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Re: [Xen-devel] [PATCH 2/2] x86/HVM: Use fixed TSC value when saving or restoring domain

On 03/31/2014 05:51 AM, Jan Beulich wrote:

--- a/xen/arch/x86/hvm/save.c
+++ b/xen/arch/x86/hvm/save.c
@@ -24,7 +24,7 @@
  #include <asm/hvm/support.h>
  #include <public/hvm/save.h>
-void arch_hvm_save(struct domain *d, struct hvm_save_header *hdr)
+void arch_hvm_save(struct domain *dom, struct hvm_save_header *hdr)
The change is unmotivated (afaict) and inconsistent with most other
code - we conventionally use "d" for struct domain * variables. Please
drop the change here and use "d" throughout the rest of the patch,
at once resulting in less churn and hence making it easier to review.

The reason for this change is subsequent

which will not work as

The alternatives as I see are
* Declare a temporary variable for use with rdtscll
* Change rdtscll's definition to use something else instead of variable 'd'. Say, eax and edx (hopefully this won't clash with something else)

index 95b4b91..032eb23 100644
--- a/xen/include/xen/time.h
+++ b/xen/include/xen/time.h
@@ -32,7 +32,8 @@ struct vcpu;
  typedef s64 s_time_t;
  #define PRI_stime PRId64
-s_time_t get_s_time(void);
+s_time_t get_s_time_fixed(u64 at_tick);
+#define get_s_time() get_s_time_fixed(0)
get_s_time(), through NOW(), has quite many users, so I'm not certain
the code bloat resulting from this is desirable. I'd suggest the function
to remain such; the compiler will be able to make it a mov+jmp.

Sorry, not sure I understand what you are asking for.

There shouldn't be much of code size increase since get_s_time() currently (and get_s_time_fixed() after this patch is applied) are not inlines. The only increase is due to routine itself getting very slightly larger.

But I suspect you meant something else.


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