linux-kernel - [PATCH 2/3] KVM: x86/mmu: Open code GFN "rounding" in TDP MMU

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Message-Id: <20201027214300.1342-3-sean.j.christopherson@intel.com>
Date:   Tue, 27 Oct 2020 14:42:59 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Ben Gardon <bgardon@...gle.com>
Subject: [PATCH 2/3] KVM: x86/mmu: Open code GFN "rounding" in TDP MMU

Drop round_gfn_for_level() and directly use the recently introdocued
KVM_HPAGE_GFN_MASK() macro.  Hiding the masking in a "rounding" function
adds an extra "what does this do?" lookup, whereas the concept and usage
of PFN/GFN masks is common enough that it's easy to read the open coded
version without thinking too hard.

No functional change intended.

Cc: Ben Gardon <bgardon@...gle.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kvm/mmu/tdp_iter.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/mmu/tdp_iter.c b/arch/x86/kvm/mmu/tdp_iter.c
index c6e914c96641..4175947dc401 100644
--- a/arch/x86/kvm/mmu/tdp_iter.c
+++ b/arch/x86/kvm/mmu/tdp_iter.c
@@ -15,11 +15,6 @@ static void tdp_iter_refresh_sptep(struct tdp_iter *iter)
 	iter->old_spte = READ_ONCE(*iter->sptep);
 }
 
-static gfn_t round_gfn_for_level(gfn_t gfn, int level)
-{
-	return gfn & KVM_HPAGE_GFN_MASK(level);
-}
-
 /*
  * Sets a TDP iterator to walk a pre-order traversal of the paging structure
  * rooted at root_pt, starting with the walk to translate goal_gfn.
@@ -36,7 +31,7 @@ void tdp_iter_start(struct tdp_iter *iter, u64 *root_pt, int root_level,
 	iter->level = root_level;
 	iter->pt_path[iter->level - 1] = root_pt;
 
-	iter->gfn = round_gfn_for_level(iter->goal_gfn, iter->level);
+	iter->gfn = iter->goal_gfn & KVM_HPAGE_GFN_MASK(iter->level);
 	tdp_iter_refresh_sptep(iter);
 
 	iter->valid = true;
@@ -82,7 +77,7 @@ static bool try_step_down(struct tdp_iter *iter)
 
 	iter->level--;
 	iter->pt_path[iter->level - 1] = child_pt;
-	iter->gfn = round_gfn_for_level(iter->goal_gfn, iter->level);
+	iter->gfn = iter->goal_gfn & KVM_HPAGE_GFN_MASK(iter->level);
 	tdp_iter_refresh_sptep(iter);
 
 	return true;
@@ -124,7 +119,7 @@ static bool try_step_up(struct tdp_iter *iter)
 		return false;
 
 	iter->level++;
-	iter->gfn = round_gfn_for_level(iter->gfn, iter->level);
+	iter->gfn &= KVM_HPAGE_GFN_MASK(iter->level);
 	tdp_iter_refresh_sptep(iter);
 
 	return true;
-- 
2.28.0