[PATCH 1 of 5 v4] common/sysctl: Introduce hypercall to query the console ring size

[PATCH 1 of 5 v4] common/sysctl: Introduce hypercall to query the console ring size

[Andrew Cooper]

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

--
Changes since v2:
 * Rebase on top of coverage patches.
 * Reword hypercall comments.

diff -r a6b81234b189 -r 89f3c6846f6b xen/common/sysctl.c
--- a/xen/common/sysctl.c
+++ b/xen/common/sysctl.c
@@ -358,6 +358,10 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xe
     }
     break;
 
+    case XEN_SYSCTL_consoleringsize:
+        ret = console_ring_size(&op->u.consoleringsize);
+        break;
+
 #ifdef TEST_COVERAGE
     case XEN_SYSCTL_coverage_op:
         ret = sysctl_coverage_op(&op->u.coverage_op);
diff -r a6b81234b189 -r 89f3c6846f6b xen/drivers/char/console.c
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -226,6 +226,12 @@ long read_console_ring(struct xen_sysctl
     return 0;
 }
 
+long console_ring_size(struct xen_sysctl_consoleringsize * op)
+{
+    op->size = conring_size;
+    return 0;
+}
+
 
 /*
  * *******************************************************
diff -r a6b81234b189 -r 89f3c6846f6b xen/include/public/sysctl.h
--- a/xen/include/public/sysctl.h
+++ b/xen/include/public/sysctl.h
@@ -632,6 +632,14 @@ typedef struct xen_sysctl_coverage_op xe
 DEFINE_XEN_GUEST_HANDLE(xen_sysctl_coverage_op_t);
 
 
+/* XEN_SYSCTL_consoleringsize */
+/* Get the size of the hypervisor console ring in bytes. */
+struct xen_sysctl_consoleringsize {
+    uint64_t size; /* OUT */
+};
+typedef struct xen_sysctl_consoleringsize xen_sysctl_consoleringsize_t;
+DEFINE_XEN_GUEST_HANDLE(xen_sysctl_consoleringsize_t);
+
 struct xen_sysctl {
     uint32_t cmd;
 #define XEN_SYSCTL_readconsole                    1
@@ -653,6 +661,7 @@ struct xen_sysctl {
 #define XEN_SYSCTL_cpupool_op                    18
 #define XEN_SYSCTL_scheduler_op                  19
 #define XEN_SYSCTL_coverage_op                   20
+#define XEN_SYSCTL_consoleringsize               21
     uint32_t interface_version; /* XEN_SYSCTL_INTERFACE_VERSION */
     union {
         struct xen_sysctl_readconsole       readconsole;
@@ -674,6 +683,7 @@ struct xen_sysctl {
         struct xen_sysctl_cpupool_op        cpupool_op;
         struct xen_sysctl_scheduler_op      scheduler_op;
         struct xen_sysctl_coverage_op       coverage_op;
+        struct xen_sysctl_consoleringsize   consoleringsize;
         uint8_t                             pad[128];
     } u;
 };
diff -r a6b81234b189 -r 89f3c6846f6b xen/include/xen/console.h
--- a/xen/include/xen/console.h
+++ b/xen/include/xen/console.h
@@ -12,6 +12,8 @@
 
 struct xen_sysctl_readconsole;
 long read_console_ring(struct xen_sysctl_readconsole *op);
+struct xen_sysctl_consoleringsize;
+long console_ring_size(struct xen_sysctl_consoleringsize *op);
 
 void console_init_preirq(void);
 void console_init_postirq(void);

[PATCH 2 of 5 v4] tools/libxc: Helper function for XEN_SYSCTL_consoleringsize

[Andrew Cooper]

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

---
Changes since v2:
 * Tweak style and errno in case of invalid pointer.

diff -r 89f3c6846f6b -r 0bd32c19873e tools/libxc/xc_misc.c
--- a/tools/libxc/xc_misc.c
+++ b/tools/libxc/xc_misc.c
@@ -100,6 +100,26 @@ int xc_readconsolering(xc_interface *xch
     return ret;
 }
 
