From: Sean Christopherson <seanjc@google.com>
To: Ben Gardon <bgardon@google.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>, Peter Xu <peterx@redhat.com>,
David Matlack <dmatlack@google.com>,
Jim Mattson <jmattson@google.com>,
David Dunn <daviddunn@google.com>,
Jing Zhang <jingzhangos@google.com>,
Junaid Shahid <junaids@google.com>
Subject: Re: [PATCH v2 8/9] KVM: x86/mmu: Make kvm_is_mmio_pfn usable outside of spte.c
Date: Tue, 12 Apr 2022 19:39:07 +0000 [thread overview]
Message-ID: <YlXVW/qma/w50Y89@google.com> (raw)
In-Reply-To: <20220321224358.1305530-9-bgardon@google.com>
On Mon, Mar 21, 2022, Ben Gardon wrote:
> Export kvm_is_mmio_pfn from spte.c. It will be used in a subsequent
> commit for in-place lpage promotion when disabling dirty logging.
Rather than force the promotion path to call kvm_is_mmio_pfn(), what about:
a. Truly exporting the helper, i.e. EXPORT_SYMBOL_GPL
b. Move this patch earlier in the series, before "KVM: x86/mmu: Factor out part of
vmx_get_mt_mask which does not depend on vcpu"
c. In the same patch, drop the "is_mmio" param from kvm_x86_ops.get_mt_mask()
and have vmx_get_mt_mask() call it directly.
That way the call to kvm_is_mmio_pfn() is avoided when running on AMD hosts
(ignoring the shadow_me_mask thing, which I have a separate tweak for). The
worst case scenario for a lookup is actually quite expensive, e.g. retpoline and
a spinlock.
> Signed-off-by: Ben Gardon <bgardon@google.com>
> ---
> arch/x86/kvm/mmu/spte.c | 2 +-
> arch/x86/kvm/mmu/spte.h | 1 +
> 2 files changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c
> index 45e9c0c3932e..8e9b827c4ed5 100644
> --- a/arch/x86/kvm/mmu/spte.c
> +++ b/arch/x86/kvm/mmu/spte.c
> @@ -69,7 +69,7 @@ u64 make_mmio_spte(struct kvm_vcpu *vcpu, u64 gfn, unsigned int access)
> return spte;
> }
>
> -static bool kvm_is_mmio_pfn(kvm_pfn_t pfn)
> +bool kvm_is_mmio_pfn(kvm_pfn_t pfn)
> {
> if (pfn_valid(pfn))
> return !is_zero_pfn(pfn) && PageReserved(pfn_to_page(pfn)) &&
> diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h
> index cee02fe63429..e058a85e6c66 100644
> --- a/arch/x86/kvm/mmu/spte.h
> +++ b/arch/x86/kvm/mmu/spte.h
> @@ -443,4 +443,5 @@ u64 kvm_mmu_changed_pte_notifier_make_spte(u64 old_spte, kvm_pfn_t new_pfn);
>
> void kvm_mmu_reset_all_pte_masks(void);
>
> +bool kvm_is_mmio_pfn(kvm_pfn_t pfn);
> #endif
> --
> 2.35.1.894.gb6a874cedc-goog
>
next prev parent reply other threads:[~2022-04-12 19:41 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-21 22:43 [PATCH v2 0/9] KVM: x86/MMU: Optimize disabling dirty logging Ben Gardon
2022-03-21 22:43 ` [PATCH v2 1/9] KVM: x86/mmu: Move implementation of make_spte to a helper Ben Gardon
2022-03-21 22:43 ` [PATCH v2 2/9] KVM: x86/mmu: Factor mt_mask out of __make_spte Ben Gardon
2022-03-21 22:43 ` [PATCH v2 3/9] KVM: x86/mmu: Factor shadow_zero_check " Ben Gardon
2022-04-12 15:52 ` Sean Christopherson
2022-03-21 22:43 ` [PATCH v2 4/9] KVM: x86/mmu: Replace vcpu argument with kvm pointer in make_spte Ben Gardon
2022-03-21 22:43 ` [PATCH v2 5/9] KVM: x86/mmu: Factor out the meat of reset_tdp_shadow_zero_bits_mask Ben Gardon
2022-04-12 15:46 ` Sean Christopherson
2022-04-21 18:50 ` Ben Gardon
2022-04-21 19:09 ` Ben Gardon
2022-03-21 22:43 ` [PATCH v2 6/9] KVM: x86/mmu: Factor out part of vmx_get_mt_mask which does not depend on vcpu Ben Gardon
2022-03-28 18:04 ` David Matlack
2022-03-21 22:43 ` [PATCH v2 7/9] KVM: x86/mmu: Add try_get_mt_mask to x86_ops Ben Gardon
2022-04-11 23:00 ` Sean Christopherson
2022-04-11 23:24 ` Ben Gardon
2022-04-11 23:33 ` Sean Christopherson
2022-04-12 19:30 ` Sean Christopherson
2022-03-21 22:43 ` [PATCH v2 8/9] KVM: x86/mmu: Make kvm_is_mmio_pfn usable outside of spte.c Ben Gardon
2022-04-12 19:39 ` Sean Christopherson [this message]
2022-03-21 22:43 ` [PATCH v2 9/9] KVM: x86/mmu: Promote pages in-place when disabling dirty logging Ben Gardon
2022-03-28 17:45 ` David Matlack
2022-03-28 18:07 ` Ben Gardon
2022-03-28 18:20 ` David Matlack
2022-07-12 23:21 ` Sean Christopherson
2022-07-13 16:20 ` Sean Christopherson
2022-03-28 18:21 ` David Matlack
2022-04-12 16:43 ` Sean Christopherson
2022-04-25 18:09 ` Ben Gardon
2022-03-25 12:00 ` [PATCH v2 0/9] KVM: x86/MMU: Optimize " Paolo Bonzini
2022-07-12 1:37 ` Sean Christopherson
2022-07-14 7:55 ` Paolo Bonzini
2022-07-14 15:27 ` Sean Christopherson
2022-03-28 17:49 ` David Matlack
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