| Message ID | 20241014105912.3207374-36-ryan.roberts@arm.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Boot-time page size selection for arm64 | expand |
+ 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 <ryan.roberts@arm.com> > --- > > ***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)
+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@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 <ryan.roberts@arm.com> > > --- > > > > ***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); 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) >
On 23/10/2024 02:23, Stefano Stabellini wrote: > +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@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 <ryan.roberts@arm.com> >>> --- >>> >>> ***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); > > 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? I believe that as long as we assume sizeof(xen_pfn_t), PAGE_SIZE and XEN_PAGE_SIZE are all power-of-two sizes, then this single build-time test should cover all possible boot-time PAGE_SIZEs. Logic: If PAGE_SIZE and XEN_PAGE_SIZE are power-of-two, then XEN_PFN_PER_PAGE must also be power-of-two. XEN_PFN_PER_PAGE_MAX is just the worst case limit. (PAGE_SIZE_MIN / sizeof(xen_pfn_t)) is the number of xen_pfn_t that fit on smallest page. If you can get an integer multiple number of XEN_PFN_PER_PAGE_MAX on the smallest page, then it remains an integer multiple as PAGE_SIZE gets bigger, assuming it is restricted to power-of-two sizes. Perhaps there is a floor in my logic? I'd prefer to keep BUILD_BUG_ON where possible to avoid the additional image size bloat and runtime costs. Thanks, Ryan > > >>> /* 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) >>
On Thu, 24 Oct 2024, Ryan Roberts wrote: > On 23/10/2024 02:23, Stefano Stabellini wrote: > > +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@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 <ryan.roberts@arm.com> > >>> --- > >>> > >>> ***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); > > > > 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? > > I believe that as long as we assume sizeof(xen_pfn_t), PAGE_SIZE and > XEN_PAGE_SIZE are all power-of-two sizes, then this single build-time test > should cover all possible boot-time PAGE_SIZEs. > > Logic: > > If PAGE_SIZE and XEN_PAGE_SIZE are power-of-two, then XEN_PFN_PER_PAGE must also > be power-of-two. XEN_PFN_PER_PAGE_MAX is just the worst case limit. > > (PAGE_SIZE_MIN / sizeof(xen_pfn_t)) is the number of xen_pfn_t that fit on > smallest page. > > If you can get an integer multiple number of XEN_PFN_PER_PAGE_MAX on the > smallest page, then it remains an integer multiple as PAGE_SIZE gets bigger, > assuming it is restricted to power-of-two sizes. > > Perhaps there is a floor in my logic? > > I'd prefer to keep BUILD_BUG_ON where possible to avoid the additional image > size bloat and runtime costs. You are right. It would be nice to add a in-code comment to explain this. Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> > >>> /* 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) > >> >
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)
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@arm.com> --- ***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(-)