On Wed, Oct 21, 2020 at 08:29:58PM -0700, Stephen Boyd wrote: > According to the SMCCC spec[1](7.5.2 Discovery) the > ARM_SMCCC_ARCH_WORKAROUND_1 function id only returns 0, 1, and > SMCCC_RET_NOT_SUPPORTED. > > 0 is "workaround required and safe to call this function" > 1 is "workaround not required but safe to call this function" > SMCCC_RET_NOT_SUPPORTED is "might be vulnerable or might not be, who knows, I give up!" > > SMCCC_RET_NOT_SUPPORTED might as well mean "workaround required, except > calling this function may not work because it isn't implemented in some > cases". Wonderful. We map this SMC call to > > 0 is SPECTRE_MITIGATED > 1 is SPECTRE_UNAFFECTED > SMCCC_RET_NOT_SUPPORTED is SPECTRE_VULNERABLE > > For KVM hypercalls (hvc), we've implemented this function id to return > SMCCC_RET_NOT_SUPPORTED, 0, and SMCCC_RET_NOT_REQUIRED. One of those > isn't supposed to be there. Per the code we call > arm64_get_spectre_v2_state() to figure out what to return for this > feature discovery call. > > 0 is SPECTRE_MITIGATED > SMCCC_RET_NOT_REQUIRED is SPECTRE_UNAFFECTED > SMCCC_RET_NOT_SUPPORTED is SPECTRE_VULNERABLE > > Let's clean this up so that KVM tells the guest this mapping: > > 0 is SPECTRE_MITIGATED > 1 is SPECTRE_UNAFFECTED > SMCCC_RET_NOT_SUPPORTED is SPECTRE_VULNERABLE > > (Note: Moving SMCCC_RET_NOT_AFFECTED to a header is left out of this > patch as it would need to move from proton-pack.c which isn't in stable > trees and the name isn't actually part of the SMCCC spec) Given that -rc1 is just round the corner, let's pick this up for -rc2 and stick the #define into asm/spectre.h at the same time. The #define is called 'SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED' to make it clear that it's specific to the "ARCH_WORKAROUND" bits. Will
