From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oliver Upton Subject: Re: [PATCH v5 4/4] KVM: arm64/mmu: count KVM s2 mmu usage in secondary pagetable stats Date: Tue, 28 Jun 2022 18:53:55 +0000 Message-ID: References: <20220606222058.86688-1-yosryahmed@google.com> <20220606222058.86688-5-yosryahmed@google.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1656442441; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=htPFhHOsa3d7/VGnFqnbz5VFkkx8xDdtzMvjjntEVQQ=; b=d6djTxUwEkHGAYEqJ+FSn4G/FZeJSZoQaoOZxxQhJaqcI2qvYIgXT+trdlZ0GWC661TwyO 1oiSHS8oHUyMAMhElHKJhcjJFylgZXvccpHWWmhbSO2Tv35HgJpLHoM6RfUaZ/baIXg/yK KB8JzslXVDM8K4q77AikRR+g7gpG87A= Content-Disposition: inline In-Reply-To: <20220606222058.86688-5-yosryahmed-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Yosry Ahmed Cc: Tejun Heo , Johannes Weiner , Zefan Li , Marc Zyngier , James Morse , Alexandru Elisei , Suzuki K Poulose , Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Andrew Morton , Michal Hocko , Roman Gushchin , Shakeel Butt , kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kvmarm-FPEHb7Xf0XXUo1n7N8X6UoWGPAHP3yOg@public.gmane.org Hi Yosry, On Mon, Jun 06, 2022 at 10:20:58PM +0000, Yosry Ahmed wrote: > Count the pages used by KVM in arm64 for stage2 mmu in secondary pagetable > stats. You could probably benefit from being a bit more verbose in the commit message here as well, per Sean's feedback. > Signed-off-by: Yosry Ahmed > --- > arch/arm64/kvm/mmu.c | 36 ++++++++++++++++++++++++++++++++---- > 1 file changed, 32 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > index f5651a05b6a85..80bc92601fd96 100644 > --- a/arch/arm64/kvm/mmu.c > +++ b/arch/arm64/kvm/mmu.c > @@ -92,9 +92,13 @@ static bool kvm_is_device_pfn(unsigned long pfn) > static void *stage2_memcache_zalloc_page(void *arg) > { > struct kvm_mmu_memory_cache *mc = arg; > + void *virt; > > /* Allocated with __GFP_ZERO, so no need to zero */ > - return kvm_mmu_memory_cache_alloc(mc); > + virt = kvm_mmu_memory_cache_alloc(mc); > + if (virt) > + kvm_account_pgtable_pages(virt, 1); > + return virt; > } > > static void *kvm_host_zalloc_pages_exact(size_t size) > @@ -102,6 +106,21 @@ static void *kvm_host_zalloc_pages_exact(size_t size) > return alloc_pages_exact(size, GFP_KERNEL_ACCOUNT | __GFP_ZERO); > } > > +static void *kvm_s2_zalloc_pages_exact(size_t size) > +{ > + void *virt = kvm_host_zalloc_pages_exact(size); > + > + if (virt) > + kvm_account_pgtable_pages(virt, (size >> PAGE_SHIFT)); > + return virt; > +} > + > +static void kvm_s2_free_pages_exact(void *virt, size_t size) > +{ > + kvm_account_pgtable_pages(virt, -(size >> PAGE_SHIFT)); > + free_pages_exact(virt, size); > +} > + > static void kvm_host_get_page(void *addr) > { > get_page(virt_to_page(addr)); > @@ -112,6 +131,15 @@ static void kvm_host_put_page(void *addr) > put_page(virt_to_page(addr)); > } > > +static void kvm_s2_put_page(void *addr) > +{ > + struct page *p = virt_to_page(addr); > + /* Dropping last refcount, the page will be freed */ > + if (page_count(p) == 1) > + kvm_account_pgtable_pages(addr, -1); > + put_page(p); Probably more of a note to myself with the parallel fault series, but this is a race waiting to happen. This only works because stage 2 pages are dropped behind the write lock. Besides the commit message nit: Reviewed-by: Oliver Upton