From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Marc Zyngier <maz@kernel.org>, Paul Mackerras <paulus@ozlabs.org>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Janosch Frank <frankja@linux.ibm.com>,
Paolo Bonzini <pbonzini@redhat.com>
Cc: James Morse <james.morse@arm.com>,
Julien Thierry <julien.thierry.kdev@gmail.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
David Hildenbrand <david@redhat.com>,
Cornelia Huck <cohuck@redhat.com>,
Claudio Imbrenda <imbrenda@linux.ibm.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org,
kvm@vger.kernel.org, kvm-ppc@vger.kernel.org,
linux-kernel@vger.kernel.org, Peter Feiner <pfeiner@google.com>,
Peter Shier <pshier@google.com>,
Junaid Shahid <junaids@google.com>,
Ben Gardon <bgardon@google.com>,
Christoffer Dall <christoffer.dall@arm.com>
Subject: [PATCH 08/21] KVM: x86/mmu: Clean up the gorilla math in mmu_topup_memory_caches()
Date: Fri, 5 Jun 2020 14:38:40 -0700 [thread overview]
Message-ID: <20200605213853.14959-9-sean.j.christopherson@intel.com> (raw)
In-Reply-To: <20200605213853.14959-1-sean.j.christopherson@intel.com>
Clean up the minimums in mmu_topup_memory_caches() to document the
driving mechanisms behind the minimums. Now that encountering an empty
cache is unlikely to trigger BUG_ON(), it is less dangerous to be more
precise when defining the minimums.
For rmaps, the logic is 1 parent PTE per level, plus a single rmap, and
prefetched rmaps. The extra objects in the current '8 + PREFETCH'
minimum came about due to an abundance of paranoia in commit
c41ef344de212 ("KVM: MMU: increase per-vcpu rmap cache alloc size"),
i.e. it could have increased the minimum to 2 rmaps. Furthermore, the
unexpected extra rmap case was killed off entirely by commits
f759e2b4c728c ("KVM: MMU: avoid pte_list_desc running out in
kvm_mmu_pte_write") and f5a1e9f89504f ("KVM: MMU: remove call to
kvm_mmu_pte_write from walk_addr").
For the so called page cache, replace '8' with 2*PT64_ROOT_MAX_LEVEL.
The 2x multiplier is needed because the cache is used for both shadow
pages and gfn arrays for indirect MMUs.
And finally, for page headers, replace '4' with PT64_ROOT_MAX_LEVEL.
Note, KVM now supports 5-level paging, i.e. the old minimums that used a
baseline derived from 4-level paging were technically wrong. But, KVM
always allocates roots in a separate flow, e.g. it's impossible in the
current implementation to actually need 5 new shadow pages in a single
flow. Use PT64_ROOT_MAX_LEVEL unmodified instead of subtracting 1, as
the direct usage is likely more intuitive to uninformed readers, and the
inflated minimum is unlikely to affect functionality in practice.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/kvm/mmu/mmu.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 4b4c3234d623..451e0365e5dd 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -1103,14 +1103,17 @@ static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu)
{
int r;
+ /* 1 rmap, 1 parent PTE per level, and the prefetched rmaps. */
r = mmu_topup_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache,
- 8 + PTE_PREFETCH_NUM);
+ 1 + PT64_ROOT_MAX_LEVEL + PTE_PREFETCH_NUM);
if (r)
return r;
- r = mmu_topup_memory_cache(&vcpu->arch.mmu_page_cache, 8);
+ r = mmu_topup_memory_cache(&vcpu->arch.mmu_page_cache,
+ 2 * PT64_ROOT_MAX_LEVEL);
if (r)
return r;
- return mmu_topup_memory_cache(&vcpu->arch.mmu_page_header_cache, 4);
+ return mmu_topup_memory_cache(&vcpu->arch.mmu_page_header_cache,
+ PT64_ROOT_MAX_LEVEL);
}
static void mmu_free_memory_caches(struct kvm_vcpu *vcpu)
--
2.26.0
next prev parent reply other threads:[~2020-06-05 21:43 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-05 21:38 [PATCH 00/21] KVM: Cleanup and unify kvm_mmu_memory_cache usage Sean Christopherson
