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Tue, 13 Oct 2020 18:52:34 +0000 (UTC) IronPort-SDR: RlTZCfY2QgDqoWSqF2waagh6Cml19grvNrOyWdyG6hnoztbm/6qbZVxzXAMQNtppnU8Tyr1Ehv vHw+GyQq7Kvw== X-IronPort-AV: E=McAfee;i="6000,8403,9773"; a="227607166" X-IronPort-AV: E=Sophos;i="5.77,371,1596524400"; d="scan'208";a="227607166" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Oct 2020 11:52:33 -0700 IronPort-SDR: YNOb6LIzA6acbBjbhB0XEpPG7GsBsguHAmJu7laXwpuUdWjDQyddEMfR/ePX0qvLiQ40lmlKC/ 51BxLz1q6ZyA== X-IronPort-AV: E=Sophos;i="5.77,371,1596524400"; d="scan'208";a="346282543" Received: from murawskx-mobl.amr.corp.intel.com (HELO [10.209.9.29]) ([10.209.9.29]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Oct 2020 11:52:32 -0700 Subject: Re: [PATCH RFC V3 7/9] x86/entry: Preserve PKRS MSR across exceptions To: ira.weiny@intel.com, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Andy Lutomirski , Peter Zijlstra Cc: Dave Hansen , x86@kernel.org, Dan Williams , Andrew Morton , Fenghua Yu , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org References: <20201009194258.3207172-1-ira.weiny@intel.com> <20201009194258.3207172-8-ira.weiny@intel.com> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201009194258.3207172-8-ira.weiny@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable 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 10/9/20 12:42 PM, ira.weiny@intel.com wrote: > @@ -341,6 +341,9 @@ noinstr void irqentry_enter(struct pt_regs *regs, i= rqentry_state_t *state) > /* Use the combo lockdep/tracing function */ > trace_hardirqs_off(); > instrumentation_end(); > + > +done: > + irq_save_pkrs(state); > } One nit: This saves *and* sets PKRS. It's not obvious from the call here that PKRS is altered at this site. Seems like there could be a better name. Even if we did: irq_save_set_pkrs(state, INIT_VAL); It would probably compile down to the same thing, but be *really* obvious what's going on. > void irqentry_exit_cond_resched(void) > @@ -362,7 +365,12 @@ noinstr void irqentry_exit(struct pt_regs *regs, i= rqentry_state_t *state) > /* Check whether this returns to user mode */ > if (user_mode(regs)) { > irqentry_exit_to_user_mode(regs); > - } else if (!regs_irqs_disabled(regs)) { > + return; > + } > + > + irq_restore_pkrs(state); > + > + if (!regs_irqs_disabled(regs)) { > /* > * If RCU was not watching on entry this needs to be done > * carefully and needs the same ordering of lockdep/tracing >=20