> On 14 Oct 2020, at 12:11, Julien Grall <jul...@xen.org> wrote: > > Hi Bertrand, > > 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. > > I think we should update SUPPORT.MD to say we will not security support those > processors. Stefano, what do you think?
That could make sense to do that yes. If Stefano confirms then i can do this in a v2 > >> An equivalent warning is already given to the user by KVM on cores >> affected by this errata. > > I don't seem to find the warning in Linux. Do you have a link? sure: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=abf532cceaca9c21a148498091f87de1b8ae9b49 > >> Signed-off-by: Bertrand Marquis <bertrand.marq...@arm.com> >> --- >> 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; > > I was going to suggest to use WARN_ON_ONCE() but it looks like it never made > upstream :(. I did do this as it was done in the smc warning function (that’s why i pushed a patch for it). Cheers Bertrand > >> + } >> + >> + 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 > > -- > Julien Grall
