cUiZJo2bQIWnvScyHxFCv33kHe+YEIqoJlaQc JfKYlbCoubz+02E2A6bFD9+BvCY0LBbEj5POwyKGiDMjHKCGuzSuDRbCn0Mz4kCa7nFMF5Jv piC+JemRdiBd6102ThqgIsyGEBXuf1sy0QIVyXgaqr9O2b/0VoXpQId7yY7OJuYYxs7kQoXI 6WzSMpmuXGkmfxOgbc/L6YbzB0JOriX0iRClxu4dEUg8Bs2pNnr6huY2Ft+qb41RzCJvvMyu gS32LfN0bTZ6Qm2A8ayMtUQgnwZDSO23OKgQWZVglGliY3ezHZ6lVwC24Vjkmq/2yBSLakZE 6DZUjZzCW1nvtRK05ebyK6tofRsx8xB8pL/kcBb9nCuh70aLR+5cmE41X4O+MVJbwfP5s/RW 9BFSL3qgXuXso/3XuWTQjJJGgKhB6xXjMmb1J4q/h5IuVV4juv1Fem9sfmyrh+Wi5V1IzKI7 RPJ3KVb937eBgSENk53P0gUorwzUcO+ASEo3Z1cBKkJSPigDbeEjVfXQMzNt0oDRzpQqH2vp apo2jHnidWt8BsckuWZpxcZ9+/9obQ55DyVQHGiTN39hkETy3Emdnz1JVHTU0Q== Message-ID: <1d97ef8a-13fc-201d-1fbd-263397a6021c@redhat.com> Date: Mon, 27 Jul 2020 16:25:59 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200723025657.644724-4-bauerman@linux.ibm.com> Content-Language: en-US X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=205.139.110.120; envelope-from=philmd@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/27 01:44:14 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -40 X-Spam_score: -4.1 X-Spam_bar: ---- X-Spam_report: (-4.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-1, 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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Aleksandar Rikalo , Eduardo Habkost , Aleksandar Markovic , Cornelia Huck , Mark Cave-Ayland , qemu-devel@nongnu.org, Greg Kurz , qemu-s390x@nongnu.org, qemu-arm@nongnu.org, Artyom Tarasenko , Thomas Huth , Paolo Bonzini , David Hildenbrand , Richard Henderson , =?UTF-8?Q?Alex_Benn=c3=a9e?= , Aurelien Jarno , David Gibson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 7/23/20 4:56 AM, Thiago Jung Bauermann wrote: > PowerPC sPAPR CPUs start in the halted state, and spapr_reset_vcpu() > attempts to implement this by setting CPUState::halted to 1. But that's too > late for the case of hotplugged CPUs in a machine configure with 2 or more > threads per core. > > By then, other parts of QEMU have already caused the vCPU to run in an > unitialized state a couple of times. For example, ppc_cpu_reset() calls > ppc_tlb_invalidate_all(), which ends up calling async_run_on_cpu(). This > kicks the new vCPU while it has CPUState::halted = 0, causing QEMU to issue > a KVM_RUN ioctl on the new vCPU before the guest is able to make the > start-cpu RTAS call to initialize its register state. > > This problem doesn't seem to cause visible issues for regular guests, but > on a secure guest running under the Ultravisor it does. The Ultravisor > relies on being able to snoop on the start-cpu RTAS call to map vCPUs to > guests, and this issue causes it to see a stray vCPU that doesn't belong to > any guest. > > Fix by setting the start-powered-off CPUState property in > spapr_create_vcpu(), which makes cpu_common_reset() initialize > CPUState::halted to 1 at an earlier moment. > > Suggested-by: Eduardo Habkost > Signed-off-by: Thiago Jung Bauermann > --- > hw/ppc/spapr_cpu_core.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > NB: Tested on ppc64le pseries KVM guest with two threads per core. > Hot-plugging additional cores doesn't cause the bug described above > anymore. > > diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c > index c4f47dcc04..2125fdac34 100644 > --- a/hw/ppc/spapr_cpu_core.c > +++ b/hw/ppc/spapr_cpu_core.c > @@ -36,11 +36,6 @@ static void spapr_reset_vcpu(PowerPCCPU *cpu) > > cpu_reset(cs); > > - /* All CPUs start halted. CPU0 is unhalted from the machine level > - * reset code and the rest are explicitly started up by the guest > - * using an RTAS call */ > - cs->halted = 1; > - > env->spr[SPR_HIOR] = 0; > > lpcr = env->spr[SPR_LPCR]; > @@ -274,6 +269,11 @@ static PowerPCCPU *spapr_create_vcpu(SpaprCpuCore *sc, int i, Error **errp) > > cs = CPU(obj); > cpu = POWERPC_CPU(obj); > + /* > + * All CPUs start halted. CPU0 is unhalted from the machine level reset code > + * and the rest are explicitly started up by the guest using an RTAS call. > + */ > + cs->start_powered_off = true; > cs->cpu_index = cc->core_id + i; > spapr_set_vcpu_id(cpu, cs->cpu_index, &local_err); > if (local_err) { > Reviewed-by: Philippe Mathieu-Daudé