Re: x86: Declarations for compat_set_{cx,px}_pminfo()

[Nicola Vetrini <nicola.vetrini@bugseng.com>]

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On 2024-11-18 22:41, Andrew Cooper wrote:
> Hello,
> 
> Eclair reports Rule 8.4 violations for these two.  They're real
> violations, but fixing them is proving challenging.
> 
> Because of how x86_64/platform_hypercall.c sets up some defines and
> includes ../platform_hypercall.c, the declarations of
> compat_set_{cx,px}_pminfo() of pmstat.h become compat ones.
> 
> Therefore the real hypercall handler does see a correct declaration.
> 
> However, the implementation in cpufreq.c does not get the compat-ified
> version of pmstat.h, so misses the declaration and thus the violation.
> 
> Worse however is the fact that cpufreq.c depends on not having the:
> 
> #define xen_processor_performance compat_processor_performance
> 
> in scope while it's transforming between the two formats, meaning we
> can't simply reuse pmstat.h with suitable defines.
> 
> Any clever ideas for how to untangle this mess, before I go for the
> brute force approach of an #if COMPAT section in the main hypercall 
> handler?
> 

Yeah, that is why these were among the last ones. I'm afraid I didn't 
come up with a reasonable to deal with this either.

You can find attached a tentative patch I made (not build tested, and 
also based on an older tree). A last resort may be to special-case those 
declarations, but that's undesirable.

-- 
Nicola Vetrini, BSc
Software Engineer, BUGSENG srl (https://bugseng.com)

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commit caffa89a06275b6b50ace99170b99b500b7b32f7
Author: Nicola Vetrini <nicola.vetrini@bugseng.com>
Date:   Wed Nov 29 12:23:25 2023 +0100

    x86_64/platform_hypercall: provide proper declarations for compat_*
    
    Signed-off-by: Nicola Vetrini <nicola.vetrini@bugseng.com>

diff --git a/xen/arch/x86/x86_64/platform_hypercall.c b/xen/arch/x86/x86_64/platform_hypercall.c
index 347f5d65330e..3ad15742d9ef 100644
--- a/xen/arch/x86/x86_64/platform_hypercall.c
+++ b/xen/arch/x86/x86_64/platform_hypercall.c
@@ -5,6 +5,7 @@
 EMIT_FILE;
 
 #include <xen/lib.h>
+#include <xen/pmstat.h>
 #include <xen/hypercall.h>
 
 #define xen_platform_op     compat_platform_op
@@ -14,11 +15,13 @@ EMIT_FILE;
 #define efi_get_info        efi_compat_get_info
 #define efi_runtime_call(x) efi_compat_runtime_call(x)
 
-#define xen_processor_performance compat_processor_performance
-#define set_px_pminfo       compat_set_px_pminfo
+#define xen_processor_performance compat_xen_processor_performance
+int compat_set_px_pminfo(uint32_t acpi_id, 
+                         struct compat_xen_processor_performance *perf);
 
-#define xen_processor_power compat_processor_power
-#define set_cx_pminfo       compat_set_cx_pminfo
+#define xen_processor_power       compat_xen_processor_power
+long compat_set_cx_pminfo(uint32_t acpi_id,
+                          struct compat_xen_processor_power *power);
 
 #define xen_pf_pcpuinfo xenpf_pcpuinfo
 CHECK_pf_pcpuinfo;