[PATCH v3 2/2] x86/amd: Enable TCE in Xen

["Teddy Astie" <teddy.astie@xxxxxxxxxx>]

Aside exposing this flag to guests, Xen can also make use of it
to reduce the cost of some TLB flushes. Enable this flag if supported
by hardware.

Signed-off-by: Teddy Astie <teddy.astie@xxxxxxxxxx>
---
v2:
 - Add changelog entry
 - use trampoline_efer
 - use cpu_has_tce instead of opencoded boot_cpu_has(X86_FEATURE_TCE)
v3:
 - drop message
 - use bootsym for modifying trampoline_efer
---
 CHANGELOG.md                          | 2 +-
 xen/arch/x86/include/asm/cpufeature.h | 1 +
 xen/arch/x86/setup.c                  | 6 ++++++
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index dbfecefbd4..375905e68a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,7 +18,7 @@ The format is based on [Keep a 
Changelog](https://keepachangelog.com/en/1.0.0/)
    - Support PCI passthrough for HVM domUs when dom0 is PVH (note SR-IOV
      capability usage is not yet supported on PVH dom0).
    - Smoke tests for the FreeBSD Xen builds in Cirrus CI.
-   - Guest support for AMD Translation Cache Extension feature.
+   - Guest and Xen support for AMD Translation Cache Extension feature.
 
 ### Removed
 
diff --git a/xen/arch/x86/include/asm/cpufeature.h 
b/xen/arch/x86/include/asm/cpufeature.h
index 05399fb9c9..ab6d07b767 100644
--- a/xen/arch/x86/include/asm/cpufeature.h
+++ b/xen/arch/x86/include/asm/cpufeature.h
@@ -114,6 +114,7 @@ static inline bool boot_cpu_has(unsigned int feat)
 #define cpu_has_xop             boot_cpu_has(X86_FEATURE_XOP)
 #define cpu_has_skinit          boot_cpu_has(X86_FEATURE_SKINIT)
 #define cpu_has_fma4            boot_cpu_has(X86_FEATURE_FMA4)
+#define cpu_has_tce             boot_cpu_has(X86_FEATURE_TCE)
 #define cpu_has_tbm             boot_cpu_has(X86_FEATURE_TBM)
 
 /* CPUID level 0x0000000D:1.eax */
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index d70abb7e0c..9b1924ad05 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -2008,6 +2008,12 @@ void asmlinkage __init noreturn __start_xen(void)
     if ( cpu_has_pku )
         set_in_cr4(X86_CR4_PKE);
 
+    if ( cpu_has_tce )
+    {
+        write_efer(read_efer() | EFER_TCE);
+        bootsym(trampoline_efer) |= EFER_TCE;
+    }
+
     if ( opt_invpcid && cpu_has_invpcid )
         use_invpcid = true;
 
-- 
2.47.2



Teddy Astie | Vates XCP-ng Developer

XCP-ng & Xen Orchestra - Vates solutions

web: https://vates.tech