+int xc_consoleringsize(xc_interface *xch, uint64_t *psize)
+{
+    int ret = -1;
+    DECLARE_SYSCTL;
+
+    if ( !psize )
+    {
+        errno = EINVAL;
+        return ret;
+    }
+
+    sysctl.cmd = XEN_SYSCTL_consoleringsize;
+    ret = do_sysctl(xch, &sysctl);
+
+    if ( !ret )
+        *psize = sysctl.u.consoleringsize.size;
+
+    return ret;
+}
+
 int xc_send_debug_keys(xc_interface *xch, char *keys)
 {
     int ret, len = strlen(keys);
diff -r 89f3c6846f6b -r 0bd32c19873e tools/libxc/xenctrl.h
--- a/tools/libxc/xenctrl.h
+++ b/tools/libxc/xenctrl.h
@@ -998,6 +998,7 @@ int xc_readconsolering(xc_interface *xch
                        char *buffer,
                        unsigned int *pnr_chars,
                        int clear, int incremental, uint32_t *pindex);
+int xc_consoleringsize(xc_interface *xch, uint64_t *psize);
 
 int xc_send_debug_keys(xc_interface *xch, char *keys);

[PATCH 3 of 5 v4] tools/libxc: Implement xc_readconsolering_buffer()

[Andrew Cooper]

Functions identically to xc_readconsolering(), but uses a user-provided
xc_hypercall_buffer_t to save using a bounce buffer.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

--
Changes since v2:
 * Document xc_readconsolering() and xc_readconsolering_buffer() functions
Changes since v1:
 * Reduce xc_readconsolering() to use xc_readconsolering_buffer()

diff -r 0bd32c19873e -r c7b82dfbec34 tools/libxc/xc_misc.c
--- a/tools/libxc/xc_misc.c
+++ b/tools/libxc/xc_misc.c
@@ -70,13 +70,29 @@ int xc_readconsolering(xc_interface *xch
                        int clear, int incremental, uint32_t *pindex)
 {
     int ret;
-    unsigned int nr_chars = *pnr_chars;
-    DECLARE_SYSCTL;
-    DECLARE_HYPERCALL_BOUNCE(buffer, nr_chars, XC_HYPERCALL_BUFFER_BOUNCE_OUT);
+    DECLARE_HYPERCALL_BOUNCE(buffer, *pnr_chars, XC_HYPERCALL_BUFFER_BOUNCE_OUT);
 
     if ( xc_hypercall_bounce_pre(xch, buffer) )
         return -1;
 
+    ret = xc_readconsolering_buffer(xch, HYPERCALL_BUFFER(buffer),
+                                    pnr_chars, clear, incremental, pindex);
+
+    xc_hypercall_bounce_post(xch, buffer);
+
+    return ret;
+}
+
+int xc_readconsolering_buffer(xc_interface *xch,
+                              xc_hypercall_buffer_t *buffer,
+                              unsigned int *pnr_chars,
+                              int clear, int incremental, uint32_t *pindex)
+{
+    int ret;
+    unsigned int nr_chars = *pnr_chars;
+    DECLARE_SYSCTL;
+    DECLARE_HYPERCALL_BUFFER_ARGUMENT(buffer);
+
     sysctl.cmd = XEN_SYSCTL_readconsole;
     set_xen_guest_handle(sysctl.u.readconsole.buffer, buffer);
     sysctl.u.readconsole.count = nr_chars;
@@ -95,8 +111,6 @@ int xc_readconsolering(xc_interface *xch
             *pindex = sysctl.u.readconsole.index;
     }
 
-    xc_hypercall_bounce_post(xch, buffer);
-
     return ret;
 }
 
diff -r 0bd32c19873e -r c7b82dfbec34 tools/libxc/xenctrl.h
--- a/tools/libxc/xenctrl.h
+++ b/tools/libxc/xenctrl.h
@@ -994,10 +994,26 @@ int xc_physdev_pci_access_modify(xc_inte
                                  int func,
                                  int enable);
 
