From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 1E1A4302CB3; Fri, 28 Nov 2025 09:32:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764322380; cv=none; b=fE712UsgaZTr1oOsoxlx+H4B7oGGVwHH9AfuCDQpNwF+vn6wFndJXb5UFfwQHr8XJWYZG8ezQa3q4rmNeQ6LKpEP/ILZ9VWWFHFNnSrk9XVQ97cLiEspmelF3n7fqIq7kwn/lRqGFwfKUH0dtJWZd170Wk1ZFcnFqJUFlUho7/o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764322380; c=relaxed/simple; bh=ax3ZOoXlAAXf0E1NKzt1mIJarEydCCkiax1Sg5VyIqw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=d797hl7bXzCtBK6rX1oHYSrtrt65p8WSOVynV6BJxSn8P5oPaVnbcv/D+xaE8BAF/GugIL/o/jgNP9Xy7O0+pkt79URWFI5hJrEurGZ5KZGXOJUnwbUNXqK3lVN9YrF2vmnP8s5LvGdif2ouSkWJKpZUQNM/xBPOxAm7XZg74cM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dNM/q7O+; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="dNM/q7O+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A3220C2BCB3; Fri, 28 Nov 2025 09:32:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764322379; bh=ax3ZOoXlAAXf0E1NKzt1mIJarEydCCkiax1Sg5VyIqw=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=dNM/q7O+Q/6NnEzCCUed7ld+KJdoKuokwlWfnkkD/a71Rft62arVXl4eCr1vBlU1F WmfuBjD3c68G/GyQkXJqEq1L2sddXqE2tJRpZFDWwC2vs/A/8kY6AhAzsw5/FLrkyV R4VcXTepa2qlFffv/FxJo5h+nbpbv2PhizYFygfVBEFX6lJVMIpmCSXvKdP6XxbV2r 23Z914SEMznasS6bYwwWVEA96zf4yMsYlWsvkUqtLhSJ5TxgPFqfrz8+MNEUcgjzBY qSQxClNL3389d0tOtHBMrqO0dbZbmuyw0r9nBcV2T6aRXCH6PreZxJtltd1llwxusk nxvIjMXVVvEPQ== Message-ID: Date: Fri, 28 Nov 2025 10:32:53 +0100 Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 2/4] mm: Add support for unaccepted memory hotplug To: "Pratik R. Sampat" , linux-mm@kvack.org, linux-coco@lists.linux.dev, linux-efi@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, kas@kernel.org, ardb@kernel.org, akpm@linux-foundation.org, osalvador@suse.de, thomas.lendacky@amd.com, michael.roth@amd.com References: <20251125175753.1428857-1-prsampat@amd.com> <20251125175753.1428857-3-prsampat@amd.com> From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: <20251125175753.1428857-3-prsampat@amd.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 11/25/25 18:57, Pratik R. Sampat wrote: > The unaccepted memory structure currently only supports accepting memory > present at boot time. The unaccepted table uses a fixed-size bitmap > reserved in memblock based on the initial memory layout, preventing > dynamic addition of memory ranges after boot. This causes guest > termination when memory is hot-added in a secure virtual machine due to > accessing pages that have not transitioned to private before use. > > Extend the unaccepted memory framework to handle hotplugged memory by > dynamically managing the unaccepted bitmap. Allocate a new bitmap when > hotplugged ranges exceed the reserved bitmap capacity and switch to > kernel-managed allocation. > > Hotplugged memory also follows the same acceptance policy using the > accept_memory=[eager|lazy] kernel parameter to accept memory either > up-front when added or before first use. > > Signed-off-by: Pratik R. Sampat > --- > arch/x86/boot/compressed/efi.h | 1 + > .../firmware/efi/libstub/unaccepted_memory.c | 1 + > drivers/firmware/efi/unaccepted_memory.c | 83 +++++++++++++++++++ > include/linux/efi.h | 1 + > include/linux/mm.h | 11 +++ > mm/memory_hotplug.c | 7 ++ > mm/page_alloc.c | 2 + > 7 files changed, 106 insertions(+) > > diff --git a/arch/x86/boot/compressed/efi.h b/arch/x86/boot/compressed/efi.h > index 4f7027f33def..a220a1966cae 100644 > --- a/arch/x86/boot/compressed/efi.h > +++ b/arch/x86/boot/compressed/efi.h > @@ -102,6 +102,7 @@ struct efi_unaccepted_memory { > u32 unit_size; > u64 phys_base; > u64 size; > + bool mem_reserved; > unsigned long *bitmap; > }; > > diff --git a/drivers/firmware/efi/libstub/unaccepted_memory.c b/drivers/firmware/efi/libstub/unaccepted_memory.c > index c1370fc14555..b16bd61c12bf 100644 > --- a/drivers/firmware/efi/libstub/unaccepted_memory.c > +++ b/drivers/firmware/efi/libstub/unaccepted_memory.c > @@ -83,6 +83,7 @@ efi_status_t allocate_unaccepted_bitmap(__u32 nr_desc, > unaccepted_table->unit_size = EFI_UNACCEPTED_UNIT_SIZE; > unaccepted_table->phys_base = unaccepted_start; > unaccepted_table->size = bitmap_size; > + unaccepted_table->mem_reserved = true; > memset(unaccepted_table->bitmap, 0, bitmap_size); > > status = efi_bs_call(install_configuration_table, > diff --git a/drivers/firmware/efi/unaccepted_memory.c b/drivers/firmware/efi/unaccepted_memory.c > index 4479aad258f8..8537812346e2 100644 > --- a/drivers/firmware/efi/unaccepted_memory.c > +++ b/drivers/firmware/efi/unaccepted_memory.c > @@ -218,6 +218,89 @@ bool