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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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