From nobody Fri Nov 29 23:53:57 2024 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5180616F8E7 for ; Fri, 13 Sep 2024 21:43:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726263818; cv=none; b=Z66qziPQWg0q/D6L/3gqR0UoZVeWs4q54ecGnbZa8HrnM2LoitS7hSSvE6/PRcAbK45tW9+7/dB4BKu7qbXBS8Uwm04NtHMUaSSLVMu3Q6/knO/rcq0MNbNl65JFrJptF3zIfPzQnY/XSOksKm7/R6n4WnyvfWqGFqKVCIXYobI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726263818; c=relaxed/simple; bh=091/pNCRdGXGxztyYIPeIZciZOeD1K3TPYeC5iTdipY=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Tpb1qqsi7tTkRpugDkfVVwI0hMWYFl8t+08EjTJKeJLmgKGWJYMo28aoW/2JvOsU/pR9B9I6ytXbhVEZs+1zxtS6X2XZJL28XvieYnSQKJ6GqKntN7EIKrJZDxzRYSB3dBHUzl84/MVnsoKs4JCpDthR7KAx8/4UfawNHfCYNAo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--vipinsh.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=aJuR4R2x; arc=none smtp.client-ip=209.85.128.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--vipinsh.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="aJuR4R2x" Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-69a0536b23aso59212027b3.3 for ; Fri, 13 Sep 2024 14:43:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1726263815; x=1726868615; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=rAUYJhCtl2npTL0Ze9xPEuUa5GQYdR3/oyvz0EeWkWA=; b=aJuR4R2xGap97q/ojfIWjW9d79B1nVTqY5pvfv4j/BZfvReCuuw3/OjhykXdC/8nrZ vuquw/smOuZlmFM34uMbA4xDL1mQcsZm4aJmdD3mko/r2758t98GKtRVo/2LxKBoko5G b8WihQWAt9jeZoVv+R6uEj6eocgsW7MMqIVZyjTeyfrIkbU53jOj8lv9oW4tnh6bxY1d EXlQRv+6SOyS5QqZXbgSsHcSAUF4xqzc5HaBscd/goAcd1Plp6TS0BdoIGbuRSfyxhqN kS0ak64Gp+Q4KAv+2r02TnEBhAAbA4DeELnrRozg3ah5juItW9JtBbAV19a09xJReuSk YM+A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1726263815; x=1726868615; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=rAUYJhCtl2npTL0Ze9xPEuUa5GQYdR3/oyvz0EeWkWA=; b=qFiCwkZkRsTpctcM99dZDYOPnaNgpjqH+Zy3pUq4wuNRbxJvs+mUPAzZtYICUoA52c 1leY2cGfJhPHY5fvu3uFidKBDVkpKI3wFkZqIlCyKN0FW0rGY2y/h5255hy4VBBkEQwE wu+L327z9Ge5204IhdEWnv092VaGN2+3c+D1i3VKHb3grAPdddrkOAxKaXySy9O8JYQL z/Kb3/TuDtjKJnqWRxZGS/NOqlUQ/JywNb6/56EeyjyNZzygl+pEIjKyMyK1FxwPgvXD NXhjiUrU8Bd2rO0Sez4MhtEvO2NYHCaqCD7VrvV+VDMkrDNy5LgRW5u88kIdl0X6iifj aUOQ== X-Forwarded-Encrypted: i=1; AJvYcCWuEaED7SPg9HPeOVN9yIEkLiixjmSI/XdZjvmlL7TmjZVl3z2Il0SrcBtbb1ogUyQuFs0vl+95VfoBIoM=@vger.kernel.org X-Gm-Message-State: AOJu0YzWxtzLkDzIrePpp/qPB8KDNKzeX2KblYVFac+T67tu3THHlkTq w0aDjHo9YahoZ+BTaJGzx5rL9XHlgOTHFXuuHkxcJO4U5Cd4wsWwEYasNlDt6Y8Uzs0JQHQ9eJG w7yOcpA== X-Google-Smtp-Source: AGHT+IGnKFpaMNNVc7WWMIWqQzwsj3RQhz1JMObdkTK6x2eMJDipdhA6PX0yZBLM65ZhFmOcjP+ONsH8riiy X-Received: from vipin.c.googlers.com ([35.247.89.60]) (user=vipinsh job=sendgmr) by 2002:a25:e812:0:b0:e16:51f9:59da with SMTP id 3f1490d57ef6-e1d9dc1b42emr20182276.6.1726263815170; Fri, 13 Sep 2024 14:43:35 -0700 (PDT) Date: Fri, 13 Sep 2024 14:43:16 -0700 In-Reply-To: <20240913214316.1945951-1-vipinsh@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240913214316.1945951-1-vipinsh@google.com> X-Mailer: git-send-email 2.46.0.662.g92d0881bb0-goog Message-ID: <20240913214316.1945951-3-vipinsh@google.com> Subject: [PATCH 2/2] KVM: x86/mmu: Use MMU shrinker to shrink KVM MMU memory caches From: Vipin Sharma To: seanjc@google.com, pbonzini@redhat.com Cc: dmatlack@google.com, zhi.wang.linux@gmail.com, weijiang.yang@intel.com, mizhang@google.com, liangchen.linux@gmail.