From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 93D6714A4E2 for ; Wed, 16 Oct 2024 14:46:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729090020; cv=none; b=mmk3aANnZOoNnCSbaSK1UcmqqRszn+/KUockR466scDhpfcGKOf6s2eB671qEm5ZeHjIhUBdD2aJsBemjXgpmu1umgrlKGSFVC7rVZoqapQspT51PfF3lllH2T6+bIoaJaydxFWncemvDkefqX5hqrlHbS8pY0MoqU0M2YEbyHA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729090020; c=relaxed/simple; bh=k1qcvyiAgG0wcax6nxyGKvW8bqyfC1GOW9wkLRQqBcM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ezmozjTJG0Efb1jw2QU3lGpI6M9h1U6LAbAkZN5zKyCuuplm+O0uRBzumiYCCq0Vc/kDPg0rJxv/2CKIbBFOero+wPV0UhCDaEpehyxsIn/p40DdIGebrge6jp7i/4u4ptkevuZvX6GnR5ZqVnZ1fcUqKiTJ7z4x+M7tTTxek4w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 8CE951007; Wed, 16 Oct 2024 07:47:27 -0700 (PDT) Received: from [10.1.28.177] (XHFQ2J9959.cambridge.arm.com [10.1.28.177]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 47B933F71E; Wed, 16 Oct 2024 07:46:55 -0700 (PDT) Message-ID: <829b5662-13c0-4728-894c-b2d578681b11@arm.com> Date: Wed, 16 Oct 2024 15:46:53 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v1 36/57] xen: Remove PAGE_SIZE compile-time constant assumption Content-Language: en-GB To: Andrew Morton , Anshuman Khandual , Ard Biesheuvel , Catalin Marinas , David Hildenbrand , Greg Marsden , Ivan Ivanov , Kalesh Singh , Marc Zyngier , Mark Rutland , Matthias Brugger , Miroslav Benes , Will Deacon , Juergen Gross , Stefano Stabellini Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, xen-devel@lists.xenproject.org References: <20241014105514.3206191-1-ryan.roberts@arm.com> <20241014105912.3207374-1-ryan.roberts@arm.com> <20241014105912.3207374-36-ryan.roberts@arm.com> From: Ryan Roberts In-Reply-To: <20241014105912.3207374-36-ryan.roberts@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit + Juergen Gross, Stefano Stabellini This was a rather tricky series to get the recipients correct for and my script did not realize that "supporter" was a pseudonym for "maintainer" so you were missed off the original post. Appologies! More context in cover letter: https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@arm.com/ On 14/10/2024 11:58, Ryan Roberts wrote: > To prepare for supporting boot-time page size selection, refactor code > to remove assumptions about PAGE_SIZE being compile-time constant. Code > intended to be equivalent when compile-time page size is active. > > Allocate enough "frame_list" static storage in the balloon driver for > the maximum supported page size. Although continue to use only the first > PAGE_SIZE of the buffer at run-time to maintain existing behaviour. > > Refactor xen_biovec_phys_mergeable() to convert ifdeffery to c if/else. > For compile-time page size, the compiler will choose one branch and > strip the dead one. For boot-time, it can be evaluated at run time. > > Refactor a BUILD_BUG_ON to evaluate the limit (when the minimum > supported page size is selected at boot-time). > > Reserve enough storage for max page size in "struct remap_data" and > "struct xenbus_map_node". > > Signed-off-by: Ryan Roberts > --- > > ***NOTE*** > Any confused maintainers may want to read the cover note here for context: > https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@arm.com/ > > drivers/xen/balloon.c | 11 ++++++----- > drivers/xen/biomerge.c | 12 ++++++------ > drivers/xen/privcmd.c | 2 +- > drivers/xen/xenbus/xenbus_client.c | 5 +++-- > drivers/xen/xlate_mmu.c | 6 +++--- > include/xen/page.h | 2 ++ > 6 files changed, 21 insertions(+), 17 deletions(-) > > diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c > index 528395133b4f8..0ed5f6453af0e 100644 > --- a/drivers/xen/balloon.c > +++ b/drivers/xen/balloon.c > @@ -131,7 +131,8 @@ struct balloon_stats balloon_stats; > EXPORT_SYMBOL_GPL(balloon_stats); > > /* We increase/decrease in batches which fit in a page */ > -static xen_pfn_t frame_list[PAGE_SIZE / sizeof(xen_pfn_t)]; > +static xen_pfn_t frame_list[PAGE_SIZE_MAX / sizeof(xen_pfn_t)]; > +#define FRAME_LIST_NR_ENTRIES (PAGE_SIZE / sizeof(xen_pfn_t)) > > > /* List of ballooned pages, threaded through the mem_map array. */ > @@ -389,8 +390,8 @@ static enum bp_state increase_reservation(unsigned long nr_pages) > unsigned long i; > struct page *page; > > - if (nr_pages > ARRAY_SIZE(frame_list)) > - nr_pages = ARRAY_SIZE(frame_list); > + if (nr_pages > FRAME_LIST_NR_ENTRIES) > + nr_pages = FRAME_LIST_NR_ENTRIES; > > page = list_first_entry_or_null(&ballooned_pages, struct page, lru); > for (i = 0; i < nr_pages; i++) { > @@ -434,8 +435,8 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp) > int ret; > LIST_HEAD(pages); > > - if (nr_pages > ARRAY_SIZE(frame_list)) > - nr_pages = ARRAY_SIZE(frame_list); > + if (nr_pages > FRAME_LIST_NR_ENTRIES) > + nr_pages = FRAME_LIST_NR_ENTRIES; > > for (i = 0; i < nr_pages; i++) { > page = alloc_page(gfp); > diff --git a/drivers/xen/biomerge.c b/drivers/xen/biomerge.c > index 05a286d24f148..28f0887e40026 100644 > --- a/drivers/xen/biomerge.c > +++ b/drivers/xen/biomerge.c > @@ -8,16 +8,16 @@ > bool xen_biovec_phys_mergeable(const struct bio_vec *vec1, > const struct page *page) > { > -#if XEN_PAGE_SIZE == PAGE_SIZE > - unsigned long bfn1 = pfn_to_bfn(page_to_pfn(vec1->bv_page)); > - unsigned long bfn2 = pfn_to_bfn(page_to_pfn(page)); > + if (XEN_PAGE_SIZE == PAGE_SIZE) { > + unsigned long bfn1 = pfn_to_bfn(page_to_pfn(vec1->bv_page)); > + unsigned long bfn2 = pfn_to_bfn(page_to_pfn(page)); > + > + return bfn1 + PFN_DOWN(vec1->bv_offset + vec1->bv_len) == bfn2; > + } > > - return bfn1 + PFN_DOWN(vec1->bv_offset + vec1->bv_len) == bfn2; > -#else > /* > * XXX: Add support for merging bio_vec when using different page > * size in Xen and Linux. > */ > return false; > -#endif > } > diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c > index 9563650dfbafc..847f7b806caf7 100644 > --- a/drivers/xen/privcmd.c > +++ b/drivers/xen/privcmd.c > @@ -557,7 +557,7 @@ static long privcmd_ioctl_mmap_batch( > state.global_error = 0; > state.version = version; > > - BUILD_BUG_ON(((PAGE_SIZE / sizeof(xen_pfn_t)) % XEN_PFN_PER_PAGE) != 0); > + BUILD_BUG_ON(((PAGE_SIZE_MIN / sizeof(xen_pfn_t)) % XEN_PFN_PER_PAGE_MAX) != 0); > /* mmap_batch_fn guarantees ret == 0 */ > BUG_ON(traverse_pages_block(m.num, sizeof(xen_pfn_t), > &pagelist, mmap_batch_fn, &state)); > diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c > index 51b3124b0d56c..99bde836c10c4 100644 > --- a/drivers/xen/xenbus/xenbus_client.c > +++ b/drivers/xen/xenbus/xenbus_client.c > @@ -49,9 +49,10 @@ > > #include "xenbus.h" > > -#define XENBUS_PAGES(_grants) (DIV_ROUND_UP(_grants, XEN_PFN_PER_PAGE)) > +#define XENBUS_PAGES(_grants) (DIV_ROUND_UP(_grants, XEN_PFN_PER_PAGE)) > +#define XENBUS_PAGES_MAX(_grants) (DIV_ROUND_UP(_grants, XEN_PFN_PER_PAGE_MIN)) > > -#define XENBUS_MAX_RING_PAGES (XENBUS_PAGES(XENBUS_MAX_RING_GRANTS)) > +#define XENBUS_MAX_RING_PAGES (XENBUS_PAGES_MAX(XENBUS_MAX_RING_GRANTS)) > > struct xenbus_map_node { > struct list_head next; > diff --git a/drivers/xen/xlate_mmu.c b/drivers/xen/xlate_mmu.c > index f17c4c03db30c..a757c801a7542 100644 > --- a/drivers/xen/xlate_mmu.c > +++ b/drivers/xen/xlate_mmu.c > @@ -74,9 +74,9 @@ struct remap_data { > int mapped; > > /* Hypercall parameters */ > - int h_errs[XEN_PFN_PER_PAGE]; > - xen_ulong_t h_idxs[XEN_PFN_PER_PAGE]; > - xen_pfn_t h_gpfns[XEN_PFN_PER_PAGE]; > + int h_errs[XEN_PFN_PER_PAGE_MAX]; > + xen_ulong_t h_idxs[XEN_PFN_PER_PAGE_MAX]; > + xen_pfn_t h_gpfns[XEN_PFN_PER_PAGE_MAX]; > > int h_iter; /* Iterator */ > }; > diff --git a/include/xen/page.h b/include/xen/page.h > index 285677b42943a..86683a30038a3 100644 > --- a/include/xen/page.h > +++ b/include/xen/page.h > @@ -21,6 +21,8 @@ > ((page_to_pfn(page)) << (PAGE_SHIFT - XEN_PAGE_SHIFT)) > > #define XEN_PFN_PER_PAGE (PAGE_SIZE / XEN_PAGE_SIZE) > +#define XEN_PFN_PER_PAGE_MIN (PAGE_SIZE_MIN / XEN_PAGE_SIZE) > +#define XEN_PFN_PER_PAGE_MAX (PAGE_SIZE_MAX / XEN_PAGE_SIZE) > > #define XEN_PFN_DOWN(x) ((x) >> XEN_PAGE_SHIFT) > #define XEN_PFN_UP(x) (((x) + XEN_PAGE_SIZE-1) >> XEN_PAGE_SHIFT)