| Message ID | 1248691134-54120-1-git-send-email-agraf@suse.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
bump On 27.07.2009, at 12:38, Alexander Graf wrote: > We currently use host endian long types to store information > in the dirty bitmap. > > This works reasonably well on Little Endian targets, because the > u32 after the first contains the next 32 bits. On Big Endian this > breaks completely though, forcing us to be inventive here. > > So Ben suggested to always use Little Endian, which looks reasonable. > > We only have dirty bitmap implemented in Little Endian targets so far > and since PowerPC would be the first Big Endian platform, we can just > as well switch to Little Endian always with little effort without > breaking existing targets. > > Signed-off-by: Alexander Graf <agraf@suse.de> > --- > virt/kvm/kvm_main.c | 5 +++-- > 1 files changed, 3 insertions(+), 2 deletions(-) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 17d8688..3482ad1 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -48,6 +48,7 @@ > #include <asm/io.h> > #include <asm/uaccess.h> > #include <asm/pgtable.h> > +#include <asm-generic/bitops/le.h> > > #ifdef KVM_COALESCED_MMIO_PAGE_OFFSET > #include "coalesced_mmio.h" > @@ -1656,8 +1657,8 @@ void mark_page_dirty(struct kvm *kvm, gfn_t gfn) > unsigned long rel_gfn = gfn - memslot->base_gfn; > > /* avoid RMW */ > - if (!test_bit(rel_gfn, memslot->dirty_bitmap)) > - set_bit(rel_gfn, memslot->dirty_bitmap); > + if (!generic_test_le_bit(rel_gfn, memslot->dirty_bitmap)) > + generic___set_le_bit(rel_gfn, memslot->dirty_bitmap); > } > } > > -- > 1.6.0.2 > > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, 2009-07-27 at 12:38 +0200, Alexander Graf wrote: > We currently use host endian long types to store information > in the dirty bitmap. > > This works reasonably well on Little Endian targets, because the > u32 after the first contains the next 32 bits. On Big Endian this > breaks completely though, forcing us to be inventive here. > > So Ben suggested to always use Little Endian, which looks reasonable. > > We only have dirty bitmap implemented in Little Endian targets so far > and since PowerPC would be the first Big Endian platform, we can just > as well switch to Little Endian always with little effort without > breaking existing targets. > > Signed-off-by: Alexander Graf <agraf@suse.de> > --- > virt/kvm/kvm_main.c | 5 +++-- > 1 files changed, 3 insertions(+), 2 deletions(-) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 17d8688..3482ad1 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -48,6 +48,7 @@ > #include <asm/io.h> > #include <asm/uaccess.h> > #include <asm/pgtable.h> > +#include <asm-generic/bitops/le.h> > > #ifdef KVM_COALESCED_MMIO_PAGE_OFFSET > #include "coalesced_mmio.h" > @@ -1656,8 +1657,8 @@ void mark_page_dirty(struct kvm *kvm, gfn_t gfn) > unsigned long rel_gfn = gfn - memslot->base_gfn; > > /* avoid RMW */ > - if (!test_bit(rel_gfn, memslot->dirty_bitmap)) > - set_bit(rel_gfn, memslot->dirty_bitmap); > + if (!generic_test_le_bit(rel_gfn, memslot->dirty_bitmap)) > + generic___set_le_bit(rel_gfn, memslot->dirty_bitmap); > } > } I don't think I've ever exercised the dirty bitmap code, and I don't really have an opinion. Avi?
On 29.09.2009, at 02:08, Hollis Blanchard wrote: > On Mon, 2009-07-27 at 12:38 +0200, Alexander Graf wrote: >> We currently use host endian long types to store information >> in the dirty bitmap. >> >> This works reasonably well on Little Endian targets, because the >> u32 after the first contains the next 32 bits. On Big Endian this >> breaks completely though, forcing us to be inventive here. >> >> So Ben suggested to always use Little Endian, which looks reasonable. >> >> We only have dirty bitmap implemented in Little Endian targets so far >> and since PowerPC would be the first Big Endian platform, we can just >> as well switch to Little Endian always with little effort without >> breaking existing targets. >> >> Signed-off-by: Alexander Graf <agraf@suse.de> >> --- >> virt/kvm/kvm_main.c | 5 +++-- >> 1 files changed, 3 insertions(+), 2 deletions(-) >> >> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c >> index 17d8688..3482ad1 100644 >> --- a/virt/kvm/kvm_main.c >> +++ b/virt/kvm/kvm_main.c >> @@ -48,6 +48,7 @@ >> #include <asm/io.h> >> #include <asm/uaccess.h> >> #include <asm/pgtable.h> >> +#include <asm-generic/bitops/le.h> >> >> #ifdef KVM_COALESCED_MMIO_PAGE_OFFSET >> #include "coalesced_mmio.h" >> @@ -1656,8 +1657,8 @@ void mark_page_dirty(struct kvm *kvm, gfn_t >> gfn) >> unsigned long rel_gfn = gfn - memslot->base_gfn; >> >> /* avoid RMW */ >> - if (!test_bit(rel_gfn, memslot->dirty_bitmap)) >> - set_bit(rel_gfn, memslot->dirty_bitmap); >> + if (!generic_test_le_bit(rel_gfn, memslot->dirty_bitmap)) >> + generic___set_le_bit(rel_gfn, memslot->dirty_bitmap); >> } >> } > > I don't think I've ever exercised the dirty bitmap code, and I don't > really have an opinion. Avi? No big endian kvm target currently implements dirty bitmaps. In fact, IIRC only x86 does atm. So by pinning it to LE now, we save ourselves from much trouble for any later user. Alex -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 17d8688..3482ad1 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -48,6 +48,7 @@ #include <asm/io.h> #include <asm/uaccess.h> #include <asm/pgtable.h> +#include <asm-generic/bitops/le.h> #ifdef KVM_COALESCED_MMIO_PAGE_OFFSET #include "coalesced_mmio.h" @@ -1656,8 +1657,8 @@ void mark_page_dirty(struct kvm *kvm, gfn_t gfn) unsigned long rel_gfn = gfn - memslot->base_gfn; /* avoid RMW */ - if (!test_bit(rel_gfn, memslot->dirty_bitmap)) - set_bit(rel_gfn, memslot->dirty_bitmap); + if (!generic_test_le_bit(rel_gfn, memslot->dirty_bitmap)) + generic___set_le_bit(rel_gfn, memslot->dirty_bitmap); } }
We currently use host endian long types to store information in the dirty bitmap. This works reasonably well on Little Endian targets, because the u32 after the first contains the next 32 bits. On Big Endian this breaks completely though, forcing us to be inventive here. So Ben suggested to always use Little Endian, which looks reasonable. We only have dirty bitmap implemented in Little Endian targets so far and since PowerPC would be the first Big Endian platform, we can just as well switch to Little Endian always with little effort without breaking existing targets. Signed-off-by: Alexander Graf <agraf@suse.de> --- virt/kvm/kvm_main.c | 5 +++-- 1 files changed, 3 insertions(+), 2 deletions(-)