[PATCH v8 3/7] xen/console: switch conring runtime allocation to xvmalloc

[dmukhin@xxxxxxxx]

From: Denis Mukhin <dmukhin@xxxxxxxx> 

The console ring only needs to be virtually contiguous; it does not need
a naturally aligned or physically contiguous allocation. Replace the
runtime xenheap allocation in console_init_ring() with an xvmalloc-backed
buffer.

Also clamp the user-configured ring size to the supported range and emit
warning when the requested size is adjusted.

Drop full stops in all diagnostic messages in console_init_ring() to align
code with the common code pattern.

Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Denis Mukhin <dmukhin@xxxxxxxx>
---
Changes since v7:
- Jan's feedback from
  
https://lore.kernel.org/xen-devel/0fefa50c-46aa-4ede-a8e2-8c2c619bc2ab@xxxxxxxx/
---
 xen/drivers/char/console.c | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index 40355c1d14d6..09282a7a4f8e 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -33,6 +33,7 @@
 #include <asm/setup.h>
 #include <xen/sections.h>
 #include <xen/consoled.h>
+#include <xen/xvmalloc.h>
 
 #ifdef CONFIG_X86
 #include <asm/guest.h>
@@ -464,20 +465,30 @@ void __init console_init_ring(void)
 {
     char *ring;
     unsigned int done, size, n;
-    unsigned int order, memflags;
     unsigned long flags;
 
     if ( !opt_conring_size )
         return;
 
-    order = get_order_from_bytes(max(opt_conring_size, conring_size));
-    memflags = MEMF_bits(crashinfo_maxaddr_bits);
-    while ( (ring = alloc_xenheap_pages(order, memflags)) == NULL )
+    if ( opt_conring_size < GB(2) )
     {
-        BUG_ON(order == 0);
-        order--;
+        unsigned int order = get_order_from_bytes(max(opt_conring_size,
+                                                      conring_size));
+
+        opt_conring_size = PAGE_SIZE << order;
+    }
+    else
+    {
+        printk(XENLOG_WARNING
+               "Limiting user-configured console ring size to 2 GiB\n");
+        opt_conring_size = GB(2);
+    }
+
+    while ( (ring = xvmalloc_array(char, opt_conring_size)) == NULL )
+    {
+        BUG_ON(opt_conring_size == 0);
+        opt_conring_size >>= 1;
     }
-    opt_conring_size = PAGE_SIZE << order;
 
     nrspin_lock_irqsave(&console_lock, flags);
 
@@ -498,7 +509,7 @@ void __init console_init_ring(void)
     conring_size = opt_conring_size;
     nrspin_unlock_irqrestore(&console_lock, flags);
 
-    printk("Allocated console ring of %u KiB.\n", opt_conring_size >> 10);
+    printk("Allocated console ring of %u KiB\n", opt_conring_size >> 10);
 }
 
 /*
-- 
2.54.0