Linux kernel is not supported to run on Xen versions older than 4.0.
Add tests for required Xen features always being present in Xen 4.0
and newer.
Signed-off-by: Juergen Gross <[email protected]>
---
drivers/xen/features.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/drivers/xen/features.c b/drivers/xen/features.c
index 25c053b09605..60503299c9bc 100644
--- a/drivers/xen/features.c
+++ b/drivers/xen/features.c
@@ -9,13 +9,26 @@
#include <linux/types.h>
#include <linux/cache.h>
#include <linux/export.h>
+#include <linux/printk.h>
#include <asm/xen/hypercall.h>
+#include <xen/xen.h>
#include <xen/interface/xen.h>
#include <xen/interface/version.h>
#include <xen/features.h>
+/*
+ * Linux kernel expects at least Xen 4.0.
+ *
+ * Assume some features to be available for that reason (depending on guest
+ * mode, of course).
+ */
+#define chk_feature(f) { \
+ if (!xen_feature(f)) \
+ pr_err("Xen: feature %s not available!\n", #f); \
+ }
+
u8 xen_features[XENFEAT_NR_SUBMAPS * 32] __read_mostly;
EXPORT_SYMBOL_GPL(xen_features);
@@ -31,4 +44,9 @@ void xen_setup_features(void)
for (j = 0; j < 32; j++)
xen_features[i * 32 + j] = !!(fi.submap & 1<<j);
}
+
+ if (xen_pv_domain()) {
+ chk_feature(XENFEAT_mmu_pt_update_preserve_ad);
+ chk_feature(XENFEAT_gnttab_map_avail_bits);
+ }
}
--
2.26.2
On Thu, 22 Apr 2021, Juergen Gross wrote:
> Linux kernel is not supported to run on Xen versions older than 4.0.
>
> Add tests for required Xen features always being present in Xen 4.0
> and newer.
>
> Signed-off-by: Juergen Gross <[email protected]>
> ---
> drivers/xen/features.c | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
> diff --git a/drivers/xen/features.c b/drivers/xen/features.c
> index 25c053b09605..60503299c9bc 100644
> --- a/drivers/xen/features.c
> +++ b/drivers/xen/features.c
> @@ -9,13 +9,26 @@
> #include <linux/types.h>
> #include <linux/cache.h>
> #include <linux/export.h>
> +#include <linux/printk.h>
>
> #include <asm/xen/hypercall.h>
>
> +#include <xen/xen.h>
> #include <xen/interface/xen.h>
> #include <xen/interface/version.h>
> #include <xen/features.h>
>
> +/*
> + * Linux kernel expects at least Xen 4.0.
> + *
> + * Assume some features to be available for that reason (depending on guest
> + * mode, of course).
> + */
> +#define chk_feature(f) { \
> + if (!xen_feature(f)) \
> + pr_err("Xen: feature %s not available!\n", #f); \
> + }
I think this could be done as a static inline function in
include/xen/features.h. That way it would be available everywhere. Also,
static inlines are better than macro when it is possible to use them in
terms of code safety.
> u8 xen_features[XENFEAT_NR_SUBMAPS * 32] __read_mostly;
> EXPORT_SYMBOL_GPL(xen_features);
>
> @@ -31,4 +44,9 @@ void xen_setup_features(void)
> for (j = 0; j < 32; j++)
> xen_features[i * 32 + j] = !!(fi.submap & 1<<j);
> }
> +
> + if (xen_pv_domain()) {
> + chk_feature(XENFEAT_mmu_pt_update_preserve_ad);
> + chk_feature(XENFEAT_gnttab_map_avail_bits);
> + }
> }
> --
> 2.26.2
>
On 22.04.21 17:26, Stefano Stabellini wrote:
> On Thu, 22 Apr 2021, Juergen Gross wrote:
>> Linux kernel is not supported to run on Xen versions older than 4.0.
>>
>> Add tests for required Xen features always being present in Xen 4.0
>> and newer.
>>
>> Signed-off-by: Juergen Gross <[email protected]>
>> ---
>> drivers/xen/features.c | 18 ++++++++++++++++++
>> 1 file changed, 18 insertions(+)
>>
>> diff --git a/drivers/xen/features.c b/drivers/xen/features.c
>> index 25c053b09605..60503299c9bc 100644
>> --- a/drivers/xen/features.c
>> +++ b/drivers/xen/features.c
>> @@ -9,13 +9,26 @@
>> #include <linux/types.h>
>> #include <linux/cache.h>
>> #include <linux/export.h>
>> +#include <linux/printk.h>
>>
>> #include <asm/xen/hypercall.h>
>>
>> +#include <xen/xen.h>
>> #include <xen/interface/xen.h>
>> #include <xen/interface/version.h>
>> #include <xen/features.h>
>>
>> +/*
>> + * Linux kernel expects at least Xen 4.0.
>> + *
>> + * Assume some features to be available for that reason (depending on guest
>> + * mode, of course).
>> + */
>> +#define chk_feature(f) { \
>> + if (!xen_feature(f)) \
>> + pr_err("Xen: feature %s not available!\n", #f); \
>> + }
>
> I think this could be done as a static inline function in
> include/xen/features.h. That way it would be available everywhere. Also,
> static inlines are better than macro when it is possible to use them in
> terms of code safety.
It is a macro in order to have only one parameter.
And being a local macro is rendering the code safety reasoning moot.
Additionally I don't want this testing to be scattered all over the
code base. It should be done in one place only.
Juergen
On 4/22/21 11:10 AM, Juergen Gross wrote:
>
> +/*
> + * Linux kernel expects at least Xen 4.0.
> + *
> + * Assume some features to be available for that reason (depending on guest
> + * mode, of course).
> + */
> +#define chk_feature(f) { \
> + if (!xen_feature(f)) \
> + pr_err("Xen: feature %s not available!\n", #f); \
> + }
With your changes in the subsequent patches, are we still going to function properly without those features? (i.e. maybe we should just panic)
(Also, chk_required_features() perhaps?)
-boris
> +
> u8 xen_features[XENFEAT_NR_SUBMAPS * 32] __read_mostly;
> EXPORT_SYMBOL_GPL(xen_features);
>
> @@ -31,4 +44,9 @@ void xen_setup_features(void)
> for (j = 0; j < 32; j++)
> xen_features[i * 32 + j] = !!(fi.submap & 1<<j);
> }
> +
> + if (xen_pv_domain()) {
> + chk_feature(XENFEAT_mmu_pt_update_preserve_ad);
> + chk_feature(XENFEAT_gnttab_map_avail_bits);
> + }
> }
On 10.05.21 14:11, Boris Ostrovsky wrote:
>
> On 4/22/21 11:10 AM, Juergen Gross wrote:
>>
>> +/*
>> + * Linux kernel expects at least Xen 4.0.
>> + *
>> + * Assume some features to be available for that reason (depending on guest
>> + * mode, of course).
>> + */
>> +#define chk_feature(f) { \
>> + if (!xen_feature(f)) \
>> + pr_err("Xen: feature %s not available!\n", #f); \
>> + }
>
>
> With your changes in the subsequent patches, are we still going to function properly without those features? (i.e. maybe we should just panic)
Depends on the use case.
XENFEAT_gnttab_map_avail_bits is relevant for driver domains using
user space backends only. In case it is not available "interesting"
things might happen.
XENFEAT_mmu_pt_update_preserve_ad not being present would result in
a subsequent mmu-update function using that feature returning -ENOSYS,
so this wouldn't be unrecognized.
So panic() might be a good idea in case the features are not available.
> (Also, chk_required_features() perhaps?)
Fine with me.
Juergen