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Vipin Sharma Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Use MMU shrinker to iterate through all the vCPUs of all the VMs and free pages allocated in MMU memory caches. Protect cache allocation in page fault and MMU load path from MMU shrinker by using a per vCPU mutex. In MMU shrinker, move the iterated VM to the end of the VMs list so that the pain of emptying cache spread among other VMs too. The specific caches to empty are mmu_shadow_page_cache and mmu_shadowed_info_cache as these caches store whole pages. Emptying them will give more impact to shrinker compared to other caches like mmu_pte_list_desc_cache{} and mmu_page_header_cache{} Holding per vCPU mutex lock ensures that a vCPU doesn't get surprised by finding its cache emptied after filling them up for page table allocations during page fault handling and MMU load operation. Per vCPU mutex also makes sure there is only race between MMU shrinker and all other vCPUs. This should result in very less contention. Suggested-by: Sean Christopherson Suggested-by: David Matlack Signed-off-by: Vipin Sharma --- arch/x86/include/asm/kvm_host.h | 6 +++ arch/x86/kvm/mmu/mmu.c | 69 +++++++++++++++++++++++++++------ arch/x86/kvm/mmu/paging_tmpl.h | 14 ++++--- include/linux/kvm_host.h | 1 + virt/kvm/kvm_main.c | 8 +++- 5 files changed, 81 insertions(+), 17 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_hos= t.h index cbfe31bac6cf..63eaf03111eb 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -811,6 +811,12 @@ struct kvm_vcpu_arch { */ struct kvm_mmu *walk_mmu; =20 + /* + * Protect cache from getting emptied in MMU shrinker while vCPU might + * use cache for fault handling or loading MMU. As this is a per vCPU + * lock, only contention might happen when MMU shrinker runs. + */ + struct mutex mmu_memory_cache_lock; struct kvm_mmu_memory_cache mmu_pte_list_desc_cache; struct kvm_mmu_memory_cache mmu_shadow_page_cache; struct kvm_mmu_memory_cache mmu_shadowed_info_cache; diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 213e46b55dda..8e2935347615 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -4524,29 +4524,33 @@ static int direct_page_fault(struct kvm_vcpu *vcpu,= struct kvm_page_fault *fault if (r !=3D RET_PF_INVALID) return r; =20 + mutex_lock(&vcpu->arch.mmu_memory_cache_lock); r =3D mmu_topup_memory_caches(vcpu, false); if (r) - return r; + goto out_mmu_memory_cache_unlock; =20 r =3D kvm_faultin_pfn(vcpu, fault, ACC_ALL); if (r !