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Authentication-Results: esa1.hc3370-68.iphmx.com; dkim=none (message not signed) header.i=none IronPort-SDR: sTMiV0CrnjHyYLETWirfhUTpObTkYBt5Z8zksrqayeCnzf7NCn2EUHPyFV3jKVsTEWKMzKgH9T bRwbdfaATlHWh8kRhdaOdin0v+2yP22RqMdyQ/hYkjmZ7tOo83lRbor30d7qN6/7denJNSk5hb VwfuhvIvXyZkQZhwcHWBpObuL11b9yeJcsnAaBUHM3vgSbF0qrOOEscyp+Ew9RFR4v7GA7Xmsa GFQxALddI3ELBToF96rC1HD9vnB5skpAxX7Y+KiatIKBdog71K3rcOyWgloqpmtAs+nuSZxMeK nKg= X-SBRS: 2.5 X-MesageID: 29303081 X-Ironport-Server: esa1.hc3370-68.iphmx.com X-Remote-IP: 162.221.158.21 X-Policy: $RELAYED X-IronPort-AV: E=Sophos;i="5.77,374,1596513600"; d="scan'208";a="29303081" Subject: Re: [PATCH] xen/arm: Warn user on cpu errata 832075 To: Bertrand Marquis , CC: Stefano Stabellini , Julien Grall , Volodymyr Babchuk References: From: Andrew Cooper Message-ID: <26742825-25fc-0f82-2b20-d536e8380b2a@citrix.com> Date: Wed, 14 Oct 2020 12:35:15 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Content-Language: en-GB X-ClientProxiedBy: AMSPEX02CAS02.citrite.net (10.69.22.113) To FTLPEX02CL05.citrite.net (10.13.108.178) On 14/10/2020 11:41, Bertrand Marquis wrote: > When a Cortex A57 processor is affected by CPU errata 832075, a guest > not implementing the workaround for it could deadlock the system. > Add a warning during boot informing the user that only trusted guests > should be executed on the system. > An equivalent warning is already given to the user by KVM on cores > affected by this errata. > > Signed-off-by: Bertrand Marquis > --- > xen/arch/arm/cpuerrata.c | 21 +++++++++++++++++++++ > 1 file changed, 21 insertions(+) > > diff --git a/xen/arch/arm/cpuerrata.c b/xen/arch/arm/cpuerrata.c > index 6c09017515..8f9ab6dde1 100644 > --- a/xen/arch/arm/cpuerrata.c > +++ b/xen/arch/arm/cpuerrata.c > @@ -240,6 +240,26 @@ static int enable_ic_inv_hardening(void *data) > > #endif > > +#ifdef CONFIG_ARM64_ERRATUM_832075 > + > +static int warn_device_load_acquire_errata(void *data) > +{ > + static bool warned = false; > + > + if ( !warned ) > + { > + warning_add("This CPU is affected by the errata 832075.\n" > + "Guests without required CPU erratum workarounds\n" > + "can deadlock the system!\n" > + "Only trusted guests should be used on this system.\n"); > + warned = true; This is an antipattern, which probably wants fixing elsewhere as well. warning_add() is __init.  It's not legitimate to call from a non-init function, and a less useless build system would have modpost to object. The ARM_SMCCC_ARCH_WORKAROUND_1 instance asserts based on system state, but this provides no safety at all. What warning_add() actually does is queue messages for some point near the end of boot.  It's not clear that this is even a clever thing to do. I'm very tempted to suggest a blanket change to printk_once(). ~Andrew > + } > + > + return 0; > +} > + > +#endif > + > #ifdef CONFIG_ARM_SSBD > > enum ssbd_state ssbd_state = ARM_SSBD_RUNTIME; > @@ -419,6 +439,7 @@ static const struct arm_cpu_capabilities arm_errata[] = { > .capability = ARM64_WORKAROUND_DEVICE_LOAD_ACQUIRE, > MIDR_RANGE(MIDR_CORTEX_A57, 0x00, > (1 << MIDR_VARIANT_SHIFT) | 2), > + .enable = warn_device_load_acquire_errata, > }, > #endif > #ifdef CONFIG_ARM64_ERRATUM_834220