On Wednesday 16 December 2015 03:10 PM, Thomas Huth wrote: > On 16/12/15 06:56, Aravinda Prasad wrote: >> This patch modifies KVM to cause a guest exit with >> KVM_EXIT_NMI instead of immediately delivering a 0x200 >> interrupt to guest upon machine check exception in >> guest address. Exiting the guest enables QEMU to build >> error log and deliver machine check exception to guest >> OS (either via guest OS registered machine check >> handler or via 0x200 guest OS interrupt vector). >> >> This approach simplifies the delivering of machine >> check exception to guest OS compared to the earlier approach >> of KVM directly invoking 0x200 guest interrupt vector. >> In the earlier approach QEMU patched the 0x200 interrupt >> vector during boot. The patched code at 0x200 issued a >> private hcall to pass the control to QEMU to build the >> error log. >> >> This design/approach is based on the feedback for the >> QEMU patches to handle machine check exception. Details >> of earlier approach of handling machine check exception >> in QEMU and related discussions can be found at: >> >> https://lists.nongnu.org/archive/html/qemu-devel/2014-11/msg00813.html >> >> This patch also introduces a new KVM capability to >> control how KVM behaves on machine check exception. >> Without this capability, KVM redirects machine check >> exceptions to guest's 0x200 vector if the address in >> error belongs to guest. With this capability KVM >> causes a guest exit with NMI exit reason. >> >> This is required to avoid problems if a new kernel/KVM >> is used with an old QEMU for guests that don't issue >> "ibm,nmi-register". As old QEMU does not understand the >> NMI exit type, it treats it as a fatal error. However, >> the guest could have handled the machine check error >> if the exception was delivered to guest's 0x200 interrupt >> vector instead of NMI exit in case of old QEMU. >> >> Change Log v2: >> - Added KVM capability >> >> Signed-off-by: Aravinda Prasad <aravinda@xxxxxxxxxxxxxxxxxx> >> --- >> arch/powerpc/include/asm/kvm_host.h | 1 + >> arch/powerpc/kernel/asm-offsets.c | 1 + >> arch/powerpc/kvm/book3s_hv.c | 12 +++------- >> arch/powerpc/kvm/book3s_hv_rmhandlers.S | 37 +++++++++++++++---------------- >> arch/powerpc/kvm/powerpc.c | 7 ++++++ >> include/uapi/linux/kvm.h | 1 + >> 6 files changed, 31 insertions(+), 28 deletions(-) >> >> diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h >> index 827a38d..8a652ba 100644 >> --- a/arch/powerpc/include/asm/kvm_host.h >> +++ b/arch/powerpc/include/asm/kvm_host.h >> @@ -243,6 +243,7 @@ struct kvm_arch { >> int hpt_cma_alloc; >> struct dentry *debugfs_dir; >> struct dentry *htab_dentry; >> + u8 fwnmi_enabled; > > Here you declare the variable as 8-bits ... > >> #endif /* CONFIG_KVM_BOOK3S_HV_POSSIBLE */ >> #ifdef CONFIG_KVM_BOOK3S_PR_POSSIBLE >> struct mutex hpt_mutex; >> diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c >> index 221d584..6a4e81a 100644 >> --- a/arch/powerpc/kernel/asm-offsets.c >> +++ b/arch/powerpc/kernel/asm-offsets.c >> @@ -506,6 +506,7 @@ int main(void) >> DEFINE(KVM_ENABLED_HCALLS, offsetof(struct kvm, arch.enabled_hcalls)); >> DEFINE(KVM_LPCR, offsetof(struct kvm, arch.lpcr)); >> DEFINE(KVM_VRMA_SLB_V, offsetof(struct kvm, arch.vrma_slb_v)); >> + DEFINE(KVM_FWNMI, offsetof(struct kvm, arch.fwnmi_enabled)); > > ... then define an asm-offset for it ... > >> DEFINE(VCPU_DSISR, offsetof(struct kvm_vcpu, arch.shregs.dsisr)); >> DEFINE(VCPU_DAR, offsetof(struct kvm_vcpu, arch.shregs.dar)); >> DEFINE(VCPU_VPA, offsetof(struct kvm_vcpu, arch.vpa.pinned_addr)); >> diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S >> index b98889e..f43c124 100644 >> --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S >> +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S > [...] >> @@ -2381,24 +2377,27 @@ machine_check_realmode: >> ld r9, HSTATE_KVM_VCPU(r13) >> li r12, BOOK3S_INTERRUPT_MACHINE_CHECK >> /* >> - * Deliver unhandled/fatal (e.g. UE) MCE errors to guest through >> - * machine check interrupt (set HSRR0 to 0x200). And for handled >> - * errors (no-fatal), just go back to guest execution with current >> - * HSRR0 instead of exiting guest. This new approach will inject >> - * machine check to guest for fatal error causing guest to crash. >> - * >> - * The old code used to return to host for unhandled errors which >> - * was causing guest to hang with soft lockups inside guest and >> - * makes it difficult to recover guest instance. >> + * Deliver unhandled/fatal (e.g. UE) MCE errors to guest >> + * by exiting the guest with KVM_EXIT_NMI exit reason (exit >> + * reason set later based on trap). For handled errors >> + * (no-fatal), go back to guest execution with current HSRR0 >> + * instead of exiting the guest. This approach will cause >> + * the guest to exit in case of fatal machine check error. >> */ >> - ld r10, VCPU_PC(r9) >> - ld r11, VCPU_MSR(r9) >> - bne 2f /* Continue guest execution. */ >> - /* If not, deliver a machine check. SRR0/1 are already set */ >> - li r10, BOOK3S_INTERRUPT_MACHINE_CHECK >> + bne 2f /* Continue guest execution? */ >> + /* If not, check if guest is capable of handling NMI exit */ >> + ld r3, VCPU_KVM(r9) >> + ld r3, KVM_FWNMI(r3) >> + cmpdi r3, 1 /* FWNMI capable? */ > > ... and here you're accessing the 8-bit variable with "ld" and "cmpdi"! > Is this really working as expected? Or did I miss something? Did you > check your code on both, little and big endian hosts? Ah... I should have used lbz Regards, Aravinda > > Thomas > > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@xxxxxxxxxxxxxxxx > https://lists.ozlabs.org/listinfo/linuxppc-dev > -- Regards, Aravinda -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
