Re: [RESEND PATCH v21 5/6] target-arm: kvm64: handle SIGBUS signal from kernel or KVM

[Beata Michalska <beata.michalska@linaro.org>]

On Wed, 27 Nov 2019 at 13:03, Igor Mammedov <imammedo@redhat.com> wrote:
>
> On Wed, 27 Nov 2019 20:47:15 +0800
> Xiang Zheng <zhengxiang9@huawei.com> wrote:
>
> > Hi Beata,
> >
> > Thanks for you review!
> >
> > On 2019/11/22 23:47, Beata Michalska wrote:
> > > Hi,
> > >
> > > On Mon, 11 Nov 2019 at 01:48, Xiang Zheng <zhengxiang9@huawei.com> wrote:
> > >>
> > >> From: Dongjiu Geng <gengdongjiu@huawei.com>
> > >>
> > >> Add a SIGBUS signal handler. In this handler, it checks the SIGBUS type,
> > >> translates the host VA delivered by host to guest PA, then fills this PA
> > >> to guest APEI GHES memory, then notifies guest according to the SIGBUS
> > >> type.
> > >>
> > >> When guest accesses the poisoned memory, it will generate a Synchronous
> > >> External Abort(SEA). Then host kernel gets an APEI notification and calls
> > >> memory_failure() to unmapped the affected page in stage 2, finally
> > >> returns to guest.
> > >>
> > >> Guest continues to access the PG_hwpoison page, it will trap to KVM as
> > >> stage2 fault, then a SIGBUS_MCEERR_AR synchronous signal is delivered to
> > >> Qemu, Qemu records this error address into guest APEI GHES memory and
> > >> notifes guest using Synchronous-External-Abort(SEA).
> > >>
> > >> In order to inject a vSEA, we introduce the kvm_inject_arm_sea() function
> > >> in which we can setup the type of exception and the syndrome information.
> > >> When switching to guest, the target vcpu will jump to the synchronous
> > >> external abort vector table entry.
> > >>
> > >> The ESR_ELx.DFSC is set to synchronous external abort(0x10), and the
> > >> ESR_ELx.FnV is set to not valid(0x1), which will tell guest that FAR is
> > >> not valid and hold an UNKNOWN value. These values will be set to KVM
> > >> register structures through KVM_SET_ONE_REG IOCTL.
> > >>
> > >> Signed-off-by: Dongjiu Geng <gengdongjiu@huawei.com>
> > >> Signed-off-by: Xiang Zheng <zhengxiang9@huawei.com>
> > >> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> > >> ---
> [...]
> > >> diff --git a/include/hw/acpi/acpi_ghes.h b/include/hw/acpi/acpi_ghes.h
> > >> index cb62ec9c7b..8e3c5b879e 100644
> > >> --- a/include/hw/acpi/acpi_ghes.h
> > >> +++ b/include/hw/acpi/acpi_ghes.h
> > >> @@ -24,6 +24,9 @@
> > >>
> > >>  #include "hw/acpi/bios-linker-loader.h"
> > >>
> > >> +#define ACPI_GHES_CPER_OK                   1
> > >> +#define ACPI_GHES_CPER_FAIL                 0
> > >> +
> > >
> > > Is there really a need to introduce those ?
> > >
> >
> > Don't you think it's more clear than using "1" or "0"? :)
>
> or maybe just reuse default libc return convention: 0 - ok, -1 - fail
> and drop custom macros
>

Totally agree.

BR
Beata
> >
> > >>  /*
> > >>   * Values for Hardware Error Notification Type field
> > >>   */
> [...]
>