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Message-ID: <YxjaAI0i4czLuL4L@google.com>
Date: Wed, 7 Sep 2022 10:50:56 -0700
From: David Matlack <dmatlack@...gle.com>
To: Hou Wenlong <houwenlong.hwl@...group.com>
Cc: kvm@...r.kernel.org, Sean Christopherson <seanjc@...gle.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
"H. Peter Anvin" <hpa@...or.com>,
Lan Tianyu <Tianyu.Lan@...rosoft.com>,
linux-kernel@...r.kernel.org
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 <houwenlong.hwl@...group.com>
> ---
> 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
>
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