From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E77CAC25B74 for ; Tue, 21 May 2024 14:31:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=umoS6UboO3ihtosdnXvTlPsAK6QgteDhQaisVgcUazk=; b=mbgRS0mJgKyryH E5qIk9u5xQJLNNo8Ru+YCKx6WBVIN6bYV4Lys4sSkP8elKSADfoHqzxnXsM5KvyXLayYdwWrx9FHI vMNaw8eNhm67YRQkyQoXv4q9ULWlZtm+LE+qbhLnKeMC1Qh88bi8i0J7C4ITdjbTEOO/8IZwQXuEo w1T2zwu7+07wQ3XY7QVsb3Tj5zYO9lqx/mBcX5Jle3T1vEl71D6M0UiYvlvt4EwWZzoOdHvovsgZW fnPSV0JxHcI58IseHa542y2hVgsdE5bTVZkNPogtXENxe5BqNK1ziup5NIf8EOEXeDsQxfPcDyP79 hq18xcnkRfxfNSuejVzA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1s9QWD-00000000Bpq-3iRT; Tue, 21 May 2024 14:31:09 +0000 Received: from desiato.infradead.org ([2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1s9PVd-0000000Hb4s-0fEZ for linux-arm-kernel@bombadil.infradead.org; Tue, 21 May 2024 13:26:29 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=rLOEUDuG1dFdDOqOVVZlK717rmhprl7oOHH3MQPd6hQ=; b=UHmfh/Jz1f6PBf+0Cw0E0gj+op TCqAwOwgBZ180GpycDY0HIW5rxN2/BH+fgssPqjXnVTiaP3wxOguAj7uVcomKDLk6++m9UR8Ky0To NY96YFL62FkqBsoWhbe6Nvai9gLBUei449bmfrvWMON9tdeFthcvh9MJ0LM+WucQx8D3jSODCVHKM UGS5w+weBeMW/7HfswHx7ioUge2KpEuM51Bq5S9RgMc51Qb7tNALx9JqzR94n+WkGo5RUOpS6V/dM Kq+fIqCH+fkrk4BeFK5SIsNkAC7mCj68dObjHl97WQJfLfvfxgy6UAsHSJN2mjNtv01hFiZgsg3v8 gt5TP8HQ==; Received: from foss.arm.com ([217.140.110.172]) by desiato.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1s9PVZ-00000006ie2-1qJX for linux-arm-kernel@lists.infradead.org; Tue, 21 May 2024 13:26:27 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 31D38DA7; Tue, 21 May 2024 06:26:48 -0700 (PDT) Received: from J2N7QTR9R3 (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B52E73F641; Tue, 21 May 2024 06:26:21 -0700 (PDT) Date: Tue, 21 May 2024 14:26:19 +0100 From: Mark Rutland To: Anshuman Khandual Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, will@kernel.org, catalin.marinas@arm.com, Mark Brown , James Clark , Rob Herring , Marc Zyngier , Suzuki Poulose , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , linux-perf-users@vger.kernel.org, Oliver Upton , James Morse , kvmarm@lists.linux.dev Subject: Re: [PATCH V17 2/9] KVM: arm64: Explicitly handle BRBE traps as UNDEFINED Message-ID: References: <20240405024639.1179064-1-anshuman.khandual@arm.com> <20240405024639.1179064-3-anshuman.khandual@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20240405024639.1179064-3-anshuman.khandual@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240521_142625_926742_8D75E097 X-CRM114-Status: GOOD ( 36.13 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Anshuman, On Fri, Apr 05, 2024 at 08:16:32AM +0530, Anshuman Khandual wrote: > The Branch Record Buffer Extension (BRBE) adds a number of system registers > and instructions, which we don't currently intend to expose to guests. Our > existing logic handles this safely, but this could be improved with some > explicit handling of BRBE. > > The presence of BRBE is currently hidden from guests as the cpufeature > code's ftr_id_aa64dfr0[] table doesn't have an entry for the BRBE field, > and so this will be zero in the sanitised value of ID_AA64DFR0 exposed to > guests