On Tue, Nov 03, 2020 at 12:15:26PM -0800, Stephen Boyd wrote:
> commit 1de111b51b829bcf01d2e57971f8fd07a665fa3f upstream.
>
> 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: SMCCC_RET_NOT_AFFECTED is 1 but isn't part of the SMCCC spec
>
> Fixes: c118bbb52743 ("arm64: KVM: Propagate full Spectre v2 workaround state to KVM guests")
> Signed-off-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>
> Acked-by: Marc Zyngier <maz@xxxxxxxxxx>
> Acked-by: Will Deacon <will@xxxxxxxxxx>
> Cc: Andre Przywara <andre.przywara@xxxxxxx>
> Cc: Steven Price <steven.price@xxxxxxx>
> Cc: Marc Zyngier <maz@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Link: https://developer.arm.com/documentation/den0028/latest [1]
> Link: https://lore.kernel.org/r/20201023154751.1973872-1-swboyd@xxxxxxxxxxxx
> Signed-off-by: Will Deacon <will@xxxxxxxxxx>
> Signed-off-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>
> ---
> arch/arm64/kvm/hypercalls.c | 2 +-
> include/linux/arm-smccc.h | 2 ++
> 2 files changed, 3 insertions(+), 1 deletion(-)
Thanks for both of these, now queued up.
greg k-h