+/*
+ * For both readconsolering functions, *pnr_chars is both an input and
+ * output.  As an input, it specifies the size of *buffer, and as an output
+ * indicates now many character Xen wrote into *buffer.
+ *
+ * The 'clear' parameter indicates whether Xen should clear the buffer or not.
+ * If incremental is set, *pindex is an input and output parameter to aid with
+ * sequential small reads of the console ring.
+ *
+ * xc_readconsolering_buffer is preferred to avoid an extra copy of the console
+ * ring buffer.
+ */
 int xc_readconsolering(xc_interface *xch,
                        char *buffer,
                        unsigned int *pnr_chars,
                        int clear, int incremental, uint32_t *pindex);
+int xc_readconsolering_buffer(xc_interface *xch,
+                              xc_hypercall_buffer_t *buffer,
+                              unsigned int *pnr_chars,
+                              int clear, int incremental, uint32_t *pindex);
 int xc_consoleringsize(xc_interface *xch, uint64_t *psize);
 
 int xc_send_debug_keys(xc_interface *xch, char *keys);

[PATCH 4 of 5 v4] tools/ocaml: libxc bindings: Fix stub_xc_readconsolering()

[Andrew Cooper]

There are two problems with this function:
  * The caml_{enter,leave}_blocking_section() calls mean that two threads can
    compete for use of the static ring[] buffer.
  * It fails to retrieve the entire buffer if the hypervisor has used 32K or
    more of its console ring.

Rewrite the function using the new xc_consoleringsize() and
xc_readconsolering_buffer() functions to efficiently grab the entire console
ring.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

--
Changes since v3:
 * Use caml_alloc_string/memcpy in preference to caml_copy_string to allow
   for the possibility of NULL characters in the middle of the conring
Changes since v2:
 * Tweak style and remove redundant variables
Changes since v1:
 * Convert conring_size to being static to avoid needless hypercalls
 * Fix memory due to ordering of failwith_xc() and xc_hypercall_buffer_free()
 * Remove useless CAMLreturns()

diff -r c7b82dfbec34 -r 5bd08f35b362 tools/ocaml/libs/xc/xenctrl_stubs.c
--- a/tools/ocaml/libs/xc/xenctrl_stubs.c
+++ b/tools/ocaml/libs/xc/xenctrl_stubs.c
@@ -523,27 +523,47 @@ CAMLprim value stub_xc_evtchn_reset(valu
 	CAMLreturn(Val_unit);
 }
 
-
-#define RING_SIZE 32768
-static char ring[RING_SIZE];
-
 CAMLprim value stub_xc_readconsolering(value xch)
 {
-	unsigned int size = RING_SIZE - 1;
-	char *ring_ptr = ring;
+	static uint64_t conring_size = 0;
+	unsigned int nr_chars;
+	DECLARE_HYPERCALL_BUFFER(char, ring);
 	int retval;
 
 	CAMLparam1(xch);
+	CAMLlocal1(conring);
+
+	if (!conring_size)
+	{
+		if (xc_consoleringsize(_H(xch), &conring_size))
+			failwith_xc(_H(xch));
+
+		/* Round conring_size up to the next page, for NULL terminator
+		   and slop from a race with printk() in the hypervisor. */
+		conring_size = (conring_size + XC_PAGE_SIZE) & XC_PAGE_MASK;
+	}
+
+	nr_chars = conring_size - 1;
+	ring = xc_hypercall_buffer_alloc(_H(xch), ring, conring_size);
+
+	if (!ring)
+		caml_raise_out_of_memory();
 
 	caml_enter_blocking_section();
-	retval = xc_readconsolering(_H(xch), ring_ptr, &size, 0, 0, NULL);
+	retval = xc_readconsolering_buffer(_H(xch), HYPERCALL_BUFFER(ring),
+					   &nr_chars, 0, 0, NULL);
 	caml_leave_blocking_section();
 
 	if (retval)
+	{
+		xc_hypercall_buffer_free(_H(xch), ring);
 		failwith_xc(_H(xch));
+	}
 
-	ring[size] = '\0';
-	CAMLreturn(caml_copy_string(ring));
+	conring = caml_alloc_string(nr_chars);
+	memcpy(String_val(conring), ring, nr_chars);
+	xc_hypercall_buffer_free(_H(xch), ring);
+	CAMLreturn(conring);
 }
 