via read_sanitised_id_aa64dfr0_el1(). As the ftr_id_aa64dfr0[] table > may gain an entry for the BRBE field in future, for robustness we should > explicitly mask out the BRBE field in read_sanitised_id_aa64dfr0_el1(). > > The BRBE system registers and instructions are currently trapped by the > existing configuration of the fine-grained traps. As neither the registers > are not described in the sys_reg_descs[] nor the instructions are described > in the sys_insn_descs[] table, emulate_sys_reg() will warn that these are > unknown before injecting an UNDEFINED exception into the guest. That last sentence doesn't make sense, and I think it has been mangled. My suggested text in v16 was: | As the registers and instructions are not described in the | sys_reg_descs[] table, emulate_sys_reg() will warn that these are | unknown before injecting an UNDEFINED exception into the guest. ... and I'd be happy with changing that to: | As neither the registers nor the instructions are described in the | sys_reg_descs[] table, emulate_sys_reg() will warn that these are | unknown before injecting an UNDEFINED exception into the guest. > Well-behaved guests shouldn't try to use the registers or instructions, but > badly-behaved guests could use these, resulting in unnecessary warnings. I see that I had mangled this sentence originally -- thanks for correcting that; this looks fine to me. > To avoid those warnings, we should explicitly handle the BRBE > registers, and instructions as UNDEFINED. I think the added comma is unnecessary and makes this hard to read. My suggested text in v16 was: | To avoid those warnings, we should explicitly handle the BRBE | registers and instructions as UNDEFINED. > Address the above by having read_sanitised_id_aa64dfr0_el1() mask out the > ID_AA64DFR0.BRBE field, and by adding sys_reg_descs entries for all of the > BRBE system registers, also by adding sys_insn_descs entries for all of the > BRBE instructions, treating these all as UNDEFINED. Similarly, I think this was clearer as I originally suggested: | Address the above by having read_sanitised_id_aa64dfr0_el1() mask out | the ID_AA64DFR0.BRBE field, and by adding sys_reg_desc entries for all | of the BRBE system registers and instructions, treating these all as | UNDEFINED. ... or we can simplify that to: | Address the above by having read_sanitised_id_aa64dfr0_el1() mask out | the ID_AA64DFR0.BRBE field, and explicitly handling all of the BRBE | system registers and instructions as UNDEFINED. > Cc: Marc Zyngier > Cc: Oliver Upton > Cc: James Morse > Cc: Suzuki K Poulose > Cc: Catalin Marinas > Cc: Will Deacon > Cc: kvmarm@lists.linux.dev > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Anshuman Khandual > ---- > Changes in V17: > > - Updated the commit message including about sys_insn_descs[] > - Changed KVM to use existing SYS_BRBSRC/TGT/INF_EL1(n) format > - Moved the BRBE instructions into sys_insn_descs[] array Aside from my nits on the commit message above, these changes all look good to me. So with the commit message cleaned up as above: Reviewed-by: Mark Rutland Mark. > > arch/arm64/kvm/sys_regs.c | 56 +++++++++++++++++++++++++++++++++++++++ > 1 file changed, 56 insertions(+) > > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > index c9f4f387155f..3981aa32c5a3 100644 > --- a/arch/arm64/kvm/sys_regs.c > +++ b/arch/arm64/kvm/sys_regs.c > @@ -1304,6 +1304,11 @@ static int set_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r, > return 0; > } > > +#define BRB_INF_SRC_TGT_EL1(n) \ > + { SYS_DESC(SYS_BRBINF_EL1(n)), undef_access }, \ > + { SYS_DESC(SYS_BRBSRC_EL1(n)), undef_access }, \ > + { SYS_DESC(SYS_BRBTGT_EL1(n)), undef_access } \ > + > /* Silly macro to expand the DBG{BCR,BVR,WVR,WCR}n_EL1 registers in one go */ > #define DBG_BCR_BVR_WCR_WVR_EL1(n) \ > { SYS_DESC(SYS_DBGBVRn_EL1(n)), \ > @@ -1708,6 +1713,9 @@ static u64 read_sanitised_id_aa64dfr0_el1(struct kvm_vcpu *vcpu, > /* Hide SPE from guests */ > val &= ~ID_AA64DFR0_EL1_PMSVer_MASK; > > + /* Hide BRBE from guests */ > + val &= ~ID_AA64DFR0_EL1_BRBE_MASK; > + > return val; > } > > @@ -2226,6 +2234,52 @@ static const struct sys_reg_desc sys_reg_descs[] = { > { SYS_DESC(SYS_DBGCLAIMCLR_EL1), trap_raz_wi }, > { SYS_DESC(SYS_DBGAUTHSTATUS_EL1), trap_dbgauthstatus_el1 }, > > + /* > + * BRBE branch record sysreg address space is interleaved between > + * corresponding BRBINF_EL1, BRBSRC_EL1, and BRBTGT_EL1. > + */ > + BRB_INF_SRC_TGT_EL1(0), > + BRB_INF_SRC_TGT_EL1(16), > + BRB_INF_SRC_TGT_EL1(1), > + BRB_INF_SRC_TGT_EL1(17), > + BRB_INF_SRC_TGT_EL1(2), > + BRB_INF_SRC_TGT_EL1(18), > + BRB_INF_SRC_TGT_EL1(3), > + BRB_INF_SRC_TGT_EL1(19), > + BRB_INF_SRC_TGT_EL1(4), > + BRB_INF_SRC_TGT_EL1(20), > + BRB_INF_SRC_TGT_EL1(5), > + BRB_INF_SRC_TGT_EL1(21), > + BRB_INF_SRC_TGT_EL1(6), > + BRB_INF_SRC_TGT_EL1(22), > + BRB_INF_SRC_TGT_EL1(7), > + BRB_INF_SRC_TGT_EL1(23), > + BRB_INF_SRC_TGT_EL1(8), > + BRB_INF_SRC_TGT_EL1(24), > + BRB_INF_SRC_TGT_EL1(9), > + BRB_INF_SRC_TGT_EL1(25), > + BRB_INF_SRC_TGT_EL1(10), > + BRB_INF_SRC_TGT_EL1(26), > + BRB_INF_SRC_TGT_EL1(11), > + BRB_INF_SRC_TGT_EL1(27), > + BRB_INF_SRC_TGT_EL1(12), > + BRB_INF_SRC_TGT_EL1(28), > + BRB_INF_SRC_TGT_EL1(13), > + BRB_INF_SRC_TGT_EL1(29), > + BRB_INF_SRC_TGT_EL1(14), > + BRB_INF_SRC_TGT_EL1(30), > + BRB_INF_SRC_TGT_EL1(15), > + BRB_INF_SRC_TGT_EL1(31), > + > + /* Remaining BRBE sysreg addresses space */ > + { SYS_DESC(SYS_BRBCR_EL1), undef_access }, > + { SYS_DESC(SYS_BRBFCR_EL1), undef_access }, > + { SYS_DESC(SYS_BRBTS_EL1), undef_access }, > + { SYS_DESC(SYS_BRBINFINJ_EL1), undef_access }, > + { SYS_DESC(SYS_BRBSRCINJ_EL1), undef_access }, > + { SYS_DESC(SYS_BRBTGTINJ_EL1), undef_access }, > + { SYS_DESC(SYS_BRBIDR0_EL1), undef_access }, > + > { SYS_DESC(SYS_MDCCSR_EL0), trap_raz_wi }, > { SYS_DESC(SYS_DBGDTR_EL0), trap_raz_wi }, > // DBGDTR[TR]X_EL0 share the same encoding > @@ -2738,6 +2792,8 @@ static struct sys_reg_desc sys_insn_descs[] = { > { SYS_DESC(SYS_DC_CISW), access_dcsw }, > { SYS_DESC(SYS_DC_CIGSW), access_dcgsw }, > { SYS_DESC(SYS_DC_CIGDSW), access_dcgsw }, > + { SYS_DESC(OP_BRB_IALL), undef_access }, > + { SYS_DESC(OP_BRB_INJ), undef_access }, > }; > > static const struct sys_reg_desc *first_idreg; > -- > 2.25.1 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel