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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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231013123358.y4pcdp5fgtt4ax6g@box.shutemov.name> X-Stat-Signature: frny74x4uah7n4ydxop7zihfg9qfiigc X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: A95B3140038 X-Rspam-User: X-HE-Tag: 1697214142-578381 X-HE-Meta: U2FsdGVkX1/S4pO0AqRcqF/Kjdn1Egx7eXnfF/NdEe2eGAd583KINhaHCuB7y4vuhgWAAv5iMMj/8g4t8D7b601HT22REAo0GHr5Wfhf6I56PwIWJARB9QGVyVzkJg8ZmmQEa+XV78Y1zB+xhO+kWCDZj6K7G2qpkSoxufEqPk0Cb7IEXZ3DMSKvd39jJ2gQ3suitQIUtmoG0GTLJGfNn51tOOBel6B0b56wN6U2FsAWQGU5lqZMPL1jGsDtsKlqqmEq8k3oS62+tFZhy6DsPu/xqujW6UkzW8haNbr1PywDikOIJ13MTghg+vskSJPFJZpjLiF4nDBHhodHUYFmNYw+XXcjoeG+guwRnaW10oMt/QeLhbbO6wwM6c4TmXPFjncrfiaeyGdCUpJbW+g9pH+uxH4kmrRxxlEi2zg8HkUhpx0Sm95nPqkEtlqS36LUvCr28UdIEIfH7Yh6fHH1NkS8N5hjNspUSrtpzmbTgpWxsPBUWRaLUpHxo1Bxs35xqT4uNyOWxbo6/UU28C30weu56YL1/oByi3u7FnbkGbQH94TdgEd06ZTcLuMBm3iMVqg4AXJpiI9CpqrVjkKrWhyj8ayYUPBkiiYU/pZ5hoC2756S3jXrXYi17QdDOI4RLrpvZJI8PVVLqGzuf26G9DnRTSv3YxLoKlaT7UQG7StMMztupWJP/iqGftqKuf9a+I1QFvTxp8Z9BoCJBKrIyHGeAcCdTDVxdym4uMNw/n4poDLlfTqeWORS9JKBXWG2YBEi88j1R32fadtMk2Mj3FL8NMU3wp5nVsFQuVHM24j8xRzRy/WfUj57FQYKLrghBvwKvFUcy2mbQ81D3usEqL9Uw4W4ydNTha8dFo80UhyrnQK6wyANf9bgiduRCWpfuGSQtqQbPWsJ/8pOSeWG9HUw1fK8wqOeetDUt/WTRFHV/2NLGKe8xh8jKuTlaszIEu78Cj2bm06fJLO4/JE 4Dibve9v 5mWxsg1YSUINGrrQPgwhrmgK5Zf5VyZ4l0G5O169ZhC9oie6btvm5n15w5Lc7R3kKsJrZr1xz7Uyo89azTFtriv+MtFg/9JHJ/wEfLOCRn79+oMMWQo0wjQSvum+2u8HL6Jt+ X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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