 CAMLprim value stub_xc_send_debug_keys(value xch, value keys)

[PATCH 5 of 5 v4] tools/ocaml: libxc bindings: Fix failwith_xc()

[Andrew Cooper]

The static error_str[] buffer is not thread-safe, and 1024 bytes is
unreasonably large.  Reduce to 256 bytes (which is still much larger than any
current use), and move it to being a stack variable.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Dave Scott <Dave.Scott@eu.citrix.com>

--
Changes since v1:
 * Mark as Noreturn, due to unconditional use of caml_raise_with_string()

diff -r 5bd08f35b362 -r e195c13431d5 tools/ocaml/libs/xc/xenctrl_stubs.c
--- a/tools/ocaml/libs/xc/xenctrl_stubs.c
+++ b/tools/ocaml/libs/xc/xenctrl_stubs.c
@@ -51,21 +51,22 @@
 	i1 = (uint32_t) Int64_val(Field(input, 0)); \
 	i2 = ((Field(input, 1) == Val_none) ? 0xffffffff : (uint32_t) Int64_val(Field(Field(input, 1), 0)));
 
-#define ERROR_STRLEN 1024
-void failwith_xc(xc_interface *xch)
+static void Noreturn failwith_xc(xc_interface *xch)
 {
-	static char error_str[ERROR_STRLEN];
+	char error_str[256];
 	if (xch) {
 		const xc_error *error = xc_get_last_error(xch);
 		if (error->code == XC_ERROR_NONE)
-                	snprintf(error_str, ERROR_STRLEN, "%d: %s", errno, strerror(errno));
+                	snprintf(error_str, sizeof(error_str),
+				 "%d: %s", errno, strerror(errno));
 		else
-			snprintf(error_str, ERROR_STRLEN, "%d: %s: %s",
-				 error->code,
+			snprintf(error_str, sizeof(error_str),
+				 "%d: %s: %s", error->code,
 				 xc_error_code_to_desc(error->code),
 				 error->message);
 	} else {
-		snprintf(error_str, ERROR_STRLEN, "Unable to open XC interface");
+		snprintf(error_str, sizeof(error_str),
+			 "Unable to open XC interface");
 	}
 	caml_raise_with_string(*caml_named_value("xc.error"), error_str);
 }

Re: [PATCH 4 of 5 v4] tools/ocaml: libxc bindings: Fix stub_xc_readconsolering()

[Dave Scott]

This looks good to me.

Acked-by: Dave Scott <dave.scott@eu.citrix.com>

> -----Original Message-----
> From: xen-devel-bounces@lists.xen.org [mailto:xen-devel-
> bounces@lists.xen.org] On Behalf Of Andrew Cooper
> Sent: 13 March 2013 12:52 PM
> To: xen-devel@lists.xen.org
> Cc: Ian Jackson; Keir (Xen.org); Ian Campbell; Jan Beulich; xen-
> api@lists.xen.org
> Subject: [Xen-devel] [PATCH 4 of 5 v4] tools/ocaml: libxc bindings: Fix
> stub_xc_readconsolering()
> 
> There are two problems with this function:
>   * The caml_{enter,leave}_blocking_section() calls mean that two threads
> can
>     compete for use of the static ring[] buffer.
>   * It fails to retrieve the entire buffer if the hypervisor has used 32K or
>     more of its console ring.
> 
> Rewrite the function using the new xc_consoleringsize() and
> xc_readconsolering_buffer() functions to efficiently grab the entire console
> ring.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> 
> --
> Changes since v3:
>  * Use caml_alloc_string/memcpy in preference to caml_copy_string to
> allow
>    for the possibility of NULL characters in the middle of the conring Changes
> since v2:
>  * Tweak style and remove redundant variables Changes since v1:
>  * Convert conring_size to being static to avoid needless hypercalls
>  * Fix memory due to ordering of failwith_xc() and
> xc_hypercall_buffer_free()
>  * Remove useless CAMLreturns()
> 
> diff -r c7b82dfbec34 -r 5bd08f35b362 tools/ocaml/libs/xc/xenctrl_stubs.c
> --- a/tools/ocaml/libs/xc/xenctrl_stubs.c
> +++ b/tools/ocaml/libs/xc/xenctrl_stubs.c
> @@ -523,27 +523,47 @@ CAMLprim value stub_xc_evtchn_reset(valu
>  	CAMLreturn(Val_unit);
>  }
> 
> -
> -#define RING_SIZE 32768
> -static char ring[RING_SIZE];
> -
>  CAMLprim value stub_xc_readconsolering(value xch)  {
> -	unsigned int size = RING_SIZE - 1;
> -	char *ring_ptr = ring;
> +	static uint64_t conring_size = 0;
> +	unsigned int nr_chars;
> +	DECLARE_HYPERCALL_BUFFER(char, ring);
>  	int retval;
> 
>  	CAMLparam1(xch);
> +	CAMLlocal1(conring);
> +
> +	if (!conring_size)
> +	{
> +		if (xc_consoleringsize(_H(xch), &conring_size))
> +			failwith_xc(_H(xch));
> +
> +		/* Round conring_size up to the next page, for NULL
> terminator
> +		   and slop from a race with printk() in the hypervisor. */
> +		conring_size = (conring_size + XC_PAGE_SIZE) &
> XC_PAGE_MASK;
> +	}
> +
> +	nr_chars = conring_size - 1;
> +	ring = xc_hypercall_buffer_alloc(_H(xch), ring, conring_size);
> +
> +	if (!ring)
> +		caml_raise_out_of_memory();
> 
>  	caml_enter_blocking_section();
> -	retval = xc_readconsolering(_H(xch), ring_ptr, &size, 0, 0, NULL);
> +	retval = xc_readconsolering_buffer(_H(xch),
> HYPERCALL_BUFFER(ring),
> +					   &nr_chars, 0, 0, NULL);
>  	caml_leave_blocking_section();
> 
>  	if (retval)
> +	{
> +		xc_hypercall_buffer_free(_H(xch), ring);
>  		failwith_xc(_H(xch));
> +	}
> 
> -	ring[size] = '\0';
> -	CAMLreturn(caml_copy_string(ring));
> +	conring = caml_alloc_string(nr_chars);
> +	memcpy(String_val(conring), ring, nr_chars);
> +	xc_hypercall_buffer_free(_H(xch), ring);
> +	CAMLreturn(conring);
>  }
> 
>  CAMLprim value stub_xc_send_debug_keys(value xch, value keys)
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel

Re: [PATCH 2 of 5 v4] tools/libxc: Helper function for XEN_SYSCTL_consoleringsize

[Andrew Cooper]

On 13/03/13 12:52, Andrew Cooper wrote:
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Keir/Jan: Ping? This is a hypervisor change.

>
> ---
> Changes since v2:
>  * Tweak style and errno in case of invalid pointer.
>
> diff -r 89f3c6846f6b -r 0bd32c19873e tools/libxc/xc_misc.c
> --- a/tools/libxc/xc_misc.c
> +++ b/tools/libxc/xc_misc.c
> @@ -100,6 +100,26 @@ int xc_readconsolering(xc_interface *xch
>      return ret;
>  }
>  
> +int xc_consoleringsize(xc_interface *xch, uint64_t *psize)
> +{
> +    int ret = -1;
> +    DECLARE_SYSCTL;
> +
> +    if ( !psize )
> +    {
> +        errno = EINVAL;
> +        return ret;
> +    }
> +
> +    sysctl.cmd = XEN_SYSCTL_consoleringsize;
> +    ret = do_sysctl(xch, &sysctl);
> +
> +    if ( !ret )
> +        *psize = sysctl.u.consoleringsize.size;
> +
> +    return ret;
> +}
> +
>  int xc_send_debug_keys(xc_interface *xch, char *keys)
>  {
>      int ret, len = strlen(keys);
> diff -r 89f3c6846f6b -r 0bd32c19873e tools/libxc/xenctrl.h
> --- a/tools/libxc/xenctrl.h
> +++ b/tools/libxc/xenctrl.h
> @@ -998,6 +998,7 @@ int xc_readconsolering(xc_interface *xch
>                         char *buffer,
>                         unsigned int *pnr_chars,
>                         int clear, int incremental, uint32_t *pindex);
> +int xc_consoleringsize(xc_interface *xch, uint64_t *psize);
>  
>  int xc_send_debug_keys(xc_interface *xch, char *keys);
>  
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel

