AMD Zen3 adds the NullSelectorClearsBase bit to indicate that loading
a NULL segment selector zeroes the base and limit fields, as well as
just attributes.
Expose bit to all guests.
Suggested-by: Andrew Cooper <andrew.coop...@citrix.com>
Signed-off-by: Jane Malalane <jane.malal...@citrix.com>
---
CC: Wei Liu <w...@xen.org>
CC: Jan Beulich <jbeul...@suse.com>
CC: Andrew Cooper <andrew.coop...@citrix.com>
CC: "Roger Pau Monné" <roger....@citrix.com>
CC: Pu Wen <pu...@hygon.cn>
CC: Andy Lutomirski <l...@kernel.org>
---
tools/libs/light/libxl_cpuid.c | 1 +
tools/misc/xen-cpuid.c | 1 +
xen/include/public/arch-x86/cpufeatureset.h | 1 +
3 files changed, 3 insertions(+)
diff --git a/tools/libs/light/libxl_cpuid.c b/tools/libs/light/libxl_cpuid.c
index b2c673841a..d667c36f31 100644
--- a/tools/libs/light/libxl_cpuid.c
+++ b/tools/libs/light/libxl_cpuid.c
@@ -289,6 +289,7 @@ int libxl_cpuid_parse_config(libxl_cpuid_policy_list
*cpuid, const char* str)
{"svm_pausefilt",0x8000000a, NA, CPUID_REG_EDX, 10, 1},
{"lfence+", 0x80000021, NA, CPUID_REG_EAX, 2, 1},
+ {"nscb", 0x80000021, NA, CPUID_REG_EAX, 6, 1},
{"maxhvleaf", 0x40000000, NA, CPUID_REG_EAX, 0, 8},
diff --git a/tools/misc/xen-cpuid.c b/tools/misc/xen-cpuid.c
index 735bcf8f0e..d79e67ecfb 100644
--- a/tools/misc/xen-cpuid.c
+++ b/tools/misc/xen-cpuid.c
@@ -185,6 +185,7 @@ static const char *const str_7a1[32] =
static const char *const str_e21a[32] =
{
[ 2] = "lfence+",
+ [ 6] = "nscb",
};
static const struct {
diff --git a/xen/include/public/arch-x86/cpufeatureset.h
b/xen/include/public/arch-x86/cpufeatureset.h
index 380b51b1b3..e5a7c94c78 100644
--- a/xen/include/public/arch-x86/cpufeatureset.h
+++ b/xen/include/public/arch-x86/cpufeatureset.h
@@ -285,6 +285,7 @@ XEN_CPUFEATURE(FSRCS, 10*32+12) /*A Fast Short REP
CMPSB/SCASB */
/* AMD-defined CPU features, CPUID level 0x80000021.eax, word 11 */
XEN_CPUFEATURE(LFENCE_DISPATCH, 11*32+ 2) /*A LFENCE always serializing */
+XEN_CPUFEATURE(NSCB, 11*32+ 6) /*A Null Selector Clears Base */
#endif /* XEN_CPUFEATURE */
--
2.11.0
