From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60044) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aHZit-0003ne-Aq for qemu-devel@nongnu.org; Fri, 08 Jan 2016 11:17:08 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aHZiq-0005qU-KJ for qemu-devel@nongnu.org; Fri, 08 Jan 2016 11:17:07 -0500 Received: from foss.arm.com ([217.140.101.70]:45309) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aHZiq-0005q9-CH for qemu-devel@nongnu.org; Fri, 08 Jan 2016 11:17:04 -0500 Date: Fri, 8 Jan 2016 16:18:37 +0000 From: Lorenzo Pieralisi Message-ID: <20160108161837.GA32491@red-moon> References: <1452257667-7967-1-git-send-email-lorenzo.pieralisi@arm.com> <20160108153300.GB11228@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160108153300.GB11228@arm.com> Subject: Re: [Qemu-devel] [PATCH] arm64: kernel: fix PMUv3 registers unconditional access List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Will Deacon Cc: Mark Rutland , Peter Maydell , qemu-devel@nongnu.org, linux-arm-kernel@lists.infradead.org On Fri, Jan 08, 2016 at 03:33:00PM +0000, Will Deacon wrote: [...] > > /* EL2 debug */ > > + mrs x0, id_aa64dfr0_el1 // Check ID_AA64DFR0_EL1 PMUVer > > + ubfx x0, x0, #8, #4 > > + cmp x0, #1 > > + b.ne 4f // Skip if no PMUv3 present > > This will fail if and when PMUVer gets newer revisions of the PMU > architecture (e.g. value 2 to indicate some extended PMU). It looks like > we should be treating it as a signed 4-bit field, so we can use sbfx to > extract a signed value and then we know the PMU is not present if the > value is (signed) less than 1. Sorry about that. Updated patch below, hopefully this time I have got it right (I restested on Juno and QEMU and kept Guenter tested-by tag). Please let me know. Thanks, Lorenzo -- >8 -- Subject: [PATCH] arm64: kernel: fix PMUv3 registers unconditional access The Performance Monitors extension is an optional feature of the AArch64 architecture, therefore, in order to access Performance Monitors registers safely, the kernel should detect the PMUv3 unit presence through the ID_AA64DFR0_EL1 register PMUVer field before accessing them. This patch implements a guard by reading the ID_AA64DFR0_EL1 register PMUVer field to detect the PMUv3 presence and prevent accessing PMUv3 system registers if the Performance Monitors extension is not implemented in the core. Signed-off-by: Lorenzo Pieralisi Reported-by: Guenter Roeck Tested-by: Guenter Roeck Cc: Will Deacon Cc: Peter Maydell Cc: Mark Rutland --- arch/arm64/kernel/head.S | 5 +++++ arch/arm64/mm/proc-macros.S | 12 ++++++++++++ arch/arm64/mm/proc.S | 4 ++-- 3 files changed, 19 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 23cfc08..b685257 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -512,9 +512,14 @@ CPU_LE( movk x0, #0x30d0, lsl #16 ) // Clear EE and E0E on LE systems #endif /* EL2 debug */ + mrs x0, id_aa64dfr0_el1 // Check ID_AA64DFR0_EL1 PMUVer + sbfx x0, x0, #8, #4 + cmp x0, #1 + b.lt 4f // Skip if no PMU present mrs x0, pmcr_el0 // Disable debug access traps ubfx x0, x0, #11, #5 // to EL2 and allow access to msr mdcr_el2, x0 // all PMU counters from EL1 +4: /* Stage-2 translation */ msr vttbr_el2, xzr diff --git a/arch/arm64/mm/proc-macros.S b/arch/arm64/mm/proc-macros.S index 4c4d93c..d69dfff 100644 --- a/arch/arm64/mm/proc-macros.S +++ b/arch/arm64/mm/proc-macros.S @@ -62,3 +62,15 @@ bfi \valreg, \tmpreg, #TCR_T0SZ_OFFSET, #TCR_TxSZ_WIDTH #endif .endm + +/* + * reset_pmuserenr_el0 - reset PMUSERENR_EL0 if PMUv3 present + */ + .macro reset_pmuserenr_el0, tmpreg + mrs \tmpreg, id_aa64dfr0_el1 // Check ID_AA64DFR0_EL1 PMUVer + sbfx \tmpreg, \tmpreg, #8, #4 + cmp \tmpreg, #1 // Skip if no PMU present + b.lt 9000f + msr pmuserenr_el0, xzr // Disable PMU access from EL0 +9000: + .endm diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S index 9c4dce3..b8f04b3 100644 --- a/arch/arm64/mm/proc.S +++ b/arch/arm64/mm/proc.S @@ -117,7 +117,7 @@ ENTRY(cpu_do_resume) */ ubfx x11, x11, #1, #1 msr oslar_el1, x11 - msr pmuserenr_el0, xzr // Disable PMU access from EL0 + reset_pmuserenr_el0 x0 // Disable PMU access from EL0 mov x0, x12 dsb nsh // Make sure local tlb invalidation completed isb @@ -156,7 +156,7 @@ ENTRY(__cpu_setup) msr cpacr_el1, x0 // Enable FP/ASIMD mov x0, #1 << 12 // Reset mdscr_el1 and disable msr mdscr_el1, x0 // access to the DCC from EL0 - msr pmuserenr_el0, xzr // Disable PMU access from EL0 + reset_pmuserenr_el0 x0 // Disable PMU access from EL0 /* * Memory region attributes for LPAE: * -- 2.5.1