On Wed, 14 Oct 2020, Bertrand Marquis wrote: > > 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
Yes, I confirm > >> 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 > >
