| Message ID | 20210422151007.2205-2-jgross@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | xen: remove some checks for always present Xen features | expand |
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 <jgross@suse.com> > --- > 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 <jgross@suse.com> >> --- >> 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
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); + } }
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 <jgross@suse.com> --- drivers/xen/features.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)