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[Qemu-devel] Re: [COMMIT bd83677] Fake dirty loggin when it's not there
From: |
Jan Kiszka |
Subject: |
[Qemu-devel] Re: [COMMIT bd83677] Fake dirty loggin when it's not there |
Date: |
Wed, 22 Jul 2009 19:00:48 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
Anthony Liguori wrote:
> From: Alexander Graf <address@hidden>
>
> Some KVM platforms don't support dirty logging yet, like IA64 and PPC,
> so in order to still have screen updates on those, we need to fake it.
>
> This patch just tells the getter function for dirty bitmaps, that all
> pages within a slot are dirty when the slot has dirty logging enabled.
>
> That way we can implement dirty logging on those platforms sometime when
> it drags down performance, but share the rest of the code with dirty
> logging capable platforms.
Sorry to disturb the merge, but my remarks remained unpatched. Would be
nice if they are considered in some follow-up patch... :)
>
> Signed-off-by: Alexander Graf <address@hidden>
> Signed-off-by: Anthony Liguori <aliguori-r/address@hidden>
>
> diff --git a/kvm-all.c b/kvm-all.c
> index 961fa32..2032949 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -300,6 +300,7 @@ int kvm_physical_sync_dirty_bitmap(target_phys_addr_t
> start_addr,
> KVMDirtyLog d;
> KVMSlot *mem;
> int ret = 0;
> + int r;
>
> d.dirty_bitmap = NULL;
> while (start_addr < end_addr) {
> @@ -308,6 +309,11 @@ int kvm_physical_sync_dirty_bitmap(target_phys_addr_t
> start_addr,
> break;
> }
>
> + /* We didn't activate dirty logging? Don't care then. */
> + if(!(mem->flags & KVM_MEM_LOG_DIRTY_PAGES)) {
> + continue;
> + }
> +
According to Alex' reply [1], I think this is probably better expressed
as an assert() than a silent skip. It indicates an error at higher
level, no?
> size = ((mem->memory_size >> TARGET_PAGE_BITS) + 7) / 8;
> if (!d.dirty_bitmap) {
> d.dirty_bitmap = qemu_malloc(size);
> @@ -319,7 +325,8 @@ int kvm_physical_sync_dirty_bitmap(target_phys_addr_t
> start_addr,
>
> d.slot = mem->slot;
>
> - if (kvm_vm_ioctl(s, KVM_GET_DIRTY_LOG, &d) == -1) {
> + r = kvm_vm_ioctl(s, KVM_GET_DIRTY_LOG, &d);
> + if (r == -EINVAL) {
> dprintf("ioctl failed %d\n", errno);
> ret = -1;
> break;
My remark still stands: This is an "optimistic" assumption that only
EINVAL is a "real" error. If KVM is buggy /wrt a specific invalid return
value, work around that particular bug (and we should also fix the
kernel, but that's a different topic).
Jan
[1] http://permalink.gmane.org/gmane.comp.emulators.qemu/47996
- [Qemu-devel] Re: [COMMIT bd83677] Fake dirty loggin when it's not there,
Jan Kiszka <=
- Re: [Qemu-devel] Re: [COMMIT bd83677] Fake dirty loggin when it's not there, Anthony Liguori, 2009/07/22
- [Qemu-devel] [PATCH] kvm: Fix error detection for KVM_GET_DIRTY_LOG, Jan Kiszka, 2009/07/22
- [Qemu-devel] Re: [PATCH] kvm: Fix error detection for KVM_GET_DIRTY_LOG, Anthony Liguori, 2009/07/22
- [Qemu-devel] Re: [PATCH] kvm: Fix error detection for KVM_GET_DIRTY_LOG, Jan Kiszka, 2009/07/22
- [Qemu-devel] Re: [PATCH] kvm: Fix error detection for KVM_GET_DIRTY_LOG, Anthony Liguori, 2009/07/22
- [Qemu-devel] Re: [PATCH] kvm: Fix error detection for KVM_GET_DIRTY_LOG, Jan Kiszka, 2009/07/22
- [Qemu-devel] Re: [PATCH] kvm: Fix error detection for KVM_GET_DIRTY_LOG, Alexander Graf, 2009/07/22
- [Qemu-devel] Re: [PATCH] kvm: Fix error detection for KVM_GET_DIRTY_LOG, Jan Kiszka, 2009/07/22
- [Qemu-devel] Re: [PATCH] kvm: Fix error detection for KVM_GET_DIRTY_LOG, Alexander Graf, 2009/07/22
- [Qemu-devel] Re: [PATCH] kvm: Fix error detection for KVM_GET_DIRTY_LOG, Anthony Liguori, 2009/07/22