| Message ID | 20201023154751.1973872-1-swboyd@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3] KVM: arm64: ARM_SMCCC_ARCH_WORKAROUND_1 doesn't return SMCCC_RET_NOT_REQUIRED | expand |
On Fri, Oct 23, 2020 at 08:47:50AM -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: SMCCC_RET_NOT_AFFECTED is 1 but isn't part of the SMCCC spec > > Cc: Andre Przywara <andre.przywara@arm.com> > Cc: Steven Price <steven.price@arm.com> > Cc: Marc Zyngier <maz@kernel.org> > Cc: stable@vger.kernel.org > Link: https://developer.arm.com/documentation/den0028/latest [1] > Fixes: c118bbb52743 ("arm64: KVM: Propagate full Spectre v2 workaround state to KVM guests") > Signed-off-by: Stephen Boyd <swboyd@chromium.org> > --- > > I see that before commit c118bbb52743 ("arm64: KVM: Propagate full > Spectre v2 workaround state to KVM guests") we had this mapping: > > 0 is SPECTRE_MITIGATED > SMCCC_RET_NOT_SUPPORTED is SPECTRE_VULNERABLE > > so the return value '1' wasn't there then. Once the commit was merged we > introduced the notion of NOT_REQUIRED here when it shouldn't have been > introduced. > > Changes from v2: > * Moved define to header file and used it > > Changes from v1: > * Way longer commit text, more background (sorry) > * Dropped proton-pack part because it was wrong > * Rebased onto other patch accepted upstream > > arch/arm64/kernel/proton-pack.c | 2 -- > arch/arm64/kvm/hypercalls.c | 2 +- > include/linux/arm-smccc.h | 2 ++ > 3 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/kernel/proton-pack.c b/arch/arm64/kernel/proton-pack.c > index 25f3c80b5ffe..c18eb7d41274 100644 > --- a/arch/arm64/kernel/proton-pack.c > +++ b/arch/arm64/kernel/proton-pack.c > @@ -135,8 +135,6 @@ static enum mitigation_state spectre_v2_get_cpu_hw_mitigation_state(void) > return SPECTRE_VULNERABLE; > } > > -#define SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED (1) > - > static enum mitigation_state spectre_v2_get_cpu_fw_mitigation_state(void) > { > int ret; > diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c > index 9824025ccc5c..25ea4ecb6449 100644 > --- a/arch/arm64/kvm/hypercalls.c > +++ b/arch/arm64/kvm/hypercalls.c > @@ -31,7 +31,7 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu) > val = SMCCC_RET_SUCCESS; > break; > case SPECTRE_UNAFFECTED: > - val = SMCCC_RET_NOT_REQUIRED; > + val = SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED; > break; > } > break; > diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h > index 15c706fb0a37..0e50ba3e88d7 100644 > --- a/include/linux/arm-smccc.h > +++ b/include/linux/arm-smccc.h > @@ -86,6 +86,8 @@ > ARM_SMCCC_SMC_32, \ > 0, 0x7fff) > > +#define SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED 1 I thought we'd stick this in asm/spectre.h, but here is also good: Acked-by: Will Deacon <will@kernel.org> Will
Quoting Will Deacon (2020-10-26 06:25:33) > On Fri, Oct 23, 2020 at 08:47:50AM -0700, Stephen Boyd wrote: > > diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h > > index 15c706fb0a37..0e50ba3e88d7 100644 > > --- a/include/linux/arm-smccc.h > > +++ b/include/linux/arm-smccc.h > > @@ -86,6 +86,8 @@ > > ARM_SMCCC_SMC_32, \ > > 0, 0x7fff) > > > > +#define SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED 1 > > I thought we'd stick this in asm/spectre.h, but here is also good: > > Acked-by: Will Deacon <will@kernel.org> > Ah sorry I glossed over that one. I suppose it can be moved during patch application if desired.
