Re: [PATCH V4 7/15] KVM/MMU: Flush tlb directly in the kvm_zap_gfn_range()

[Tianyu Lan]

Hi Paolo:
  Thanks for your review.

On Mon, Oct 15, 2018 at 6:04 PM Paolo Bonzini  wrote:
>
> On 13/10/2018 16:53, lantianyu1...@gmail.com wrote:
> > + bool flush = false;
> >   int i;
> >
> >   spin_lock(>mmu_lock);
> > @@ -5654,18 +5655,27 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t 
> > gfn_start, gfn_t gfn_end)
> >   slots = __kvm_memslots(kvm, i);
> >   kvm_for_each_memslot(memslot, slots) {
> >   gfn_t start, end;
> > + bool flush_tlb = true;
> >
> >   start = max(gfn_start, memslot->base_gfn);
> >   end = min(gfn_end, memslot->base_gfn + 
> > memslot->npages);
> >   if (start >= end)
> >   continue;
> >
> > - slot_handle_level_range(kvm, memslot, kvm_zap_rmapp,
> > - PT_PAGE_TABLE_LEVEL, 
> > PT_MAX_HUGEPAGE_LEVEL,
> > - start, end - 1, true);
> > + if (kvm_available_flush_tlb_with_range())
> > + flush_tlb = false;
>
> This should be moved outside the for, because it's invariant.
>
> > + flush = slot_handle_level_range(kvm, memslot,
> > + kvm_zap_rmapp, PT_PAGE_TABLE_LEVEL,
> > + PT_MAX_HUGEPAGE_LEVEL, start,
> > + end - 1, flush_tlb);
>
> ... and this should be "flush |= ".
> >   }
> >   }
> >
> > + if (flush && kvm_available_flush_tlb_with_range())
> > + kvm_flush_remote_tlbs_with_address(kvm, gfn_start,
> > + gfn_end - gfn_start + 1);
> > +
>
> ... and this can be just if (flush), because if flush_tlb is true then
> slot_handle_level_range always returns false.

OK. Will update.

-- 
Best regards
Tianyu Lan
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Re: [PATCH V4 7/15] KVM/MMU: Flush tlb directly in the kvm_zap_gfn_range()

[Paolo Bonzini]

On 13/10/2018 16:53, lantianyu1...@gmail.com wrote:
> + bool flush = false;
>   int i;
>  
>   spin_lock(>mmu_lock);
> @@ -5654,18 +5655,27 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t 
> gfn_start, gfn_t gfn_end)
>   slots = __kvm_memslots(kvm, i);
>   kvm_for_each_memslot(memslot, slots) {
>   gfn_t start, end;
> + bool flush_tlb = true;
>  
>   start = max(gfn_start, memslot->base_gfn);
>   end = min(gfn_end, memslot->base_gfn + memslot->npages);
>   if (start >= end)
>   continue;
>  
> - slot_handle_level_range(kvm, memslot, kvm_zap_rmapp,
> - PT_PAGE_TABLE_LEVEL, 
> PT_MAX_HUGEPAGE_LEVEL,
> - start, end - 1, true);
> + if (kvm_available_flush_tlb_with_range())
> + flush_tlb = false;

This should be moved outside the for, because it's invariant.

> + flush = slot_handle_level_range(kvm, memslot,
> + kvm_zap_rmapp, PT_PAGE_TABLE_LEVEL,
> + PT_MAX_HUGEPAGE_LEVEL, start,
> + end - 1, flush_tlb);

... and this should be "flush |= ".
>   }
>   }
>  
> + if (flush && kvm_available_flush_tlb_with_range())
> + kvm_flush_remote_tlbs_with_address(kvm, gfn_start,
> + gfn_end - gfn_start + 1);
> +

... and this can be just if (flush), because if flush_tlb is true then
slot_handle_level_range always returns false.

Paolo
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[PATCH V4 7/15] KVM/MMU: Flush tlb directly in the kvm_zap_gfn_range()

[lantianyu1986]

From: Lan Tianyu 

Originally, flush tlb is done by slot_handle_level_range(). This patch
is to flush tlb directly in the kvm_zap_gfn_range() when range
flush is available.

Signed-off-by: Lan Tianyu 
---
 arch/x86/kvm/mmu.c | 16 +---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index f3742ff4ec18..c4f7679f12c3 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -5647,6 +5647,7 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, 
gfn_t gfn_end)
 {
struct kvm_memslots *slots;
struct kvm_memory_slot *memslot;
+   bool flush = false;
int i;
 
spin_lock(>mmu_lock);
@@ -5654,18 +5655,27 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t 
gfn_start, gfn_t gfn_end)
slots = __kvm_memslots(kvm, i);
kvm_for_each_memslot(memslot, slots) {
gfn_t start, end;
+   bool flush_tlb = true;
 
start = max(gfn_start, memslot->base_gfn);
end = min(gfn_end, memslot->base_gfn + memslot->npages);
if (start >= end)
continue;
 
-   slot_handle_level_range(kvm, memslot, kvm_zap_rmapp,
-   PT_PAGE_TABLE_LEVEL, 
PT_MAX_HUGEPAGE_LEVEL,
-   start, end - 1, true);
+   if (kvm_available_flush_tlb_with_range())
+   flush_tlb = false;
+
+   flush = slot_handle_level_range(kvm, memslot,
+   kvm_zap_rmapp, PT_PAGE_TABLE_LEVEL,
+   PT_MAX_HUGEPAGE_LEVEL, start,
+   end - 1, flush_tlb);
}
}
 
+   if (flush && kvm_available_flush_tlb_with_range())
+   kvm_flush_remote_tlbs_with_address(kvm, gfn_start,
+   gfn_end - gfn_start + 1);
+
spin_unlock(>mmu_lock);
 }
 
-- 
2.14.4

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