2021-10-22 01:01:27

by Sean Christopherson

Subject: [PATCH 1/3] KVM: x86/mmu: Drop a redundant, broken remote TLB flush

A recent commit to fix the calls to kvm_flush_remote_tlbs_with_address()
in kvm_zap_gfn_range() inadvertantly added yet another flush instead of
fixing the existing flush. Drop the redundant flush, and fix the params
for the existing flush.

Fixes: 2822da446640 ("KVM: x86/mmu: fix parameters to kvm_flush_remote_tlbs_with_address")
Cc: Maxim Levitsky <[email protected]>
Cc: Maciej S. Szmigiero <[email protected]>
Signed-off-by: Sean Christopherson <[email protected]>
---
arch/x86/kvm/mmu/mmu.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index c6ddb042b281..f82b192bba0b 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5709,13 +5709,11 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++)
flush = kvm_tdp_mmu_zap_gfn_range(kvm, i, gfn_start,
gfn_end, flush);
- if (flush)
- kvm_flush_remote_tlbs_with_address(kvm, gfn_start,
- gfn_end - gfn_start);
}

if (flush)
- kvm_flush_remote_tlbs_with_address(kvm, gfn_start, gfn_end);
+ kvm_flush_remote_tlbs_with_address(kvm, gfn_start,
+ gfn_end - gfn_start);

kvm_dec_notifier_count(kvm, gfn_start, gfn_end);

--
2.33.0.1079.g6e70778dc9-goog

2021-10-22 03:00:37

by Lai Jiangshan

Subject: Re: [PATCH 1/3] KVM: x86/mmu: Drop a redundant, broken remote TLB flush

On Fri, Oct 22, 2021 at 9:01 AM Sean Christopherson <[email protected]> wrote:
>
> A recent commit to fix the calls to kvm_flush_remote_tlbs_with_address()
> in kvm_zap_gfn_range() inadvertantly added yet another flush instead of
> fixing the existing flush. Drop the redundant flush, and fix the params
> for the existing flush.
>
> Fixes: 2822da446640 ("KVM: x86/mmu: fix parameters to kvm_flush_remote_tlbs_with_address")
> Cc: Maxim Levitsky <[email protected]>
> Cc: Maciej S. Szmigiero <[email protected]>
> Signed-off-by: Sean Christopherson <[email protected]>
> ---
> arch/x86/kvm/mmu/mmu.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index c6ddb042b281..f82b192bba0b 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -5709,13 +5709,11 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
> for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++)
> flush = kvm_tdp_mmu_zap_gfn_range(kvm, i, gfn_start,
> gfn_end, flush);
> - if (flush)
> - kvm_flush_remote_tlbs_with_address(kvm, gfn_start,
> - gfn_end - gfn_start);

In the recent queue branch of kvm tree, there is the same "if (flush)" in
the previous "if (kvm_memslots_have_rmaps(kvm))" branch. The "if (flush)"
branch needs to be removed too.

Reviewed-by: Lai Jiangshan <[email protected]>

> }
>
> if (flush)
> - kvm_flush_remote_tlbs_with_address(kvm, gfn_start, gfn_end);
> + kvm_flush_remote_tlbs_with_address(kvm, gfn_start,
> + gfn_end - gfn_start);
>
> kvm_dec_notifier_count(kvm, gfn_start, gfn_end);
>
> --
> 2.33.0.1079.g6e70778dc9-goog
>

2021-10-22 03:05:17

by Lai Jiangshan

Subject: Re: [PATCH 1/3] KVM: x86/mmu: Drop a redundant, broken remote TLB flush

On Fri, Oct 22, 2021 at 10:58 AM Lai Jiangshan
<[email protected]> wrote:
>
> On Fri, Oct 22, 2021 at 9:01 AM Sean Christopherson <[email protected]> wrote:
> >
> > A recent commit to fix the calls to kvm_flush_remote_tlbs_with_address()
> > in kvm_zap_gfn_range() inadvertantly added yet another flush instead of
> > fixing the existing flush. Drop the redundant flush, and fix the params
> > for the existing flush.
> >
> > Fixes: 2822da446640 ("KVM: x86/mmu: fix parameters to kvm_flush_remote_tlbs_with_address")
> > Cc: Maxim Levitsky <[email protected]>
> > Cc: Maciej S. Szmigiero <[email protected]>
> > Signed-off-by: Sean Christopherson <[email protected]>
> > ---
> > arch/x86/kvm/mmu/mmu.c | 6 ++----
> > 1 file changed, 2 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> > index c6ddb042b281..f82b192bba0b 100644
> > --- a/arch/x86/kvm/mmu/mmu.c
> > +++ b/arch/x86/kvm/mmu/mmu.c
> > @@ -5709,13 +5709,11 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
> > for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++)
> > flush = kvm_tdp_mmu_zap_gfn_range(kvm, i, gfn_start,
> > gfn_end, flush);
> > - if (flush)
> > - kvm_flush_remote_tlbs_with_address(kvm, gfn_start,
> > - gfn_end - gfn_start);
>
> In the recent queue branch of kvm tree, there is the same "if (flush)" in
> the previous "if (kvm_memslots_have_rmaps(kvm))" branch. The "if (flush)"
> branch needs to be removed too.

Oh, it is in the patch 2. For patch 1 and 2:

Reviewed-by: Lai Jiangshan <[email protected]>

>
> Reviewed-by: Lai Jiangshan <[email protected]>
>
> > }
> >
> > if (flush)
> > - kvm_flush_remote_tlbs_with_address(kvm, gfn_start, gfn_end);
> > + kvm_flush_remote_tlbs_with_address(kvm, gfn_start,
> > + gfn_end - gfn_start);
> >
> > kvm_dec_notifier_count(kvm, gfn_start, gfn_end);
> >
> > --
> > 2.33.0.1079.g6e70778dc9-goog
> >

2021-10-22 15:40:59

by Maxim Levitsky

Subject: Re: [PATCH 1/3] KVM: x86/mmu: Drop a redundant, broken remote TLB flush

On Thu, 2021-10-21 at 18:00 -0700, Sean Christopherson wrote:
> A recent commit to fix the calls to kvm_flush_remote_tlbs_with_address()
> in kvm_zap_gfn_range() inadvertantly added yet another flush instead of
> fixing the existing flush. Drop the redundant flush, and fix the params
> for the existing flush.
>
> Fixes: 2822da446640 ("KVM: x86/mmu: fix parameters to kvm_flush_remote_tlbs_with_address")
> Cc: Maxim Levitsky <[email protected]>
> Cc: Maciej S. Szmigiero <[email protected]>
> Signed-off-by: Sean Christopherson <[email protected]>
> ---
> arch/x86/kvm/mmu/mmu.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index c6ddb042b281..f82b192bba0b 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -5709,13 +5709,11 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
> for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++)
> flush = kvm_tdp_mmu_zap_gfn_range(kvm, i, gfn_start,
> gfn_end, flush);
> - if (flush)
> - kvm_flush_remote_tlbs_with_address(kvm, gfn_start,
> - gfn_end - gfn_start);
> }
>
> if (flush)
> - kvm_flush_remote_tlbs_with_address(kvm, gfn_start, gfn_end);
> + kvm_flush_remote_tlbs_with_address(kvm, gfn_start,
> + gfn_end - gfn_start);
>
> kvm_dec_notifier_count(kvm, gfn_start, gfn_end);
>
Opps, I didn't notice that the revert added back another flush. I probablyhaven't had
the revert in place when I wrote the patch that fixed parameters to
kvm_flush_remote_tlbs_with_address.

Best regards,
Maxim Levitsky