Re: [Qemu-arm] [PATCH RESEND v15 10/10] target-arm: kvm64: handle SIGBUS signal from kernel or KVM

[Peter Maydell]

On 8 November 2018 at 10:29, Dongjiu Geng <address@hidden> wrote:
> Add SIGBUS signal handler. In this handler, it checks the SIGBUS type,
> translates the host VA delivered by host to guest PA, then fill this PA
> to guest APEI GHES memory, then notify guest according to the SIGBUS type.
> There are two kinds of SIGBUS that QEMU needs to handle, which are
> BUS_MCEERR_AO and BUS_MCEERR_AR.
>
> If guest accesses the poisoned memory, it generates Synchronous External
> Abort(SEA). Then host kernel gets an APEI notification and call 
> memory_failure()
> to unmapped the affected page from the guest's stage 2, finally return
> to guest.
>
> Guest continues to access PG_hwpoison page, it will trap to KVM as stage2 
> fault,
> then a SIGBUS_MCEERR_AR synchronous signal is delivered to Qemu, Qemu record 
> this
> error into guest APEI GHES memory and notify guest using 
> Synchronous-External-Abort(SEA).
>
> Suggested-by: James Morse <address@hidden>
> Signed-off-by: Dongjiu Geng <address@hidden>
> ---
> Address James's comments to record CPER and notify guest for SIGBUS signal 
> handling.
> Shown some discussion in [1].
>
> [1]:
> https://lkml.org/lkml/2017/2/27/246
> https://lkml.org/lkml/2017/9/14/241
> https://lkml.org/lkml/2017/9/22/499
> ---

>
> +void kvm_arch_on_sigbus_vcpu(CPUState *c, int code, void *addr)
> +{
> +    ram_addr_t ram_addr;
> +    hwaddr paddr;
> +
> +    assert(code == BUS_MCEERR_AR || code == BUS_MCEERR_AO);
> +    if (addr) {
> +        ram_addr = qemu_ram_addr_from_host(addr);
> +        if (ram_addr != RAM_ADDR_INVALID &&
> +            kvm_physical_memory_addr_from_host(c->kvm_state, addr, &paddr)) {
> +            kvm_hwpoison_page_add(ram_addr);
> +            if (code == BUS_MCEERR_AR) {
> +                kvm_cpu_synchronize_state(c);
> +                if (ghes_record_errors(ACPI_HEST_NOTIFY_SEA, paddr)) {
> +                    kvm_inject_arm_sea(c);
> +                } else {
> +                    fprintf(stderr, "failed to record the error\n");
> +                }

Shouldn't there be something in here to say "only report this
error to the guest if we are actually reporting RAS errors
to the guest" ?

> +            }
> +            return;
> +        }
> +        fprintf(stderr, "Hardware memory error for memory used by "
> +                "QEMU itself instead of guest system!\n");
> +    }
> +
> +    if (code == BUS_MCEERR_AR) {
> +        fprintf(stderr, "Hardware memory error!\n");
> +        exit(1);
> +    }
> +}
> +
>  /* C6.6.29 BRK instruction */
>  static const uint32_t brk_insn = 0xd4200000;

thanks
-- PMM