Re: [PATCH 2 of 5 v4] tools/libxc: Helper function for XEN_SYSCTL_consoleringsize

[Andrew Cooper]

On 05/04/13 15:47, Andrew Cooper wrote:
> On 13/03/13 12:52, Andrew Cooper wrote:
>> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> Keir/Jan: Ping? This is a hypervisor change.

Apologies - this is actually a tools change. Ian/Ian?

>
>> ---
>> Changes since v2:
>>  * Tweak style and errno in case of invalid pointer.
>>
>> diff -r 89f3c6846f6b -r 0bd32c19873e tools/libxc/xc_misc.c
>> --- a/tools/libxc/xc_misc.c
>> +++ b/tools/libxc/xc_misc.c
>> @@ -100,6 +100,26 @@ int xc_readconsolering(xc_interface *xch
>>      return ret;
>>  }
>>  
>> +int xc_consoleringsize(xc_interface *xch, uint64_t *psize)
>> +{
>> +    int ret = -1;
>> +    DECLARE_SYSCTL;
>> +
>> +    if ( !psize )
>> +    {
>> +        errno = EINVAL;
>> +        return ret;
>> +    }
>> +
>> +    sysctl.cmd = XEN_SYSCTL_consoleringsize;
>> +    ret = do_sysctl(xch, &sysctl);
>> +
>> +    if ( !ret )
>> +        *psize = sysctl.u.consoleringsize.size;
>> +
>> +    return ret;
>> +}
>> +
>>  int xc_send_debug_keys(xc_interface *xch, char *keys)
>>  {
>>      int ret, len = strlen(keys);
>> diff -r 89f3c6846f6b -r 0bd32c19873e tools/libxc/xenctrl.h
>> --- a/tools/libxc/xenctrl.h
>> +++ b/tools/libxc/xenctrl.h
>> @@ -998,6 +998,7 @@ int xc_readconsolering(xc_interface *xch
>>                         char *buffer,
>>                         unsigned int *pnr_chars,
>>                         int clear, int incremental, uint32_t *pindex);
>> +int xc_consoleringsize(xc_interface *xch, uint64_t *psize);
>>  
>>  int xc_send_debug_keys(xc_interface *xch, char *keys);
>>  
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@lists.xen.org
>> http://lists.xen.org/xen-devel
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel

Re: [PATCH 2 of 5 v4] tools/libxc: Helper function for XEN_SYSCTL_consoleringsize

[Ian Campbell]

On Fri, 2013-04-05 at 15:50 +0100, Andrew Cooper wrote:
> On 05/04/13 15:47, Andrew Cooper wrote:
> > On 13/03/13 12:52, Andrew Cooper wrote:
> >> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> > Keir/Jan: Ping? This is a hypervisor change.
> 
> Apologies - this is actually a tools change. Ian/Ian?

Acked-by: Ian Campbell <ian.campbell@citrix.com>

Re: [PATCH 1 of 5 v4] common/sysctl: Introduce hypercall to query the console ring size

[Andrew Cooper]

On 13/03/13 12:52, Andrew Cooper wrote:
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Keir/Jan: Ping - this is a hypervisor change.

