On Wed, Jan 13, 2016 at 12:38:09PM +0530, Aravinda Prasad wrote: > Enhance KVM to cause a guest exit with KVM_EXIT_NMI > exit reasons upon a machine check exception (MCE) in > the guest address space if the KVM_CAP_PPC_FWNMI > capability is enabled (instead of delivering 0x200 > interrupt to guest). This enables QEMU to build error > log and deliver machine check exception to guest via > guest registered machine check handler. > > 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 was enhanced to > patch 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 > > Signed-off-by: Aravinda Prasad <aravi...@linux.vnet.ibm.com>
Reviewed-by: David Gibson <da...@gibson.dropbear.id.au>
> ---
> arch/powerpc/kvm/book3s_hv.c | 12 ++------
> arch/powerpc/kvm/book3s_hv_rmhandlers.S | 48
> +++++++++++++++----------------
> 2 files changed, 26 insertions(+), 34 deletions(-)
>
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index a7352b5..4fa03d0 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -858,15 +858,9 @@ static int kvmppc_handle_exit_hv(struct kvm_run *run,
> struct kvm_vcpu *vcpu,
> r = RESUME_GUEST;
> break;
> case BOOK3S_INTERRUPT_MACHINE_CHECK:
> - /*
> - * Deliver a machine check interrupt to the guest.
> - * We have to do this, even if the host has handled the
> - * machine check, because machine checks use SRR0/1 and
> - * the interrupt might have trashed guest state in them.
> - */
> - kvmppc_book3s_queue_irqprio(vcpu,
> - BOOK3S_INTERRUPT_MACHINE_CHECK);
> - r = RESUME_GUEST;
> + /* Exit to guest with KVM_EXIT_NMI as exit reason */
> + run->exit_reason = KVM_EXIT_NMI;
> + r = RESUME_HOST;
> break;
> case BOOK3S_INTERRUPT_PROGRAM:
> {
> diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> index 3c6badc..84e32a3 100644
> --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> @@ -133,21 +133,18 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
> stb r0, HSTATE_HWTHREAD_REQ(r13)
>
> /*
> - * For external and machine check interrupts, we need
> - * to call the Linux handler to process the interrupt.
> - * We do that by jumping to absolute address 0x500 for
> - * external interrupts, or the machine_check_fwnmi label
> - * for machine checks (since firmware might have patched
> - * the vector area at 0x200). The [h]rfid at the end of the
> - * handler will return to the book3s_hv_interrupts.S code.
> - * For other interrupts we do the rfid to get back
> - * to the book3s_hv_interrupts.S code here.
> + * For external interrupts we need to call the Linux
> + * handler to process the interrupt. We do that by jumping
> + * to absolute address 0x500 for external interrupts.
> + * The [h]rfid at the end of the handler will return to
> + * the book3s_hv_interrupts.S code. For other interrupts
> + * we do the rfid to get back to the book3s_hv_interrupts.S
> + * code here.
> */
> ld r8, 112+PPC_LR_STKOFF(r1)
> addi r1, r1, 112
> ld r7, HSTATE_HOST_MSR(r13)
>
> - cmpwi cr1, r12, BOOK3S_INTERRUPT_MACHINE_CHECK
> cmpwi r12, BOOK3S_INTERRUPT_EXTERNAL
> beq 11f
> cmpwi r12, BOOK3S_INTERRUPT_H_DOORBELL
> @@ -162,7 +159,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
> mtmsrd r6, 1 /* Clear RI in MSR */
> mtsrr0 r8
> mtsrr1 r7
> - beq cr1, 13f /* machine check */
> RFI
>
> /* On POWER7, we have external interrupts set to use HSRR0/1 */
> @@ -170,8 +166,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
> mtspr SPRN_HSRR1, r7
> ba 0x500
>
> -13: b machine_check_fwnmi
> -
> 14: mtspr SPRN_HSRR0, r8
> mtspr SPRN_HSRR1, r7
> b hmi_exception_after_realmode
> @@ -2390,15 +2384,13 @@ 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 either
> + * through machine check interrupt (set HSRR0 to 0x200) or by
> + * exiting the guest with KVM_EXIT_NMI exit reason if guest is
> + * FWNMI capable. For handled errors (no-fatal), just go back
> + * to guest execution with current HSRR0. This new approach
> + * injects machine check errors in guest address space to guest
> + * enabling guest kernel to suitably handle such errors.
> *
> * if we receive machine check with MSR(RI=0) then deliver it to
> * guest as machine check causing guest to crash.
> @@ -2408,11 +2400,17 @@ machine_check_realmode:
> beq 1f /* Deliver a machine check to guest */
> ld r10, VCPU_PC(r9)
> cmpdi r3, 0 /* Did we handle MCE ? */
> - bne 2f /* Continue guest execution. */
> + bne 3f /* Continue guest execution. */
> /* If not, deliver a machine check. SRR0/1 are already set */
> -1: li r10, BOOK3S_INTERRUPT_MACHINE_CHECK
> +1: /* Check if guest is capable of handling NMI exit */
> + ld r3, VCPU_KVM(r9)
> + lbz r3, KVM_FWNMI(r3)
> + cmpdi r3, 1 /* FWNMI capable? */
> + bne 2f
> + b mc_cont
> +2: li r10, BOOK3S_INTERRUPT_MACHINE_CHECK
> bl kvmppc_msr_interrupt
> -2: b fast_interrupt_c_return
> +3: b fast_interrupt_c_return
>
> /*
> * Check the reason we woke from nap, and take appropriate action.
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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