On 2020-10-26 13:25, Will Deacon wrote: > On Fri, Oct 23, 2020 at 08:47:50AM -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: SMCCC_RET_NOT_AFFECTED is 1 but isn't part of the SMCCC spec >> >> Cc: Andre Przywara <andre.przywara@arm.com> >> Cc: Steven Price <steven.price@arm.com> >> Cc: Marc Zyngier <maz@kernel.org> >> Cc: stable@vger.kernel.org >> Link: https://developer.arm.com/documentation/den0028/latest [1] >> Fixes: c118bbb52743 ("arm64: KVM: Propagate full Spectre v2 workaround >> state to KVM guests") >> Signed-off-by: Stephen Boyd <swboyd@chromium.org> >> --- >> >> I see that before commit c118bbb52743 ("arm64: KVM: Propagate full >> Spectre v2 workaround state to KVM guests") we had this mapping: >> >> 0 is SPECTRE_MITIGATED >> SMCCC_RET_NOT_SUPPORTED is SPECTRE_VULNERABLE >> >> so the return value '1' wasn't there then. Once the commit was merged >> we >> introduced the notion of NOT_REQUIRED here when it shouldn't have been >> introduced. >> >> Changes from v2: >> * Moved define to header file and used it >> >> Changes from v1: >> * Way longer commit text, more background (sorry) >> * Dropped proton-pack part because it was wrong >> * Rebased onto other patch accepted upstream >> >> arch/arm64/kernel/proton-pack.c | 2 -- >> arch/arm64/kvm/hypercalls.c | 2 +- >> include/linux/arm-smccc.h | 2 ++ >> 3 files changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/arch/arm64/kernel/proton-pack.c >> b/arch/arm64/kernel/proton-pack.c >> index 25f3c80b5ffe..c18eb7d41274 100644 >> --- a/arch/arm64/kernel/proton-pack.c >> +++ b/arch/arm64/kernel/proton-pack.c >> @@ -135,8 +135,6 @@ static enum mitigation_state >> spectre_v2_get_cpu_hw_mitigation_state(void) >> return SPECTRE_VULNERABLE; >> } >> >> -#define SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED (1) >> - >> static enum mitigation_state >> spectre_v2_get_cpu_fw_mitigation_state(void) >> { >> int ret; >> diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c >> index 9824025ccc5c..25ea4ecb6449 100644 >> --- a/arch/arm64/kvm/hypercalls.c >> +++ b/arch/arm64/kvm/hypercalls.c >> @@ -31,7 +31,7 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu) >> val = SMCCC_RET_SUCCESS; >> break; >> case SPECTRE_UNAFFECTED: >> - val = SMCCC_RET_NOT_REQUIRED; >> + val = SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED; >> break; >> } >> break; >> diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h >> index 15c706fb0a37..0e50ba3e88d7 100644 >> --- a/include/linux/arm-smccc.h >> +++ b/include/linux/arm-smccc.h >> @@ -86,6 +86,8 @@ >> ARM_SMCCC_SMC_32, \ >> 0, 0x7fff) >> >> +#define SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED 1 > > I thought we'd stick this in asm/spectre.h, but here is also good: > > Acked-by: Will Deacon <will@kernel.org> Acked-by: Marc Zyngier <maz@kernel.org> Will, if you're about to send fixes to Linus, can you please pick this one up? M.
On Fri, 23 Oct 2020 08:47:50 -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!" > > [...] Applied to arm64 (for-next/fixes), thanks! [1/1] KVM: arm64: ARM_SMCCC_ARCH_WORKAROUND_1 doesn't return SMCCC_RET_NOT_REQUIRED https://git.kernel.org/arm64/c/1de111b51b82 Cheers,
diff --git a/arch/arm64/kernel/proton-pack.c b/arch/arm64/kernel/proton-pack.c index 25f3c80b5ffe..c18eb7d41274 100644 --- a/arch/arm64/kernel/proton-pack.c +++ b/arch/arm64/kernel/proton-pack.c @@ -135,8 +135,6 @@ static enum mitigation_state spectre_v2_get_cpu_hw_mitigation_state(void) return SPECTRE_VULNERABLE; } -#define SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED (1) - static enum mitigation_state spectre_v2_get_cpu_fw_mitigation_state(void) { int ret; diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c index 9824025ccc5c..25ea4ecb6449 100644 --- a/arch/arm64/kvm/hypercalls.c +++ b/arch/arm64/kvm/hypercalls.c @@ -31,7 +31,7 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu) val = SMCCC_RET_SUCCESS; break; case SPECTRE_UNAFFECTED: - val = SMCCC_RET_NOT_REQUIRED; + val = SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED; break; } break; diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h index 15c706fb0a37..0e50ba3e88d7 100644 --- a/include/linux/arm-smccc.h +++ b/include/linux/arm-smccc.h @@ -86,6 +86,8 @@ ARM_SMCCC_SMC_32, \ 0, 0x7fff) +#define SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED 1 + /* Paravirtualised time calls (defined by ARM DEN0057A) */ #define ARM_SMCCC_HV_PV_TIME_FEATURES \ ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
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 Cc: Andre Przywara <andre.przywara@arm.com> Cc: Steven Price <steven.price@arm.com> Cc: Marc Zyngier <maz@kernel.org> Cc: stable@vger.kernel.org Link: https://developer.arm.com/documentation/den0028/latest [1] Fixes: c118bbb52743 ("arm64: KVM: Propagate full Spectre v2 workaround state to KVM guests") Signed-off-by: Stephen Boyd <swboyd@chromium.org> --- I see that before commit c118bbb52743 ("arm64: KVM: Propagate full Spectre v2 workaround state to KVM guests") we had this mapping: 0 is SPECTRE_MITIGATED SMCCC_RET_NOT_SUPPORTED is SPECTRE_VULNERABLE so the return value '1' wasn't there then. Once the commit was merged we introduced the notion of NOT_REQUIRED here when it shouldn't have been introduced. Changes from v2: * Moved define to header file and used it Changes from v1: * Way longer commit text, more background (sorry) * Dropped proton-pack part because it was wrong * Rebased onto other patch accepted upstream arch/arm64/kernel/proton-pack.c | 2 -- arch/arm64/kvm/hypercalls.c | 2 +- include/linux/arm-smccc.h | 2 ++ 3 files changed, 3 insertions(+), 3 deletions(-) base-commit: 66dd3474702aa98d5844367e1577cdad78ef7c65