+Julien On Wed, 16 Oct 2024, Ryan Roberts wrote: > + 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@xxxxxxx/ > > > 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 <ryan.roberts@xxxxxxx> > > --- > > > > ***NOTE*** > > Any confused maintainers may want to read the cover note here for context: > > https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@xxxxxxx/ > > > > 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); Is there any value in keep this test? And if so, what should it look like? I think we should turn it into a WARN_ON: WARN_ON(((PAGE_SIZE / sizeof(xen_pfn_t)) % XEN_PFN_PER_PAGE) != 0); It doesn't make much sense having a BUILD_BUG_ON on a variable that can change? > > /* 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) >
