From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.55.52.93]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 581AF20B1C for ; Fri, 13 Oct 2023 16:22:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="VukHdDA8" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1697214141; x=1728750141; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=8HZ1k3AcAih4bSHLM8xODeQ0GJIR0iLWB3qxJlRJllM=; b=VukHdDA8gkSHlUyex6ih6FP81pLC+Q/OP7XxkUf/C4+En7DwLVLrlTVR Th+UYUocpzFT8EJFQhxG7m7ldCDIYN+6x2qgQjyTdXx3rUjiZmBeb+2XP s5TAiZBmlbJTgZ2XeqhMo9GObLz9XZxdyymEbIcUskmwYqPGDRUwiDFxD CeXpA03jE8DxUvRnjuV8W9s7q1mwN70bDDr/0fZtBWzA2C/AanndBMUap TAcGZUg+al1wapvsjtCpZI5RrBdwwpHLu5IvKDfuqru164/uCuinCsF/3 z88VeXIqns2Wh9iVLyTB1IAEgaReJ5T9WqbBbSB/lthNHGBdJr8Tzb+EF w==; X-IronPort-AV: E=McAfee;i="6600,9927,10862"; a="382440265" X-IronPort-AV: E=Sophos;i="6.03,222,1694761200"; d="scan'208";a="382440265" Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Oct 2023 09:22:20 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10862"; a="1002002017" X-IronPort-AV: E=Sophos;i="6.03,222,1694761200"; d="scan'208";a="1002002017" Received: from bgras-mobl1.ger.corp.intel.com (HELO box.shutemov.name) ([10.252.59.145]) by fmsmga006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Oct 2023 09:22:12 -0700 Received: by box.shutemov.name (Postfix, from userid 1000) id 2F9D3104A05; Fri, 13 Oct 2023 19:22:10 +0300 (+03) Date: Fri, 13 Oct 2023 19:22:10 +0300 From: "Kirill A. Shutemov" To: Michael Roth Cc: Borislav Petkov , Andy Lutomirski , Dave Hansen , Sean Christopherson , Andrew Morton , Joerg Roedel , Ard Biesheuvel , Andi Kleen , Kuppuswamy Sathyanarayanan , David Rientjes , Vlastimil Babka , Tom Lendacky , Thomas Gleixner , Peter Zijlstra , Paolo Bonzini , Ingo Molnar , Dario Faggioli , Mike Rapoport , David Hildenbrand , Mel Gorman , marcelo.cerri@canonical.com, tim.gardner@canonical.com, khalid.elmously@canonical.com, philip.cox@canonical.com, aarcange@redhat.com, peterx@redhat.com, x86@kernel.org, linux-mm@kvack.org, linux-coco@lists.linux.dev, linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCHv14 5/9] efi: Add unaccepted memory support Message-ID: <20231013162210.bqepgz6wnh7uohqq@box> References: <20230606142637.5171-1-kirill.shutemov@linux.intel.com> <20230606142637.5171-6-kirill.shutemov@linux.intel.com> <20231010210518.jguawj7bscwgvszv@amd.com> <20231013123358.y4pcdp5fgtt4ax6g@box.shutemov.name> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231013123358.y4pcdp5fgtt4ax6g@box.shutemov.name> On Fri, Oct 13, 2023 at 03:33:58PM +0300, Kirill A. Shutemov wrote: > > While testing SNP guests running today's tip/master (ef19bc9dddc3) I ran > > into what seems to be fairly significant lock contention due to the > > unaccepted_memory_lock spinlock above, which results in a constant stream > > of soft-lockups until the workload gets all its memory accepted/faulted > > in if the guest has around 16+ vCPUs. > > > > I've included the guest dmesg traces I was seeing below. > > > > In this case I was running a 32 vCPU guest with 200GB of memory running on > > a 256 thread EPYC (Milan) system, and can trigger the above situation fairly > > reliably by running the following workload in a freshly-booted guests: > > > > stress --vm 32 --vm-bytes 5G --vm-keep > > > > Scaling up the number of stress threads and vCPUs should make it easier > > to reproduce. > > > > Other than unresponsiveness/lockup messages until the memory is accepted, > > the guest seems to continue running fine, but for large guests where > > unaccepted memory is more likely to be useful, it seems like it could be > > an issue, especially when consider 100+ vCPU guests. > > Okay, sorry for delay. It took time to reproduce it with TDX. > > I will look what can be done. Could you check if the patch below helps? diff --git a/drivers/firmware/efi/unaccepted_memory.c b/drivers/firmware/efi/unaccepted_memory.c index 853f7dc3c21d..591da3f368fa 100644 --- a/drivers/firmware/efi/unaccepted_memory.c +++ b/drivers/firmware/efi/unaccepted_memory.c @@ -8,6 +8,14 @@ /* Protects unaccepted memory bitmap */ static DEFINE_SPINLOCK(unaccepted_memory_lock); +struct accept_range { + struct list_head list; + unsigned long start; + unsigned long end; +}; + +static LIST_HEAD(accepting_list); + /* * accept_memory() -- Consult bitmap and accept the memory if needed. * @@ -24,6 +32,7 @@ void accept_memory(phys_addr_t start, phys_addr_t end) { struct efi_unaccepted_memory *unaccepted; unsigned long range_start, range_end; + struct accept_range range, *entry; unsigned long flags; u64 unit_size; @@ -80,7 +89,25 @@ void accept_memory(phys_addr_t start, phys_addr_t end) range_start = start / unit_size; + range.start = start; + range.end = end; +retry: spin_lock_irqsave(&unaccepted_memory_lock, flags); + + list_for_each_entry(entry, &accepting_list, list) { + if (entry->end < start) + continue; + if (entry->start > end) + continue; + spin_unlock_irqrestore(&unaccepted_memory_lock, flags); + + /* Somebody else accepting the range */ + cpu_relax(); + goto retry; + } + + list_add(&range.list, &accepting_list); + for_each_set_bitrange_from(range_start, range_end, unaccepted->bitmap, DIV_ROUND_UP(end, unit_size)) { unsigned long phys_start, phys_end; @@ -89,9 +116,15 @@ void accept_memory(phys_addr_t start, phys_addr_t end) phys_start = range_start * unit_size + unaccepted->phys_base; phys_end = range_end * unit_size + unaccepted->phys_base; + spin_unlock_irqrestore(&unaccepted_memory_lock, flags); + arch_accept_memory(phys_start, phys_end); + + spin_lock_irqsave(&unaccepted_memory_lock, flags); bitmap_clear(unaccepted->bitmap, range_start, len); } + + list_del(&range.list); spin_unlock_irqrestore(&unaccepted_memory_lock, flags); } -- Kiryl Shutsemau / Kirill A. Shutemov