linux-kernel - [PATCH 2/2] IB/rdmavt: modify rdmavt/qp.c for UML

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Date:   Sat,  1 Jan 2022 23:06:23 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     linux-kernel@...r.kernel.org, Jason Gunthorpe <jgg@...dia.com>,
        Jeff Dike <jdike@...toit.com>,
        Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>
Cc:     linux-rdma@...r.kernel.org, linux-um@...ts.infradead.org,
        Randy Dunlap <rdunlap@...radead.org>
Subject: [PATCH 2/2] IB/rdmavt: modify rdmavt/qp.c for UML

When building rdmavt for ARCH=um, qp.c has a build error on a reference
to the x86-specific cpuinfo field 'x86_cache_size'. This value is then
used to determine whether to use cacheless_memcpy() or not.
Provide a fake value to LLC for CONFIG_UML. Then provide a separate
verison of cacheless_memcpy() for CONFIG_UML that is just a plain
memcpy(), like the calling code uses.

Prevents these build errors:

../drivers/infiniband/sw/rdmavt/qp.c: In function ‘rvt_wss_llc_size’:
../drivers/infiniband/sw/rdmavt/qp.c:88:23: error: ‘struct cpuinfo_um’ has no member named ‘x86_cache_size’; did you mean ‘x86_capability’?
  return boot_cpu_data.x86_cache_size;

../drivers/infiniband/sw/rdmavt/qp.c: In function ‘cacheless_memcpy’:
../drivers/infiniband/sw/rdmavt/qp.c:100:2: error: implicit declaration of function ‘__copy_user_nocache’; did you mean ‘copy_user_page’? [-Werror=implicit-function-declaration]
  __copy_user_nocache(dst, (void __user *)src, n, 0);

Fixes: 68f5d3f3b654 ("um: add PCI over virtio emulation driver")
Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
---
 drivers/infiniband/sw/rdmavt/qp.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

--- linux-next-20211224.orig/drivers/infiniband/sw/rdmavt/qp.c
+++ linux-next-20211224/drivers/infiniband/sw/rdmavt/qp.c
@@ -84,10 +84,15 @@ EXPORT_SYMBOL(ib_rvt_state_ops);
 /* platform specific: return the last level cache (llc) size, in KiB */
 static int rvt_wss_llc_size(void)
 {
+#if !defined(CONFIG_UML)
 	/* assume that the boot CPU value is universal for all CPUs */
 	return boot_cpu_data.x86_cache_size;
+#else /* CONFIG_UML */
+	return 1024;	/* fake 1 MB LLC size */
+#endif
 }

+#if !defined(CONFIG_UML)
 /* platform specific: cacheless copy */
 static void cacheless_memcpy(void *dst, void *src, size_t n)
 {
@@ -99,6 +104,13 @@ static void cacheless_memcpy(void *dst,
 	 */
 	__copy_user_nocache(dst, (void __user *)src, n, 0);
 }
+#else
+/* for CONFIG_UML, this is just a plain memcpy() */
+static void cacheless_memcpy(void *dst, void *src, size_t n)
+{
+	memcpy(dst, src, n);
+}
+#endif

 void rvt_wss_exit(struct rvt_dev_info *rdi)
 {