From: Jan Beulich <jbeulich@suse.com>
Date: Wed, 7 Dec 2016 12:50:22 +0000 (+0100)
Subject: x86: make more use of wr{f,g}sbase()
X-Git-Tag: archive/raspbian/4.11.1-1+rpi1~1^2~66^2~3260
X-Git-Url: https://dgit.raspbian.org/%22http:/www.example.com/cgi/%22https:/%22bookmarks:/%22man:///%22http:/www.example.com/cgi/%22https:/%22bookmarks:/%22man:/?a=commitdiff_plain;h=b053c185e3ff58628233bf90742c1ffd9a3189ed;p=xen.git

x86: make more use of wr{f,g}sbase()

With suitable canonical address checks added these can also be used in
do_set_segment_base().

Also with a canonical address check now in place, there's no need for
priv_op_write_msr() to use wrmsr_safe() anymore.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
---

diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index d8b68e1113..e03753bff1 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -2613,9 +2613,9 @@ static int priv_op_write_msr(unsigned int reg, uint64_t val,
         return X86EMUL_OKAY;
 
     case MSR_SHADOW_GS_BASE:
-        if ( is_pv_32bit_domain(currd) || !is_canonical_address(val) ||
-             wrmsr_safe(MSR_SHADOW_GS_BASE, val) )
+        if ( is_pv_32bit_domain(currd) || !is_canonical_address(val) )
             break;
+        wrmsrl(MSR_SHADOW_GS_BASE, val);
         curr->arch.pv_vcpu.gs_base_user = val;
         return X86EMUL_OKAY;
 
diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
index b8b6b70a06..9ead02e181 100644
--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -1037,24 +1037,33 @@ long do_set_segment_base(unsigned int which, unsigned long base)
     switch ( which )
     {
     case SEGBASE_FS:
-        if ( wrmsr_safe(MSR_FS_BASE, base) )
-            ret = -EFAULT;
-        else
+        if ( is_canonical_address(base) )
+        {
+            wrfsbase(base);
             v->arch.pv_vcpu.fs_base = base;
+        }
+        else
+            ret = -EINVAL;
         break;
 
     case SEGBASE_GS_USER:
-        if ( wrmsr_safe(MSR_SHADOW_GS_BASE, base) )
-            ret = -EFAULT;
-        else
+        if ( is_canonical_address(base) )
+        {
+            wrmsrl(MSR_SHADOW_GS_BASE, base);
             v->arch.pv_vcpu.gs_base_user = base;
+        }
+        else
+            ret = -EINVAL;
         break;
 
     case SEGBASE_GS_KERNEL:
-        if ( wrmsr_safe(MSR_GS_BASE, base) )
-            ret = -EFAULT;
-        else
+        if ( is_canonical_address(base) )
+        {
+            wrgsbase(base);
             v->arch.pv_vcpu.gs_base_kernel = base;
+        }
+        else
+            ret = -EINVAL;
         break;
 
     case SEGBASE_GS_USER_SEL: