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    SubjectRe: [PATCH 01/11] Add shared memory hypercall to PV Linux guest.
    On Mon, Nov 02, 2009 at 02:18:54PM +0200, Avi Kivity wrote:
    > On 11/01/2009 01:56 PM, Gleb Natapov wrote:
    > >Add hypercall that allows guest and host to setup per cpu shared
    > >memory.
    > >
    >
    > Better to set this up as an MSR (with bit zero enabling, bits 1-5
    > features, and 64-byte alignment). This allows auto-reset on INIT
    > and live migration using the existing MSR save/restore
    > infrastructure.
    >
    Hmm. Will do.

    > > arch/x86/include/asm/kvm_host.h | 3 +
    > > arch/x86/include/asm/kvm_para.h | 11 +++++
    > > arch/x86/kernel/kvm.c | 82 +++++++++++++++++++++++++++++++++++++++
    > > arch/x86/kernel/setup.c | 1 +
    > > arch/x86/kernel/smpboot.c | 3 +
    > > arch/x86/kvm/x86.c | 70 +++++++++++++++++++++++++++++++++
    > > include/linux/kvm.h | 1 +
    > > include/linux/kvm_para.h | 4 ++
    > > 8 files changed, 175 insertions(+), 0 deletions(-)
    >
    > Please separate into guest and host patches.
    >
    OK.

    > >+#define KVM_PV_SHM_VERSION 1
    >
    > versions = bad, feature bits = good
    >
    I have both! Do you want me to drop version?

    > >+
    > >+#define KVM_PV_SHM_FEATURES_ASYNC_PF (1<< 0)
    > >+
    > >+struct kvm_vcpu_pv_shm {
    > >+ __u64 features;
    > >+ __u64 reason;
    > >+ __u64 param;
    > >+};
    > >+
    >
    > Some documentation for this?
    >
    > Also, the name should reflect the pv pagefault use. For other uses
    > we can register other areas.
    >
    I wanted it to be generic, but I am fine with making it apf specific.
    It will allow to make it smaller too.

    > > #define MMU_QUEUE_SIZE 1024
    > >
    > >@@ -37,6 +41,7 @@ struct kvm_para_state {
    > > };
    > >
    > > static DEFINE_PER_CPU(struct kvm_para_state, para_state);
    > >+static DEFINE_PER_CPU(struct kvm_vcpu_pv_shm *, kvm_vcpu_pv_shm);
    >
    > Easier to put the entire structure here, not a pointer.
    OK.

    >
    > >+
    > >+static int kvm_pv_reboot_notify(struct notifier_block *nb,
    > >+ unsigned long code, void *unused)
    > >+{
    > >+ if (code == SYS_RESTART)
    > >+ on_each_cpu(kvm_pv_unregister_shm, NULL, 1);
    > >+ return NOTIFY_DONE;
    > >+}
    > >+
    > >+static struct notifier_block kvm_pv_reboot_nb = {
    > >+ .notifier_call = kvm_pv_reboot_notify,
    > >+};
    >
    > Is this called on kexec, or do we need another hook?
    >
    This was added specifically for kexec to work. It was called in my test,

    > >+static int kvm_pv_setup_shm(struct kvm_vcpu *vcpu, unsigned long gpa,
    > >+ unsigned long size, unsigned long version,
    > >+ unsigned long *ret)
    > >+{
    > >+ addr = gfn_to_hva(vcpu->kvm, gfn);
    > >+ if (kvm_is_error_hva(addr))
    > >+ return -EFAULT;
    > >+
    > >+ /* pin page with pv shared memory */
    > >+ down_read(&mm->mmap_sem);
    > >+ r = get_user_pages(current, mm, addr, 1, 1, 0,&vcpu->arch.pv_shm_page,
    > >+ NULL);
    > >+ up_read(&mm->mmap_sem);
    >
    > This fails if the memory area straddles a page boundary. Aligning
    Good point.

    > would solve this. I prefer using put_user() though than a permanent
    > get_user_pages().
    >
    I want to prevent it from been swapped out.

    --
    Gleb.


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