Merge branch 'for-5.20/io_uring' into for-5.20/io_uring-zerocopy-send

* for-5.20/io_uring: (716 commits)
  io_uring: ensure REQ_F_ISREG is set async offload
  net: fix compat pointer in get_compat_msghdr()
  io_uring: Don't require reinitable percpu_ref
  io_uring: fix types in io_recvmsg_multishot_overflow
  io_uring: Use atomic_long_try_cmpxchg in __io_account_mem
  io_uring: support multishot in recvmsg
  net: copy from user before calling __get_compat_msghdr
  net: copy from user before calling __copy_msghdr
  io_uring: support 0 length iov in buffer select in compat
  io_uring: fix multishot ending when not polled
  io_uring: add netmsg cache
  io_uring: impose max limit on apoll cache
  io_uring: add abstraction around apoll cache
  io_uring: move apoll cache to poll.c
  io_uring: consolidate hash_locked io-wq handling
  io_uring: clear REQ_F_HASH_LOCKED on hash removal
  io_uring: don't race double poll setting REQ_F_ASYNC_DATA
  io_uring: don't miss setting REQ_F_DOUBLE_POLL
  io_uring: disable multishot recvmsg
  io_uring: only trace one of complete or overflow
  ...

Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 12 insertions, 2 deletions

diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index d8cfce221275..57ba5502aecf 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -77,10 +77,20 @@ static uint8_t __pte2cachemode_tbl[8] = {
 	[__pte2cm_idx(_PAGE_PWT | _PAGE_PCD | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC,
 };
 
-/* Check that the write-protect PAT entry is set for write-protect */
+/*
+ * Check that the write-protect PAT entry is set for write-protect.
+ * To do this without making assumptions how PAT has been set up (Xen has
+ * another layout than the kernel), translate the _PAGE_CACHE_MODE_WP cache
+ * mode via the __cachemode2pte_tbl[] into protection bits (those protection
+ * bits will select a cache mode of WP or better), and then translate the
+ * protection bits back into the cache mode using __pte2cm_idx() and the
+ * __pte2cachemode_tbl[] array. This will return the really used cache mode.
+ */
 bool x86_has_pat_wp(void)
 {
-	return __pte2cachemode_tbl[_PAGE_CACHE_MODE_WP] == _PAGE_CACHE_MODE_WP;
+	uint16_t prot = __cachemode2pte_tbl[_PAGE_CACHE_MODE_WP];
+
+	return __pte2cachemode_tbl[__pte2cm_idx(prot)] == _PAGE_CACHE_MODE_WP;
 }
 
 enum page_cache_mode pgprot2cachemode(pgprot_t pgprot)