* [PATCH] KVM/x86: add comment to kvm_mmu_do_page_fault()
@ 2024-11-08 16:14 Juergen Gross
2024-12-19 2:40 ` Sean Christopherson
0 siblings, 1 reply; 2+ messages in thread
From: Juergen Gross @ 2024-11-08 16:14 UTC (permalink / raw)
To: linux-kernel, x86, kvm
Cc: Juergen Gross, Sean Christopherson, Paolo Bonzini,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen,
H. Peter Anvin
On a first glance it isn't obvious why calling kvm_tdp_page_fault() in
kvm_mmu_do_page_fault() is special cased, as the general case of using
an indirect case would result in calling of kvm_tdp_page_fault()
anyway.
Add a comment to explain the reason.
Signed-off-by: Juergen Gross <jgross@suse.com>
---
arch/x86/kvm/mmu/mmu_internal.h | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index c98827840e07..a49cd0c438a1 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -322,6 +322,10 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
fault.slot = kvm_vcpu_gfn_to_memslot(vcpu, fault.gfn);
}
+ /*
+ * With retpoline being active an indirect call is rather expensive,
+ * so do a direct call in the most common case.
+ */
if (IS_ENABLED(CONFIG_MITIGATION_RETPOLINE) && fault.is_tdp)
r = kvm_tdp_page_fault(vcpu, &fault);
else
--
2.43.0
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] KVM/x86: add comment to kvm_mmu_do_page_fault()
2024-11-08 16:14 [PATCH] KVM/x86: add comment to kvm_mmu_do_page_fault() Juergen Gross
@ 2024-12-19 2:40 ` Sean Christopherson
0 siblings, 0 replies; 2+ messages in thread
From: Sean Christopherson @ 2024-12-19 2:40 UTC (permalink / raw)
To: Sean Christopherson, linux-kernel, x86, kvm, Juergen Gross
Cc: Paolo Bonzini, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
Dave Hansen, H. Peter Anvin
On Fri, 08 Nov 2024 17:14:16 +0100, Juergen Gross wrote:
> On a first glance it isn't obvious why calling kvm_tdp_page_fault() in
> kvm_mmu_do_page_fault() is special cased, as the general case of using
> an indirect case would result in calling of kvm_tdp_page_fault()
> anyway.
>
> Add a comment to explain the reason.
>
> [...]
Applied to kvm-x86 mmu, thanks!
[1/1] KVM/x86: add comment to kvm_mmu_do_page_fault()
https://github.com/kvm-x86/linux/commit/2d5faa6a8402
--
https://github.com/kvm-x86/linux/tree/next
^ permalink raw reply [flat|nested] 2+ messages in thread
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2024-11-08 16:14 [PATCH] KVM/x86: add comment to kvm_mmu_do_page_fault() Juergen Gross
2024-12-19 2:40 ` Sean Christopherson
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