| Message ID | 20190529090407.1225-4-jgross@suse.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | xen/swiotlb: fix an issue and improve swiotlb-xen | expand |
>>> On 29.05.19 at 11:04, <jgross@suse.com> wrote: > @@ -345,8 +346,11 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr, > size = 1UL << (order + XEN_PAGE_SHIFT); > > if (!WARN_ON((dev_addr + size - 1 > dma_mask) || > - range_straddles_page_boundary(phys, size))) > + range_straddles_page_boundary(phys, size)) && > + PageXenRemapped(virt_to_page(vaddr))) { > xen_destroy_contiguous_region(phys, order); > + ClearPageXenRemapped(virt_to_page(vaddr)); > + } To be symmetric with setting the flag only after having made the region contiguous, and to avoid (perhaps just theoretical) races, wouldn't it be better to clear the flag before calling xen_destroy_contiguous_region()? Even better would be a TestAndClear...() operation. Jan
On 29/05/2019 11:57, Jan Beulich wrote: >>>> On 29.05.19 at 11:04, <jgross@suse.com> wrote: >> @@ -345,8 +346,11 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr, >> size = 1UL << (order + XEN_PAGE_SHIFT); >> >> if (!WARN_ON((dev_addr + size - 1 > dma_mask) || >> - range_straddles_page_boundary(phys, size))) >> + range_straddles_page_boundary(phys, size)) && >> + PageXenRemapped(virt_to_page(vaddr))) { >> xen_destroy_contiguous_region(phys, order); >> + ClearPageXenRemapped(virt_to_page(vaddr)); >> + } > > To be symmetric with setting the flag only after having made the region > contiguous, and to avoid (perhaps just theoretical) races, wouldn't it be > better to clear the flag before calling xen_destroy_contiguous_region()? > Even better would be a TestAndClear...() operation. I like that idea. Juergen
Please don't add your private flag to page-flags.h. The whole point of the private flag is that you can use it in any way you want withou touching the common code.
On 5/30/19 5:04 AM, Christoph Hellwig wrote: > Please don't add your private flag to page-flags.h. The whole point of > the private flag is that you can use it in any way you want withou > touching the common code. There is already a bunch of aliases for various sub-components (including Xen) in page-flags.h for private flags, which is why I suggested we do the same for the new use case. Adding this new alias will keep flag usage consistent. -boris
On 30/05/2019 14:46, Boris Ostrovsky wrote: > On 5/30/19 5:04 AM, Christoph Hellwig wrote: >> Please don't add your private flag to page-flags.h. The whole point of >> the private flag is that you can use it in any way you want withou >> touching the common code. > > > There is already a bunch of aliases for various sub-components > (including Xen) in page-flags.h for private flags, which is why I > suggested we do the same for the new use case. Adding this new alias > will keep flag usage consistent. What about me adding another patch moving those Xen private aliases into arch/x86/include/asm/xen/page.h ? Juergen
On 31.05.19 13:38, Juergen Gross wrote: > On 30/05/2019 14:46, Boris Ostrovsky wrote: >> On 5/30/19 5:04 AM, Christoph Hellwig wrote: >>> Please don't add your private flag to page-flags.h. The whole point of >>> the private flag is that you can use it in any way you want withou >>> touching the common code. >> >> >> There is already a bunch of aliases for various sub-components >> (including Xen) in page-flags.h for private flags, which is why I >> suggested we do the same for the new use case. Adding this new alias >> will keep flag usage consistent. > > What about me adding another patch moving those Xen private aliases > into arch/x86/include/asm/xen/page.h ? This is becoming difficult. I'd need to remove the "#undef PF_NO_COMPOUND" from page-flags.h or to #include a (new) xen/page-flags.h from page-flags.h after all the defines are ready. Is that really worth the effort given that other components (e.g. file systems) are doing the same? Juergen
diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c index aba5247b9145..7e2d9d1b6f63 100644 --- a/drivers/xen/swiotlb-xen.c +++ b/drivers/xen/swiotlb-xen.c @@ -321,6 +321,7 @@ xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size, xen_free_coherent_pages(hwdev, size, ret, (dma_addr_t)phys, attrs); return NULL; } + SetPageXenRemapped(virt_to_page(ret)); } memset(ret, 0, size); return ret; @@ -345,8 +346,11 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr, size = 1UL << (order + XEN_PAGE_SHIFT); if (!WARN_ON((dev_addr + size - 1 > dma_mask) || - range_straddles_page_boundary(phys, size))) + range_straddles_page_boundary(phys, size)) && + PageXenRemapped(virt_to_page(vaddr))) { xen_destroy_contiguous_region(phys, order); + ClearPageXenRemapped(virt_to_page(vaddr)); + } xen_free_coherent_pages(hwdev, size, vaddr, (dma_addr_t)phys, attrs); } diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 9f8712a4b1a5..296480e990f2 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -152,6 +152,8 @@ enum pageflags { PG_savepinned = PG_dirty, /* Has a grant mapping of another (foreign) domain's page. */ PG_foreign = PG_owner_priv_1, + /* Remapped by swiotlb-xen. */ + PG_xen_remapped = PG_owner_priv_1, /* SLOB */ PG_slob_free = PG_private, @@ -329,6 +331,7 @@ PAGEFLAG(Pinned, pinned, PF_NO_COMPOUND) TESTSCFLAG(Pinned, pinned, PF_NO_COMPOUND) PAGEFLAG(SavePinned, savepinned, PF_NO_COMPOUND); PAGEFLAG(Foreign, foreign, PF_NO_COMPOUND); +PAGEFLAG(XenRemapped, xen_remapped, PF_NO_COMPOUND); PAGEFLAG(Reserved, reserved, PF_NO_COMPOUND) __CLEARPAGEFLAG(Reserved, reserved, PF_NO_COMPOUND)
Instead of always calling xen_destroy_contiguous_region() in case the memory is DMA-able for the used device, do so only in case it has been made DMA-able via xen_create_contiguous_region() before. This will avoid a lot of xen_destroy_contiguous_region() calls for 64-bit capable devices. As the memory in question is owned by swiotlb-xen the PG_owner_priv_1 flag of the first allocated page can be used for remembering. Signed-off-by: Juergen Gross <jgross@suse.com> --- V2: add PG_xen_remapped alias for PG_owner_priv_1 (Boris Ostrovsky) only clear page flag in case of sane conditions (Jan Beulich) --- drivers/xen/swiotlb-xen.c | 6 +++++- include/linux/page-flags.h | 3 +++ 2 files changed, 8 insertions(+), 1 deletion(-)