2020-06-05 21:38 ` [PATCH 01/21] KVM: x86/mmu: Track the associated kmem_cache in the MMU caches Sean Christopherson
2020-06-09 21:07 ` Ben Gardon
2020-06-05 21:38 ` [PATCH 02/21] KVM: x86/mmu: Consolidate "page" variant of memory cache helpers Sean Christopherson
2020-06-09 22:54 ` Ben Gardon
2020-06-05 21:38 ` [PATCH 03/21] KVM: x86/mmu: Use consistent "mc" name for kvm_mmu_memory_cache locals Sean Christopherson
2020-06-10 22:03 ` Ben Gardon
2020-06-05 21:38 ` [PATCH 04/21] KVM: x86/mmu: Remove superfluous gotos from mmu_topup_memory_caches() Sean Christopherson
2020-06-09 22:57 ` Ben Gardon
2020-06-05 21:38 ` [PATCH 05/21] KVM: x86/mmu: Try to avoid crashing KVM if a MMU memory cache is empty Sean Christopherson
2020-06-10 22:12 ` Ben Gardon
2020-06-17 0:53 ` Sean Christopherson
2020-06-17 16:36 ` Ben Gardon
2020-06-05 21:38 ` [PATCH 06/21] KVM: x86/mmu: Move fast_page_fault() call above mmu_topup_memory_caches() Sean Christopherson
2020-06-09 23:03 ` Ben Gardon
2020-06-05 21:38 ` [PATCH 07/21] KVM: x86/mmu: Topup memory caches after walking GVA->GPA Sean Christopherson
2020-06-10 22:34 ` Ben Gardon
2020-06-05 21:38 ` Sean Christopherson [this message]
2020-06-10 22:20 ` [PATCH 08/21] KVM: x86/mmu: Clean up the gorilla math in mmu_topup_memory_caches() Ben Gardon
2020-06-05 21:38 ` [PATCH 09/21] KVM: x86/mmu: Separate the memory caches for shadow pages and gfn arrays Sean Christopherson
2020-06-09 23:56 ` Ben Gardon
2020-06-05 21:38 ` [PATCH 10/21] KVM: x86/mmu: Make __GFP_ZERO a property of the memory cache Sean Christopherson
2020-06-10 18:57 ` Ben Gardon
2020-06-22 19:40 ` Sean Christopherson
2020-06-05 21:38 ` [PATCH 11/21] KVM: x86/mmu: Zero allocate shadow pages (outside of mmu_lock) Sean Christopherson
2020-06-10 18:49 ` Ben Gardon
2020-06-05 21:38 ` [PATCH 12/21] KVM: x86/mmu: Skip filling the gfn cache for guaranteed direct MMU topups Sean Christopherson
2020-06-10 18:52 ` Ben Gardon
2020-06-05 21:38 ` [PATCH 13/21] KVM: x86/mmu: Prepend "kvm_" to memory cache helpers that will be global Sean Christopherson
2020-06-10 18:56 ` Ben Gardon
2020-06-05 21:38 ` [PATCH 14/21] KVM: Move x86's version of struct kvm_mmu_memory_cache to common code Sean Christopherson
2020-06-10 19:01 ` Ben Gardon
2020-06-10 21:58 ` Ben Gardon
2020-06-22 16:57 ` Sean Christopherson
2020-06-11 7:42 ` Marc Zyngier
2020-06-05 21:38 ` [PATCH 15/21] KVM: Move x86's MMU memory cache helpers to common KVM code Sean Christopherson
2020-06-10 20:24 ` Ben Gardon
2020-06-05 21:38 ` [PATCH 16/21] KVM: arm64: Drop @max param from mmu_topup_memory_cache() Sean Christopherson
2020-06-10 22:00 ` Ben Gardon
2020-06-11 15:59 ` Sean Christopherson
2020-06-05 21:38 ` [PATCH 17/21] KVM: arm64: Use common code's approach for __GFP_ZERO with memory caches Sean Christopherson
2020-06-11 7:59 ` Marc Zyngier
2020-06-11 15:43 ` Sean Christopherson
2020-06-11 15:51 ` Marc Zyngier
2020-06-05 21:38 ` [PATCH 18/21] KVM: arm64: Use common KVM implementation of MMU " Sean Christopherson
2020-06-11 8:01 ` Marc Zyngier
2020-06-11 15:46 ` Sean Christopherson
2020-06-05 21:38 ` [PATCH 19/21] KVM: MIPS: Drop @max param from mmu_topup_memory_cache() Sean Christopherson
2020-06-08 8:56 ` Huacai Chen
2020-06-05 21:38 ` [PATCH 20/21] KVM: MIPS: Account pages used for GPA page tables Sean Christopherson
2020-06-08 8:56 ` Huacai Chen
2020-06-05 21:38 ` [PATCH 21/21] KVM: MIPS: Use common KVM implementation of MMU memory caches Sean Christopherson
2020-06-08 8:57 ` Huacai Chen
2020-06-11 8:06 ` [PATCH 00/21] KVM: Cleanup and unify kvm_mmu_memory_cache usage Marc Zyngier
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