Re: [Xen-devel] [PATCH 38/60] x86: make loading of GDT at context switch more modular

Re: [Xen-devel] [PATCH 38/60] x86: make loading of GDT at context switch more modular

[Jan Beulich]

>>> On 28.05.19 at 12:32, <jgross@suse.com> wrote:
> In preparation for core scheduling carve out the GDT related
> functionality (writing GDT related PTEs, loading default of full GDT)
> into sub-functions.
> 
> Signed-off-by: Juergen Gross <jgross@suse.com>
> Acked-by: Jan Beulich <jbeulich@suse.com>
> ---
> RFC V2: split off non-refactoring part
> V1: constify pointers, use initializers (Jan Beulich)

I'm getting the impression that this and the following patch are
independent of the earlier parts of the series, and hence could
in principle go in right away? Am I overlooking anything?

Andrew, objections?

Jan
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Re: [Xen-devel] [PATCH 38/60] x86: make loading of GDT at context switch more modular

[Juergen Gross]

On 02.07.19 14:48, Jan Beulich wrote:
>>>> On 28.05.19 at 12:32, <jgross@suse.com> wrote:
>> In preparation for core scheduling carve out the GDT related
>> functionality (writing GDT related PTEs, loading default of full GDT)
>> into sub-functions.
>>
>> Signed-off-by: Juergen Gross <jgross@suse.com>
>> Acked-by: Jan Beulich <jbeulich@suse.com>
>> ---
>> RFC V2: split off non-refactoring part
>> V1: constify pointers, use initializers (Jan Beulich)
> 
> I'm getting the impression that this and the following patch are
> independent of the earlier parts of the series, and hence could
> in principle go in right away? Am I overlooking anything?

No, should work. Patches apply and the result shows no compiling errors.


Juergen

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Re: [Xen-devel] [PATCH 38/60] x86: make loading of GDT at context switch more modular

[Andrew Cooper]

Subject "load of the GDT"

On 28/05/2019 11:32, Juergen Gross wrote:
> In preparation for core scheduling carve out the GDT related

"for core scheduling, carve"

> functionality (writing GDT related PTEs, loading default of full GDT)
> into sub-functions.
>
> Signed-off-by: Juergen Gross <jgross@suse.com>
> Acked-by: Jan Beulich <jbeulich@suse.com>
> ---
> RFC V2: split off non-refactoring part
> V1: constify pointers, use initializers (Jan Beulich)
> ---
>  xen/arch/x86/domain.c | 57 +++++++++++++++++++++++++++++++--------------------
>  1 file changed, 35 insertions(+), 22 deletions(-)
>
> diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
> index d3ee699da6..adc06154ee 100644
> --- a/xen/arch/x86/domain.c
> +++ b/xen/arch/x86/domain.c
> @@ -1626,6 +1626,37 @@ static inline bool need_full_gdt(const struct domain *d)
>      return is_pv_domain(d) && !is_idle_domain(d);
>  }
>  
> +static inline void write_full_gdt_ptes(seg_desc_t *gdt, const struct vcpu *v)

We typically don't use inline for local static functions.

All can be fixed on commit.  Acked-by: Andrew Cooper
<andrew.cooper3@citrix.com>

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[Xen-devel] [PATCH 38/60] x86: make loading of GDT at context switch more modular

[Juergen Gross]

In preparation for core scheduling carve out the GDT related
functionality (writing GDT related PTEs, loading default of full GDT)
into sub-functions.

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
---
RFC V2: split off non-refactoring part
V1: constify pointers, use initializers (Jan Beulich)
---
 xen/arch/x86/domain.c | 57 +++++++++++++++++++++++++++++++--------------------
 1 file changed, 35 insertions(+), 22 deletions(-)

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index d3ee699da6..adc06154ee 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -1626,6 +1626,37 @@ static inline bool need_full_gdt(const struct domain *d)
     return is_pv_domain(d) && !is_idle_domain(d);
 }
 
+static inline void write_full_gdt_ptes(seg_desc_t *gdt, const struct vcpu *v)
+{
+    unsigned long mfn = virt_to_mfn(gdt);
+    l1_pgentry_t *pl1e = pv_gdt_ptes(v);
+    unsigned int i;
+
+    for ( i = 0; i < NR_RESERVED_GDT_PAGES; i++ )
+        l1e_write(pl1e + FIRST_RESERVED_GDT_PAGE + i,
+                  l1e_from_pfn(mfn + i, __PAGE_HYPERVISOR_RW));
+}
+
+static inline void load_full_gdt(const struct vcpu *v, unsigned int cpu)
+{
+    struct desc_ptr gdt_desc = {
+        .limit = LAST_RESERVED_GDT_BYTE,
+        .base = GDT_VIRT_START(v),
+    };
+
+    lgdt(&gdt_desc);
+}
+
+static inline void load_default_gdt(const seg_desc_t *gdt, unsigned int cpu)
+{
+    struct desc_ptr gdt_desc = {
+        .limit = LAST_RESERVED_GDT_BYTE,
+        .base  = (unsigned long)(gdt - FIRST_RESERVED_GDT_ENTRY),
+    };
+
+    lgdt(&gdt_desc);
+}
+
 static void __context_switch(void)
 {
     struct cpu_user_regs *stack_regs = guest_cpu_user_regs();
@@ -1634,7 +1665,6 @@ static void __context_switch(void)
     struct vcpu          *n = current;
     struct domain        *pd = p->domain, *nd = n->domain;
     seg_desc_t           *gdt;
-    struct desc_ptr       gdt_desc;
 
     ASSERT(p != n);
     ASSERT(!vcpu_cpu_dirty(n));
@@ -1676,25 +1706,13 @@ static void __context_switch(void)
 
     gdt = !is_pv_32bit_domain(nd) ? per_cpu(gdt_table, cpu) :
                                     per_cpu(compat_gdt_table, cpu);
-    if ( need_full_gdt(nd) )
-    {
-        unsigned long mfn = virt_to_mfn(gdt);
-        l1_pgentry_t *pl1e = pv_gdt_ptes(n);
-        unsigned int i;
 
-        for ( i = 0; i < NR_RESERVED_GDT_PAGES; i++ )
-            l1e_write(pl1e + FIRST_RESERVED_GDT_PAGE + i,
-                      l1e_from_pfn(mfn + i, __PAGE_HYPERVISOR_RW));
-    }
+    if ( need_full_gdt(nd) )
+        write_full_gdt_ptes(gdt, n);
 
     if ( need_full_gdt(pd) &&
          ((p->vcpu_id != n->vcpu_id) || !need_full_gdt(nd)) )
-    {
-        gdt_desc.limit = LAST_RESERVED_GDT_BYTE;
-        gdt_desc.base  = (unsigned long)(gdt - FIRST_RESERVED_GDT_ENTRY);
-
-        lgdt(&gdt_desc);
-    }
+        load_default_gdt(gdt, cpu);
 
     write_ptbase(n);
 
@@ -1707,12 +1725,7 @@ static void __context_switch(void)
 
     if ( need_full_gdt(nd) &&
          ((p->vcpu_id != n->vcpu_id) || !need_full_gdt(pd)) )
-    {
-        gdt_desc.limit = LAST_RESERVED_GDT_BYTE;
-        gdt_desc.base = GDT_VIRT_START(n);
-
-        lgdt(&gdt_desc);
-    }
+        load_full_gdt(n, cpu);
 
     if ( pd != nd )
         cpumask_clear_cpu(cpu, pd->dirty_cpumask);
-- 
2.16.4


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