From: Marc Rittinghaus <marc.rittinghaus@unikraft.io>
Date: Wed, 12 Apr 2023 12:55:03 +0000 (+0200)
Subject: lib/uksglist: Make sure buffers are mapped
X-Git-Tag: RELEASE-0.13.0~148
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=7f7f84e63390aa6dd1cfb848e26bd666d1478ede;p=unikraft%2Funikraft.git

lib/uksglist: Make sure buffers are mapped

With ukvmem and demand-paging enabled it can happen that buffers
supplied to the sglist are not fully backed by physical memory. In that
case the call to ukplat_virt_to_phys() fails, which expects a valid
mapping.

This commit adds a call to uk_vma_advise() to make sure the entire
buffer is backed by physical memory.

A future optimization should integrate the address translation and
backing with physical memory in a visitor pattern that traverses the
page tables only once instead of doing it one time for the advise and
then an extra time for each page of the buffer.

Signed-off-by: Marc Rittinghaus <marc.rittinghaus@unikraft.io>
Reviewed-by: Ioan-Teodor Teugea <teodor.teugea@gmail.com>
Reviewed-by: Razvan Deaconescu <razvand@unikraft.io>
Approved-by: Razvan Deaconescu <razvand@unikraft.io>
Tested-by: Unikraft CI <monkey@unikraft.io>
GitHub-Closes: #834
---

diff --git a/lib/uksglist/sglist.c b/lib/uksglist/sglist.c
index 65973d018..150de10a6 100644
--- a/lib/uksglist/sglist.c
+++ b/lib/uksglist/sglist.c
@@ -46,6 +46,10 @@
 #include <uk/alloc.h>
 #endif /* CONFIG_LIBUKALLOC */
 #include <uk/sglist.h>
+#ifdef CONFIG_LIBUKVMEM
+#include <uk/arch/paging.h>
+#include <uk/vmem.h>
+#endif /* CONFIG_LIBUKVMEM*/
 
 /*
  * Convenience macros to save the state of an sglist so it can be restored
@@ -125,9 +129,20 @@ static inline int _sglist_append_buf(struct uk_sglist *sg, void *buf,
 	if (len == 0)
 		return 0;
 
-	/* Do the first page.  It may have an offset. */
 	vaddr = (__vaddr_t)buf;
 	offset = page_off(vaddr);
+
+#ifdef CONFIG_LIBUKVMEM
+	/* Ensure the buffer is backed by physical memory */
+	error = uk_vma_advise(uk_vas_get_active(),
+			      PAGE_ALIGN_DOWN(vaddr),
+			      PAGE_ALIGN_UP(len + offset), UK_VMA_ADV_WILLNEED,
+			      UK_VMA_FLAG_UNINITIALIZED);
+	if (unlikely(error))
+		return error;
+#endif /* CONFIG_LIBUKVMEM */
+
+	/* Do the first page. It may have an offset. */
 	paddr = ukplat_virt_to_phys((void *)vaddr);
 	seglen = MIN(len, __PAGE_SIZE - offset);
 	if (sg->sg_nseg == 0) {