=3D RET_PF_CONTINUE) - return r; + goto out_mmu_memory_cache_unlock; =20 r =3D RET_PF_RETRY; write_lock(&vcpu->kvm->mmu_lock); =20 if (is_page_fault_stale(vcpu, fault)) - goto out_unlock; + goto out_mmu_unlock; =20 r =3D make_mmu_pages_available(vcpu); if (r) - goto out_unlock; + goto out_mmu_unlock; =20 r =3D direct_map(vcpu, fault); =20 -out_unlock: +out_mmu_unlock: write_unlock(&vcpu->kvm->mmu_lock); kvm_release_pfn_clean(fault->pfn); +out_mmu_memory_cache_unlock: + mutex_unlock(&vcpu->arch.mmu_memory_cache_lock); + return r; } =20 @@ -4617,25 +4621,28 @@ static int kvm_tdp_mmu_page_fault(struct kvm_vcpu *= vcpu, if (r !=3D RET_PF_INVALID) return r; =20 + mutex_lock(&vcpu->arch.mmu_memory_cache_lock); r =3D mmu_topup_memory_caches(vcpu, false); if (r) - return r; + goto out_mmu_memory_cache_unlock; =20 r =3D kvm_faultin_pfn(vcpu, fault, ACC_ALL); if (r !=3D RET_PF_CONTINUE) - return r; + goto out_mmu_memory_cache_unlock; =20 r =3D RET_PF_RETRY; read_lock(&vcpu->kvm->mmu_lock); =20 if (is_page_fault_stale(vcpu, fault)) - goto out_unlock; + goto out_mmu_unlock; =20 r =3D kvm_tdp_mmu_map(vcpu, fault); =20 -out_unlock: +out_mmu_unlock: read_unlock(&vcpu->kvm->mmu_lock); kvm_release_pfn_clean(fault->pfn); +out_mmu_memory_cache_unlock: + mutex_unlock(&vcpu->arch.mmu_memory_cache_lock); return r; } #endif @@ -5691,6 +5698,7 @@ int kvm_mmu_load(struct kvm_vcpu *vcpu) { int r; =20 + mutex_lock(&vcpu->arch.mmu_memory_cache_lock); r =3D mmu_topup_memory_caches(vcpu, !vcpu->arch.mmu->root_role.direct); if (r) goto out; @@ -5717,6 +5725,7 @@ int kvm_mmu_load(struct kvm_vcpu *vcpu) */ kvm_x86_call(flush_tlb_current)(vcpu); out: + mutex_unlock(&vcpu->arch.mmu_memory_cache_lock); return r; } =20 @@ -6303,6 +6312,7 @@ int kvm_mmu_create(struct kvm_vcpu *vcpu) if (!vcpu->arch.mmu_shadow_page_cache.init_value) vcpu->arch.mmu_shadow_page_cache.gfp_zero =3D __GFP_ZERO; =20 + mutex_init(&vcpu->arch.mmu_memory_cache_lock); vcpu->arch.mmu =3D &vcpu->arch.root_mmu; vcpu->arch.walk_mmu =3D &vcpu->arch.root_mmu; =20 @@ -6997,13 +7007,50 @@ void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm,= u64 gen) static unsigned long mmu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc) { - return SHRINK_STOP; + struct kvm *kvm, *next_kvm, *first_kvm =3D NULL; + unsigned long i, freed =3D 0; + struct kvm_vcpu *vcpu; + + mutex_lock(&kvm_lock); + list_for_each_entry_safe(kvm, next_kvm, &vm_list, vm_list) { + if (!first_kvm) + first_kvm =3D kvm; + else if (first_kvm =3D=3D kvm) + break; + + list_move_tail(&kvm->vm_list, &vm_list); + + kvm_for_each_vcpu(i, vcpu, kvm) { + if (!mutex_trylock(&vcpu->arch.mmu_memory_cache_lock)) + continue; + freed +=3D kvm_mmu_empty_memory_cache(&vcpu->arch.mmu_shadow_page_cache= ); + freed +=3D kvm_mmu_empty_memory_cache(&vcpu->arch.mmu_shadowed_info_cac= he); + mutex_unlock(&vcpu->arch.mmu_memory_cache_lock); + if (freed >=3D sc->nr_to_scan) + goto out; + } + } +out: + mutex_unlock(&kvm_lock); + return freed; } =20 static unsigned long mmu_shrink_count(struct shrinker *shrink, struct shrink_control *sc) { - return SHRINK_EMPTY; + unsigned long i, count =3D 0; + struct kvm_vcpu *vcpu; + struct kvm *kvm; + + mutex_lock(&kvm_lock); + list_for_each_entry(kvm, &vm_list, vm_list) { + kvm_for_each_vcpu(i, vcpu, kvm) { + count +=3D READ_ONCE(vcpu->arch.mmu_shadow_page_cache.nobjs); + count +=3D READ_ONCE(vcpu->arch.mmu_shadowed_info_cache.nobjs); + } + } + mutex_unlock(&kvm_lock); + return !count ? SHRINK_EMPTY : count; } =20 static struct shrinker *mmu_shrinker; diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h index 405bd7ceee2a..084a5c532078 100644 --- a/arch/x86/kvm/mmu/paging_tmpl.h +++ b/arch/x86/kvm/mmu/paging_tmpl.h @@ -809,13 +809,14 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, s= truct kvm_page_fault *fault return RET_PF_EMULATE; } =20 + mutex_lock(&vcpu->arch.mmu_memory_cache_lock); r =3D mmu_topup_memory_caches(vcpu, true); if (r) - return r; + goto out_mmu_memory_cache_unlock; =20 r =3D kvm_faultin_pfn(vcpu, fault, walker.pte_access); if (r !=3D RET_PF_CONTINUE) - return r; + goto out_mmu_memory_cache_unlock; =20 /* * Do not change pte_access if the pfn is a mmio page, otherwise @@ -840,16 +841,19 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, s= truct kvm_page_fault *fault write_lock(&vcpu->kvm->mmu_lock); =20 if (is_page_fault_stale(vcpu, fault)) - goto out_unlock; + goto out_mmu_unlock; =20 r =3D make_mmu_pages_available(vcpu); if (r) - goto out_unlock; + goto out_mmu_unlock; r =3D FNAME(fetch)(vcpu, fault, &walker); =20 -out_unlock: +out_mmu_unlock: write_unlock(&vcpu->kvm->mmu_lock); kvm_release_pfn_clean(fault->pfn); +out_mmu_memory_cache_unlock: + mutex_unlock(&vcpu->arch.mmu_memory_cache_lock); + return r; } =20 diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index b23c6d48392f..288e503f14a0 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -1446,6 +1446,7 @@ void kvm_flush_remote_tlbs_memslot(struct kvm *kvm, int kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int min); int __kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int capa= city, int min); int kvm_mmu_memory_cache_nr_free_objects(struct kvm_mmu_memory_cache *mc); +int kvm_mmu_empty_memory_cache(struct kvm_mmu_memory_cache *mc); void kvm_mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc); void *kvm_mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc); #endif diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index cb2b78e92910..5d89ca218791 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -451,15 +451,21 @@ int kvm_mmu_memory_cache_nr_free_objects(struct kvm_m= mu_memory_cache *mc) return mc->nobjs; } =20 -void kvm_mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc) +int kvm_mmu_empty_memory_cache(struct kvm_mmu_memory_cache *mc) { + int freed =3D mc->nobjs; while (mc->nobjs) { if (mc->kmem_cache) kmem_cache_free(mc->kmem_cache, mc->objects[--mc->nobjs]); else free_page((unsigned long)mc->objects[--mc->nobjs]); } + return freed; +} =20 +void kvm_mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc) +{ + kvm_mmu_empty_memory_cache(mc); kvfree(mc->objects); =20 mc->objects =3D NULL; --=20 2.46.0.662.g92d0881bb0-goog