intel_th: avoid using deprecated page->mapping, index fields

The struct page->mapping, index fields are deprecated and soon to be only
available as part of a folio.

It is likely the intel_th code which sets page->mapping, index is was
implemented out of concern that some aspect of the page fault logic may
encounter unexpected problems should they not.

However, the appropriate interface for inserting kernel-allocated memory is
vm_insert_page() in a VM_MIXEDMAP. By using the helper function
vmf_insert_mixed() we can do this with minimal churn in the existing fault
handler.

By doing so, we bypass the remainder of the faulting logic. The pages are
still pinned so there is no possibility of anything unexpected being done
with the pages once established.

It would also be reasonable to pre-map everything on fault, however to
minimise churn we retain the fault handler.

We also eliminate all code which clears page->mapping on teardown as this
has now become unnecessary.

The MSU code relies on faulting to function correctly, so is by definition
dependent on CONFIG_MMU. We avoid spurious reports about compilation
failure for unsupported platforms by making this requirement explicit in
Kconfig as part of this change too.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Link: https://lore.kernel.org/r/20250331125608.60300-1-lorenzo.stoakes@oracle.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hwtracing/intel_th/Kconfig b/drivers/hwtracing/intel_th/Kconfig
index 4b6359326ede99ada4ad543fa20f4a742b17420c..4f7d2b6d79e294ec0253f1a7bd7bf64afa993450 100644 (file)
--- a/drivers/hwtracing/intel_th/Kconfig
+++ b/drivers/hwtracing/intel_th/Kconfig
@@ -60,6 +60,7 @@ config INTEL_TH_STH
 
 config INTEL_TH_MSU
        tristate "Intel(R) Trace Hub Memory Storage Unit"
+       depends on MMU
        help
          Memory Storage Unit (MSU) trace output device enables
          storing STP traces to system memory. It supports single

diff --git a/drivers/hwtracing/intel_th/msu.c b/drivers/hwtracing/intel_th/msu.c
index bf99d79a41920491480ac21d607ccc7d12141661..7163950eb3719ca10f3916deb09b1a624a87fd40 100644 (file)
--- a/drivers/hwtracing/intel_th/msu.c
+++ b/drivers/hwtracing/intel_th/msu.c
@@ -19,6 +19,7 @@
 #include <linux/io.h>
 #include <linux/workqueue.h>
 #include <linux/dma-mapping.h>
+#include <linux/pfn_t.h>
 
 #ifdef CONFIG_X86
 #include <asm/set_memory.h>
@@ -976,7 +977,6 @@ static void msc_buffer_contig_free(struct msc *msc)
        for (off = 0; off < msc->nr_pages << PAGE_SHIFT; off += PAGE_SIZE) {
                struct page *page = virt_to_page(msc->base + off);
 
-               page->mapping = NULL;
                __free_page(page);
        }
 
@@ -1158,9 +1158,6 @@ static void __msc_buffer_win_free(struct msc *msc, struct msc_window *win)
        int i;
 
        for_each_sg(win->sgt->sgl, sg, win->nr_segs, i) {
-               struct page *page = msc_sg_page(sg);
-
-               page->mapping = NULL;
                dma_free_coherent(msc_dev(win->msc)->parent->parent, PAGE_SIZE,
                                  sg_virt(sg), sg_dma_address(sg));
        }
@@ -1601,22 +1598,10 @@ static void msc_mmap_close(struct vm_area_struct *vma)
 {
        struct msc_iter *iter = vma->vm_file->private_data;
        struct msc *msc = iter->msc;
-       unsigned long pg;
 
        if (!atomic_dec_and_mutex_lock(&msc->mmap_count, &msc->buf_mutex))
                return;
 
-       /* drop page _refcounts */
-       for (pg = 0; pg < msc->nr_pages; pg++) {
-               struct page *page = msc_buffer_get_page(msc, pg);
-
-               if (WARN_ON_ONCE(!page))
-                       continue;
-
-               if (page->mapping)
-                       page->mapping = NULL;
-       }
-
        /* last mapping -- drop user_count */
        atomic_dec(&msc->user_count);
        mutex_unlock(&msc->buf_mutex);
@@ -1626,16 +1611,14 @@ static vm_fault_t msc_mmap_fault(struct vm_fault *vmf)
 {
        struct msc_iter *iter = vmf->vma->vm_file->private_data;
        struct msc *msc = iter->msc;
+       struct page *page;
 
-       vmf->page = msc_buffer_get_page(msc, vmf->pgoff);
-       if (!vmf->page)
+       page = msc_buffer_get_page(msc, vmf->pgoff);
+       if (!page)
                return VM_FAULT_SIGBUS;
 
-       get_page(vmf->page);
-       vmf->page->mapping = vmf->vma->vm_file->f_mapping;
-       vmf->page->index = vmf->pgoff;
-
-       return 0;
+       get_page(page);
+       return vmf_insert_mixed(vmf->vma, vmf->address, page_to_pfn_t(page));
 }
 
 static const struct vm_operations_struct msc_mmap_ops = {
@@ -1676,7 +1659,7 @@ out:
                atomic_dec(&msc->user_count);
 
        vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
-       vm_flags_set(vma, VM_DONTEXPAND | VM_DONTCOPY);
+       vm_flags_set(vma, VM_DONTEXPAND | VM_DONTCOPY | VM_MIXEDMAP);
        vma->vm_ops = &msc_mmap_ops;
        return ret;
 }