range_contains_unaccepted_memory(phys_addr_t start, unsigned long size) > return ret; > } > > +static int extend_unaccepted_bitmap(phys_addr_t mem_range_start, > + unsigned long mem_range_size) > +{ > + struct efi_unaccepted_memory *unacc_tbl; > + unsigned long *old_bitmap, *new_bitmap; > + phys_addr_t start, end, mem_range_end; > + u64 phys_base, size, unit_size; > + unsigned long flags; > + > + unacc_tbl = efi_get_unaccepted_table(); > + if (!unacc_tbl || !unacc_tbl->unit_size) > + return -EIO; > + > + unit_size = unacc_tbl->unit_size; > + phys_base = unacc_tbl->phys_base; > + > + mem_range_end = round_up(mem_range_start + mem_range_size, unit_size); > + size = DIV_ROUND_UP(mem_range_end - phys_base, unit_size * BITS_PER_BYTE); > + > + /* Translate to offsets from the beginning of the bitmap */ > + start = mem_range_start - phys_base; > + end = mem_range_end - phys_base; > + > + old_bitmap = efi_get_unaccepted_bitmap(); > + if (!old_bitmap) > + return -EIO; > + > + /* If the bitmap is already large enough, just set the bits */ > + if (unacc_tbl->size >= size) { > + spin_lock_irqsave(&unaccepted_memory_lock, flags); > + bitmap_set(old_bitmap, start / unit_size, (end - start) / unit_size); > + spin_unlock_irqrestore(&unaccepted_memory_lock, flags); > + > + return 0; > + } > + > + /* Reserved memblocks cannot be extended so allocate a new bitmap */ > + if (unacc_tbl->mem_reserved) { > + new_bitmap = kzalloc(size, GFP_KERNEL); > + if (!new_bitmap) > + return -ENOMEM; > + > + spin_lock_irqsave(&unaccepted_memory_lock, flags); > + memcpy(new_bitmap, old_bitmap, unacc_tbl->size); > + unacc_tbl->mem_reserved = false; > + free_reserved_area(old_bitmap, old_bitmap + unacc_tbl->size, -1, NULL); > + spin_unlock_irqrestore(&unaccepted_memory_lock, flags); > + } else { > + new_bitmap = krealloc(old_bitmap, size, GFP_KERNEL); > + if (!new_bitmap) > + return -ENOMEM; > + > + /* Zero the bitmap from the range it was extended from */ > + memset(new_bitmap + unacc_tbl->size, 0, size - unacc_tbl->size); > + } > + > + bitmap_set(new_bitmap, start / unit_size, (end - start) / unit_size); > + > + spin_lock_irqsave(&unaccepted_memory_lock, flags); > + unacc_tbl->size = size; > + unacc_tbl->bitmap = (unsigned long *)__pa(new_bitmap); > + spin_unlock_irqrestore(&unaccepted_memory_lock, flags); > + > + return 0; > +} > + > +int accept_hotplug_memory(phys_addr_t mem_range_start, unsigned long mem_range_size) > +{ > + int ret; > + > + if (!IS_ENABLED(CONFIG_UNACCEPTED_MEMORY)) > + return 0; > + > + ret = extend_unaccepted_bitmap(mem_range_start, mem_range_size); > + if (ret) > + return ret; > + > + if (!mm_lazy_accept_enabled()) > + accept_memory(mem_range_start, mem_range_size); > + > + return 0; > +} > + > #ifdef CONFIG_PROC_VMCORE > static bool unaccepted_memory_vmcore_pfn_is_ram(struct vmcore_cb *cb, > unsigned long pfn) > diff --git a/include/linux/efi.h b/include/linux/efi.h > index a74b393c54d8..1021eb78388f 100644 > --- a/include/linux/efi.h > +++ b/include/linux/efi.h > @@ -545,6 +545,7 @@ struct efi_unaccepted_memory { > u32 unit_size; > u64 phys_base; > u64 size; > + bool mem_reserved; > unsigned long *bitmap; > }; > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 1ae97a0b8ec7..bb43876e6c47 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -4077,6 +4077,9 @@ int set_anon_vma_name(unsigned long addr, unsigned long size, > > bool range_contains_unaccepted_memory(phys_addr_t start, unsigned long size); > void accept_memory(phys_addr_t start, unsigned long size); > +int accept_hotplug_memory(phys_addr_t mem_range_start, > + unsigned long mem_range_size); > +bool mm_lazy_accept_enabled(void); > > #else > > @@ -4090,6 +4093,14 @@ static inline void accept_memory(phys_addr_t start, unsigned long size) > { > } > > +static inline int accept_hotplug_memory(phys_addr_t mem_range_start, > + unsigned long mem_range_size) > +{ > + return 0; > +} > + > +static inline bool mm_lazy_accept_enabled(void) { return false; } > + > #endif > > static inline bool pfn_is_unaccepted_memory(unsigned long pfn) > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 74318c787715..bf8086682b66 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1581,6 +1581,13 @@ int add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) > if (!strcmp(res->name, "System RAM")) > firmware_map_add_hotplug(start, start + size, "System RAM"); > > + ret = accept_hotplug_memory(start, size); What makes this special that we have to have "hotplug_memory" as part of the name? Staring at the helper itself, there isn't anything really hotplug specific happening in there except extending the bitmap, maybe? -- Cheers David