Re: [Xen-devel] [PATCH for-next 2/3] x86/pv: Use DIV_ROUND_UP() when converting between GDT entries and frames

[Jan Beulich]

>>> On 19.10.17 at 17:47,  wrote:
> Also consistently use use nr_frames, rather than mixing nr_pages with a
> frames[] array.
> 
> No functional change.
> 
> Signed-off-by: Andrew Cooper 

Reviewed-by: Jan Beulich 



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[Xen-devel] [PATCH for-next 2/3] x86/pv: Use DIV_ROUND_UP() when converting between GDT entries and frames

[Andrew Cooper]

Also consistently use use nr_frames, rather than mixing nr_pages with a
frames[] array.

No functional change.

Signed-off-by: Andrew Cooper 
---
CC: Jan Beulich 
CC: Wei Liu 
---
 xen/arch/x86/domain.c   |  8 +---
 xen/arch/x86/pv/descriptor-tables.c | 17 -
 2 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index c28ac38..98bfb35 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -1017,12 +1017,14 @@ int arch_set_info_guest(
 else
 {
 unsigned long gdt_frames[ARRAY_SIZE(v->arch.pv_vcpu.gdt_frames)];
-unsigned int n = (c.cmp->gdt_ents + 511) / 512;
+unsigned int nr_frames = DIV_ROUND_UP(c.cmp->gdt_ents, 512);
 
-if ( n > ARRAY_SIZE(v->arch.pv_vcpu.gdt_frames) )
+if ( nr_frames > ARRAY_SIZE(v->arch.pv_vcpu.gdt_frames) )
 return -EINVAL;
-for ( i = 0; i < n; ++i )
+
+for ( i = 0; i < nr_frames; ++i )
 gdt_frames[i] = c.cmp->gdt_frames[i];
+
 rc = (int)pv_set_gdt(v, gdt_frames, c.cmp->gdt_ents);
 }
 if ( rc != 0 )
diff --git a/xen/arch/x86/pv/descriptor-tables.c 
b/xen/arch/x86/pv/descriptor-tables.c
index 9c8de1d..e31c97e 100644
--- a/xen/arch/x86/pv/descriptor-tables.c
+++ b/xen/arch/x86/pv/descriptor-tables.c
@@ -57,14 +57,13 @@ long pv_set_gdt(struct vcpu *v, unsigned long *frames, 
unsigned int entries)
 {
 struct domain *d = v->domain;
 l1_pgentry_t *pl1e;
-/* NB. There are 512 8-byte entries per GDT page. */
-unsigned int i, nr_pages = (entries + 511) / 512;
+unsigned int i, nr_frames = DIV_ROUND_UP(entries, 512);
 
 if ( entries > FIRST_RESERVED_GDT_ENTRY )
 return -EINVAL;
 
 /* Check the pages in the new GDT. */
-for ( i = 0; i < nr_pages; i++ )
+for ( i = 0; i < nr_frames; i++ )
 {
 struct page_info *page;
 
@@ -85,7 +84,7 @@ long pv_set_gdt(struct vcpu *v, unsigned long *frames, 
unsigned int entries)
 /* Install the new GDT. */
 v->arch.pv_vcpu.gdt_ents = entries;
 pl1e = pv_gdt_ptes(v);
-for ( i = 0; i < nr_pages; i++ )
+for ( i = 0; i < nr_frames; i++ )
 {
 v->arch.pv_vcpu.gdt_frames[i] = frames[i];
 l1e_write([i], l1e_from_pfn(frames[i], __PAGE_HYPERVISOR_RW));
@@ -104,7 +103,7 @@ long pv_set_gdt(struct vcpu *v, unsigned long *frames, 
unsigned int entries)
 long do_set_gdt(XEN_GUEST_HANDLE_PARAM(xen_ulong_t) frame_list,
 unsigned int entries)
 {
-int nr_pages = (entries + 511) / 512;
+unsigned int nr_frames = DIV_ROUND_UP(entries, 512);
 unsigned long frames[16];
 struct vcpu *curr = current;
 long ret;
@@ -113,7 +112,7 @@ long do_set_gdt(XEN_GUEST_HANDLE_PARAM(xen_ulong_t) 
frame_list,
 if ( entries > FIRST_RESERVED_GDT_ENTRY )
 return -EINVAL;
 
-if ( copy_from_guest(frames, frame_list, nr_pages) )
+if ( copy_from_guest(frames, frame_list, nr_frames) )
 return -EFAULT;
 
 domain_lock(curr->domain);
@@ -130,7 +129,7 @@ int compat_set_gdt(XEN_GUEST_HANDLE_PARAM(uint) frame_list,
unsigned int entries)
 {
 struct vcpu *curr = current;
-unsigned int i, nr_pages = (entries + 511) / 512;
+unsigned int i, nr_frames = DIV_ROUND_UP(entries, 512);
 unsigned long frames[16];
 int ret;
 
@@ -138,10 +137,10 @@ int compat_set_gdt(XEN_GUEST_HANDLE_PARAM(uint) 
frame_list,
 if ( entries > FIRST_RESERVED_GDT_ENTRY )
 return -EINVAL;
 
-if ( !guest_handle_okay(frame_list, nr_pages) )
+if ( !guest_handle_okay(frame_list, nr_frames) )
 return -EFAULT;
 
-for ( i = 0; i < nr_pages; ++i )
+for ( i = 0; i < nr_frames; ++i )
 {
 unsigned int frame;
 
-- 
2.1.4


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