2022-08-24 10:10:31

by Hou Wenlong

Subject: [PATCH v2 2/6] KVM: x86/mmu: Fix wrong gfn range of tlb flushing in kvm_set_pte_rmapp()

When the spte of hupe page is dropped in kvm_set_pte_rmapp(),
the whole gfn range covered by the spte should be flushed.
However, rmap_walk_init_level() doesn't align down the gfn
for new level like tdp iterator does, then the gfn used in
kvm_set_pte_rmapp() is not the base gfn of huge page. And
the size of gfn range is wrong too for huge page. Use the
base gfn of huge page and the size of huge page for
flushing tlbs for huge page.

Fixes: c3134ce240eed ("KVM: Replace old tlb flush function with new one to flush a specified range.")
Signed-off-by: Hou Wenlong <[email protected]>
---
arch/x86/kvm/mmu/mmu.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index a3578abd8bbc..3bcff56df109 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -1438,7 +1438,8 @@ static bool kvm_set_pte_rmap(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
}

if (need_flush && kvm_available_flush_tlb_with_range()) {
- kvm_flush_remote_tlbs_with_address(kvm, gfn, 1);
+ kvm_flush_remote_tlbs_with_address(kvm, gfn & -KVM_PAGES_PER_HPAGE(level),
+ KVM_PAGES_PER_HPAGE(level));
return false;
}

--
2.31.1

2022-09-07 18:01:58

by David Matlack

Subject: Re: [PATCH v2 2/6] KVM: x86/mmu: Fix wrong gfn range of tlb flushing in kvm_set_pte_rmapp()

On Wed, Aug 24, 2022 at 05:29:19PM +0800, Hou Wenlong wrote:
> When the spte of hupe page is dropped in kvm_set_pte_rmapp(),
> the whole gfn range covered by the spte should be flushed.
> However, rmap_walk_init_level() doesn't align down the gfn
> for new level like tdp iterator does, then the gfn used in
> kvm_set_pte_rmapp() is not the base gfn of huge page. And
> the size of gfn range is wrong too for huge page. Use the
> base gfn of huge page and the size of huge page for
> flushing tlbs for huge page.
>
> Fixes: c3134ce240eed ("KVM: Replace old tlb flush function with new one to flush a specified range.")
> Signed-off-by: Hou Wenlong <[email protected]>
> ---
> arch/x86/kvm/mmu/mmu.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index a3578abd8bbc..3bcff56df109 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -1438,7 +1438,8 @@ static bool kvm_set_pte_rmap(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
> }
>
> if (need_flush && kvm_available_flush_tlb_with_range()) {
> - kvm_flush_remote_tlbs_with_address(kvm, gfn, 1);
> + kvm_flush_remote_tlbs_with_address(kvm, gfn & -KVM_PAGES_PER_HPAGE(level),

Rounding down the GFN to a huge page size is a common pattern throughout
KVM. Can you introduce a common way of doing this and clean up the other
call sites?

> + KVM_PAGES_PER_HPAGE(level));

This eventually gets converted to kvm_flush_remote_tlbs_gfn() in a later
patch; which is even more reason to introduce
kvm_flush_remote_tlbs_gfn() in the previous patch.

> return false;
> }
>
> --
> 2.31.1
>