[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH] xen/virtio: Convert PAGE_SIZE/PAGE_SHIFT/PFN_UP to Xen counterparts
On 06.10.22 20:59, Xenia Ragiadakou wrote: Hello Xenia > > On 10/6/22 15:09, Oleksandr Tyshchenko wrote: >> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx> >> >> Although XEN_PAGE_SIZE is equal to PAGE_SIZE (4KB) for now, it would >> be more correct to use Xen specific #define-s as XEN_PAGE_SIZE can >> be changed at some point in the future. >> >> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx> >> --- >> Cc: Juergen Gross <jgross@xxxxxxxx> >> Cc: Xenia Ragiadakou <burzalodowa@xxxxxxxxx> >> >> As it was proposed at: >> https://urldefense.com/v3/__https://lore.kernel.org/xen-devel/20221005174823.1800761-1-olekstysh@xxxxxxxxx/__;!!GF_29dbcQIUBPA!zHt-xZ_7tZc_EM6zva21E_YgwIiEeimFWfsJIpPwAu-TBcnzQhXHqlKzmXmwIcI6uIx_arHNZiaZeHt_428_8p-DyMpd$ >> >> [lore[.]kernel[.]org] >> >> Should go in only after that series. >> --- >> drivers/xen/grant-dma-ops.c | 20 ++++++++++---------- >> 1 file changed, 10 insertions(+), 10 deletions(-) >> >> diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c >> index c66f56d24013..5392fdc25dca 100644 >> --- a/drivers/xen/grant-dma-ops.c >> +++ b/drivers/xen/grant-dma-ops.c >> @@ -31,12 +31,12 @@ static DEFINE_XARRAY_FLAGS(xen_grant_dma_devices, >> XA_FLAGS_LOCK_IRQ); >> static inline dma_addr_t grant_to_dma(grant_ref_t grant) >> { >> - return XEN_GRANT_DMA_ADDR_OFF | ((dma_addr_t)grant << PAGE_SHIFT); >> + return XEN_GRANT_DMA_ADDR_OFF | ((dma_addr_t)grant << >> XEN_PAGE_SHIFT); >> } > > With this change, can the offset added to the dma handle, generated by > grant_to_dma(), be the offset in the page? Couldn't it corrupt the > grant ref? Good point, indeed, I think it could corrupt if guest uses a different than Xen page granularity (i.e 64KB). > >> static inline grant_ref_t dma_to_grant(dma_addr_t dma) >> { >> - return (grant_ref_t)((dma & ~XEN_GRANT_DMA_ADDR_OFF) >> >> PAGE_SHIFT); >> + return (grant_ref_t)((dma & ~XEN_GRANT_DMA_ADDR_OFF) >> >> XEN_PAGE_SHIFT); >> } >> static struct xen_grant_dma_data *find_xen_grant_dma_data(struct >> device *dev) >> @@ -79,7 +79,7 @@ static void *xen_grant_dma_alloc(struct device >> *dev, size_t size, >> unsigned long attrs) >> { >> struct xen_grant_dma_data *data; >> - unsigned int i, n_pages = PFN_UP(size); >> + unsigned int i, n_pages = XEN_PFN_UP(size); >> unsigned long pfn; >> grant_ref_t grant; >> void *ret; >> @@ -91,14 +91,14 @@ static void *xen_grant_dma_alloc(struct device >> *dev, size_t size, >> if (unlikely(data->broken)) >> return NULL; >> - ret = alloc_pages_exact(n_pages * PAGE_SIZE, gfp); >> + ret = alloc_pages_exact(n_pages * XEN_PAGE_SIZE, gfp); >> if (!ret) >> return NULL; >> pfn = virt_to_pfn(ret); >> if (gnttab_alloc_grant_reference_seq(n_pages, &grant)) { >> - free_pages_exact(ret, n_pages * PAGE_SIZE); >> + free_pages_exact(ret, n_pages * XEN_PAGE_SIZE); >> return NULL; >> } >> @@ -116,7 +116,7 @@ static void xen_grant_dma_free(struct device >> *dev, size_t size, void *vaddr, >> dma_addr_t dma_handle, unsigned long attrs) >> { >> struct xen_grant_dma_data *data; >> - unsigned int i, n_pages = PFN_UP(size); >> + unsigned int i, n_pages = XEN_PFN_UP(size); >> grant_ref_t grant; >> data = find_xen_grant_dma_data(dev); >> @@ -138,7 +138,7 @@ static void xen_grant_dma_free(struct device >> *dev, size_t size, void *vaddr, >> gnttab_free_grant_reference_seq(grant, n_pages); >> - free_pages_exact(vaddr, n_pages * PAGE_SIZE); >> + free_pages_exact(vaddr, n_pages * XEN_PAGE_SIZE); >> } >> static struct page *xen_grant_dma_alloc_pages(struct device *dev, >> size_t size, >> @@ -168,7 +168,7 @@ static dma_addr_t xen_grant_dma_map_page(struct >> device *dev, struct page *page, >> unsigned long attrs) >> { >> struct xen_grant_dma_data *data; >> - unsigned int i, n_pages = PFN_UP(offset + size); >> + unsigned int i, n_pages = XEN_PFN_UP(offset + size); > > The offset, here, refers to the offset in the page ... > >> grant_ref_t grant; >> dma_addr_t dma_handle; >> @@ -200,8 +200,8 @@ static void xen_grant_dma_unmap_page(struct >> device *dev, dma_addr_t dma_handle, >> unsigned long attrs) >> { >> struct xen_grant_dma_data *data; >> - unsigned long offset = dma_handle & (PAGE_SIZE - 1); >> - unsigned int i, n_pages = PFN_UP(offset + size); >> + unsigned long offset = dma_handle & ~XEN_PAGE_MASK; > > ... while, here, it refers to the offset in the grant. > So, the calculated number of grants may differ. Good point, I think you are right, so we need to additionally use xen_offset_in_page() macro in xen_grant_dma_map_page(), something like that to be squashed with current patch: diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c index 9d5eca6d638a..bb984dc05deb 100644 --- a/drivers/xen/grant-dma-ops.c +++ b/drivers/xen/grant-dma-ops.c @@ -169,7 +169,7 @@ static dma_addr_t xen_grant_dma_map_page(struct device *dev, struct page *page, unsigned long attrs) { struct xen_grant_dma_data *data; - unsigned int i, n_pages = XEN_PFN_UP(offset + size); + unsigned int i, n_pages = XEN_PFN_UP(xen_offset_in_page(offset) + size); grant_ref_t grant; dma_addr_t dma_handle; @@ -191,7 +191,7 @@ static dma_addr_t xen_grant_dma_map_page(struct device *dev, struct page *page, xen_page_to_gfn(page) + i, dir == DMA_TO_DEVICE); } - dma_handle = grant_to_dma(grant) + offset; + dma_handle = grant_to_dma(grant) + xen_offset_in_page(offset); return dma_handle; } Did I get your point right? > > >> + unsigned int i, n_pages = XEN_PFN_UP(offset + size); >> grant_ref_t grant; >> if (WARN_ON(dir == DMA_NONE)) > Thank you. -- Regards, Oleksandr Tyshchenko
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