~Andrew

>
> --
> Changes since v2:
>  * Rebase on top of coverage patches.
>  * Reword hypercall comments.
>
> diff -r a6b81234b189 -r 89f3c6846f6b xen/common/sysctl.c
> --- a/xen/common/sysctl.c
> +++ b/xen/common/sysctl.c
> @@ -358,6 +358,10 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xe
>      }
>      break;
>  
> +    case XEN_SYSCTL_consoleringsize:
> +        ret = console_ring_size(&op->u.consoleringsize);
> +        break;
> +
>  #ifdef TEST_COVERAGE
>      case XEN_SYSCTL_coverage_op:
>          ret = sysctl_coverage_op(&op->u.coverage_op);
> diff -r a6b81234b189 -r 89f3c6846f6b xen/drivers/char/console.c
> --- a/xen/drivers/char/console.c
> +++ b/xen/drivers/char/console.c
> @@ -226,6 +226,12 @@ long read_console_ring(struct xen_sysctl
>      return 0;
>  }
>  
> +long console_ring_size(struct xen_sysctl_consoleringsize * op)
> +{
> +    op->size = conring_size;
> +    return 0;
> +}
> +
>  
>  /*
>   * *******************************************************
> diff -r a6b81234b189 -r 89f3c6846f6b xen/include/public/sysctl.h
> --- a/xen/include/public/sysctl.h
> +++ b/xen/include/public/sysctl.h
> @@ -632,6 +632,14 @@ typedef struct xen_sysctl_coverage_op xe
>  DEFINE_XEN_GUEST_HANDLE(xen_sysctl_coverage_op_t);
>  
>  
> +/* XEN_SYSCTL_consoleringsize */
> +/* Get the size of the hypervisor console ring in bytes. */
> +struct xen_sysctl_consoleringsize {
> +    uint64_t size; /* OUT */
> +};
> +typedef struct xen_sysctl_consoleringsize xen_sysctl_consoleringsize_t;
> +DEFINE_XEN_GUEST_HANDLE(xen_sysctl_consoleringsize_t);
> +
>  struct xen_sysctl {
>      uint32_t cmd;
>  #define XEN_SYSCTL_readconsole                    1
> @@ -653,6 +661,7 @@ struct xen_sysctl {
>  #define XEN_SYSCTL_cpupool_op                    18
>  #define XEN_SYSCTL_scheduler_op                  19
>  #define XEN_SYSCTL_coverage_op                   20
> +#define XEN_SYSCTL_consoleringsize               21
>      uint32_t interface_version; /* XEN_SYSCTL_INTERFACE_VERSION */
>      union {
>          struct xen_sysctl_readconsole       readconsole;
> @@ -674,6 +683,7 @@ struct xen_sysctl {
>          struct xen_sysctl_cpupool_op        cpupool_op;
>          struct xen_sysctl_scheduler_op      scheduler_op;
>          struct xen_sysctl_coverage_op       coverage_op;
> +        struct xen_sysctl_consoleringsize   consoleringsize;
>          uint8_t                             pad[128];
>      } u;
>  };
> diff -r a6b81234b189 -r 89f3c6846f6b xen/include/xen/console.h
> --- a/xen/include/xen/console.h
> +++ b/xen/include/xen/console.h
> @@ -12,6 +12,8 @@
>  
>  struct xen_sysctl_readconsole;
>  long read_console_ring(struct xen_sysctl_readconsole *op);
> +struct xen_sysctl_consoleringsize;
> +long console_ring_size(struct xen_sysctl_consoleringsize *op);
>  
>  void console_init_preirq(void);
>  void console_init_postirq(void);
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel

Re: [PATCH 1 of 5 v4] common/sysctl: Introduce hypercall to query the console ring size

[Ian Campbell]

On Fri, 2013-04-05 at 15:48 +0100, Andrew Cooper wrote:
> On 13/03/13 12:52, Andrew Cooper wrote:
> > Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> 
> Keir/Jan: Ping - this is a hypervisor change.

Anyone? This hypervisor side portion of this series seems pretty trivial
to me.

Ian.

Re: [PATCH 3 of 5 v4] tools/libxc: Implement xc_readconsolering_buffer()

[Ian Campbell]

On Wed, 2013-03-13 at 12:52 +0000, Andrew Cooper wrote:
> +/*
> + * For both readconsolering functions, *pnr_chars is both an input and
> + * output.  As an input, it specifies the size of *buffer, and as an output
> + * indicates now many character Xen wrote into *buffer.
> + *
> + * The 'clear' parameter indicates whether Xen should clear the buffer or not.

Buffer here refers to Xen's internal ring, not the char *buffer argument
to this function, right? If so the wording (at least in the context) is
a bit confusing!

The actual code looks good to me.

Ian.