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Peter Anvin" , Paolo Bonzini , Wanpeng Li , Vitaly Kuznetsov , Andy Lutomirski , Peter Zijlstra , Frederic Weisbecker , "Paul E. McKenney" , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Andrew Morton , Uladzislau Rezki , Christoph Hellwig , Lorenzo Stoakes , Jason Baron , Kees Cook , Sami Tolvanen , Ard Biesheuvel , Nicholas Piggin , Juerg Haefliger , Nicolas Saenz Julienne , "Kirill A. Shutemov" , Nadav Amit , Dan Carpenter , Chuang Wang , Yang Jihong , Petr Mladek , "Jason A. Donenfeld" , Song Liu , Julian Pidancet , Tom Lendacky , Dionna Glaze , Thomas =?utf-8?Q?Wei=C3=9Fschuh?= , Juri Lelli , Daniel Bristot de Oliveira , Marcelo Tosatti , Yair Podemsky Subject: Re: [RFC PATCH v2 11/20] objtool: Flesh out warning related to pv_ops[] calls Message-ID: <20230731213631.pywytiwdqgtgx4ps@treble> References: <20230720163056.2564824-1-vschneid@redhat.com> <20230720163056.2564824-12-vschneid@redhat.com> <20230728153334.myvh5sxppvjzd3oz@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Stat-Signature: 1fmja15ozde6jqwtac79kczfrf5pxbrc X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 34EB1C0014 X-HE-Tag: 1690839398-340429 X-HE-Meta: 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 bzzB4JdP I9ewtpjIwD+ich2FAlvR9+NSbNHQ2NJ1JQxYrXd90SQ/mtfNaRH1cvqYUxU3JYj1NnU6SvbcKdAx3DQd1CaGcVuHCUZaODN0nWJfAZqYRCFH7rngeuGkHEDBb4DOtPvNdQhODmTfGzbRfrwliM1Sjua0c8QzW5q0OTnm+QdmzFtq14RIGRF4feTo8bUynnb69ohcGdgQrO/o8CrHsnbKr2q5zFFCv2d2hqiMDNXGltn6lTUSN/S+mYef7T6pZkWQrr+nzInmGuh9w14Rt+NLbwaMJNibxURdweFnO2WvQWjfIswH9UFCDT7asENSMeDW7X05erhlqzBwBa2itcZTG1LikPadiT93oBo55xPCm5Q5545iJDaWXSFbOJqIcjVXtwyfqoDbujdS1SVnejmDhDGJvHg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jul 31, 2023 at 12:16:59PM +0100, Valentin Schneider wrote: > You're quite right - fabricating an artificial warning with a call to __flush_tlb_local(): > > vmlinux.o: warning: objtool: pv_ops[1]: indirect call to native_flush_tlb_local() leaves .noinstr.text section > vmlinux.o: warning: objtool: __flush_tlb_all_noinstr+0x4: call to {dynamic}() leaves .noinstr.text section > > Interestingly the second one doesn't seem to have triggered the "pv_ops" > bit of call_dest_name. Seems like any call to insn_reloc(NULL, x) will > return NULL. Yeah, that's weird. > Trickling down the file yields: > > vmlinux.o: warning: objtool: pv_ops[1]: indirect call to native_flush_tlb_local() leaves .noinstr.text section > vmlinux.o: warning: objtool: __flush_tlb_all_noinstr+0x4: call to pv_ops[0]() leaves .noinstr.text section > > In my case (!PARAVIRT_XXL) pv_ops should look like: > [0]: .cpu.io_delay > [1]: .mmu.flush_tlb_user() > > so pv_ops[1] looks right. Seems like pv_call_dest() gets it right because > it uses arch_dest_reloc_offset(). > > If I use the above to fix up validate_call(), would we still need > pv_call_dest() & co? The functionality in pv_call_dest() is still needed because it goes through all the possible targets for the .mmu.flush_tlb_user() pointer -- xen_flush_tlb() and native_flush_tlb_local() -- and makes sure they're noinstr. Ideally it would only print a single warning for this case, something like: vmlinux.o: warning: objtool: __flush_tlb_all_noinstr+0x4: indirect call to native_flush_tlb_local() leaves .noinstr.text section I left out "pv_ops[1]" because it's already long enough :-) It would need a little bit of code shuffling. But it's really a preexisting problem so don't feel compelled to fix it with this patch set. -- Josh