| Message ID | 20230906073902.4229-3-adrian.hunter@intel.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Do not map unaccepted memory | expand |
On 9/6/23 00:39, Adrian Hunter wrote: > +static bool pfn_is_unaccepted_memory(unsigned long pfn) > +{ > + phys_addr_t paddr = pfn << PAGE_SHIFT; > + > + return range_contains_unaccepted_memory(paddr, paddr + PAGE_SIZE); > +} Please just add this as an inline helper to common code rather than copying and pasting two copies around the tree.
On 9/6/23 00:39, Adrian Hunter wrote: > Do not map unaccepted memory because it can cause the guest to fail. > > For /proc/kcore, which is read-only and does not support mmap, this means a > read of unaccepted memory will return zeros. I'm confused by this changelog and subject. What is getting "mapped" here if mmap() isn't in play?
diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c index 23fc24d16b31..a3091c5ed871 100644 --- a/fs/proc/kcore.c +++ b/fs/proc/kcore.c @@ -76,6 +76,13 @@ static int pfn_is_ram(unsigned long pfn) return 1; } +static bool pfn_is_unaccepted_memory(unsigned long pfn) +{ + phys_addr_t paddr = pfn << PAGE_SHIFT; + + return range_contains_unaccepted_memory(paddr, paddr + PAGE_SIZE); +} + /* This doesn't grab kclist_lock, so it should only be used at init time. */ void __init kclist_add(struct kcore_list *new, void *addr, size_t size, int type) @@ -546,7 +553,8 @@ static ssize_t read_kcore_iter(struct kiocb *iocb, struct iov_iter *iter) * and explicitly excluded physical ranges. */ if (!page || PageOffline(page) || - is_page_hwpoison(page) || !pfn_is_ram(pfn)) { + is_page_hwpoison(page) || !pfn_is_ram(pfn) || + pfn_is_unaccepted_memory(pfn)) { if (iov_iter_zero(tsz, iter) != tsz) { ret = -EFAULT; goto out;
Support for unaccepted memory was added recently, refer commit dcdfdd40fa82 ("mm: Add support for unaccepted memory"), whereby a virtual machine may need to accept memory before it can be used. Do not map unaccepted memory because it can cause the guest to fail. For /proc/kcore, which is read-only and does not support mmap, this means a read of unaccepted memory will return zeros. Fixes: dcdfdd40fa82 ("mm: Add support for unaccepted memory") Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> --- fs/proc/kcore.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)