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Re: [Qemu-devel] [PATCH 2/3] s390: clear registers, psw and prefix at vc


From: Peter Maydell
Subject: Re: [Qemu-devel] [PATCH 2/3] s390: clear registers, psw and prefix at vcpu reset
Date: Fri, 23 Nov 2012 15:02:46 +0000

On 23 November 2012 10:18, Jens Freimann <address@hidden> wrote:
> +    /* The initial reset call is needed here to reset in-kernel
> +     * vcpu data that we can't access directly from QEMU.

If there's in-kernel vcpu data we can't access from QEMU,
doesn't this cause problems for migration?

> Before
> +     * this ioctl cpu_synchronize_state() is called in common kvm
> +     * code (kvm-all). What remains is clearing registers and psw
> +     * in QEMU cpu state */
> +    if (kvm_vcpu_ioctl(env, KVM_S390_INITIAL_RESET, NULL)) {
> +        perror("Can't reset vcpu\n");
> +    }

Doesn't this mean we're now out-of-sync again, since the
kernel state will be whatever INITIAL_RESET says it should
be but the QEMU state won't have been changed?

Generally, I think an arch-independent 'reset vcpu' ioctl
would be useful. At the moment for ARM you have to pull
everything out and back in again via the GET/SET_REG interface,
which works [you can keep all the state around to write back
on vcpu reset] but is ugly.

-- PMM



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