Mailing List Archive

commit 0f640366e5f8fa43ed464c56d00ef960824c9611
Author: Roger Pau Monné <roger.pau@citrix.com>
AuthorDate: Tue Jan 30 10:14:00 2024 +0100
Commit: Andrew Cooper <andrew.cooper3@citrix.com>
CommitDate: Tue Apr 9 17:16:31 2024 +0100

x86/spec-ctrl: Expose BHI_CTRL to guests

The CPUID feature bit signals the presence of the BHI_DIS_S control in
SPEC_CTRL MSR, first available in Intel AlderLake and Sapphire Rapids CPUs

Xen already knows how to context switch MSR_SPEC_CTRL properly between guest
and hypervisor context.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
(cherry picked from commit 583f1d0950529f3517b1741c2b21a028a82ba831)
---
tools/misc/xen-cpuid.c | 1 +
xen/arch/x86/msr.c | 1 +
xen/include/asm-x86/msr-index.h | 1 +
xen/include/public/arch-x86/cpufeatureset.h | 1 +
xen/tools/gen-cpuid.py | 2 +-
5 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/misc/xen-cpuid.c b/tools/misc/xen-cpuid.c
index 350a7fdc45..6af86ba798 100644
--- a/tools/misc/xen-cpuid.c
+++ b/tools/misc/xen-cpuid.c
@@ -208,6 +208,7 @@ static const char *const str_7d2[32] =
{
[ 0] = "intel-psfd", [ 1] = "ipred-ctrl",
[ 2] = "rrsba-ctrl",
+ [ 4] = "bhi-ctrl",
};

static const char *const str_m10Al[32] =
diff --git a/xen/arch/x86/msr.c b/xen/arch/x86/msr.c
index 0000d4a4c2..4e67381d9a 100644
--- a/xen/arch/x86/msr.c
+++ b/xen/arch/x86/msr.c
@@ -325,6 +325,7 @@ uint64_t msr_spec_ctrl_valid_bits(const struct cpu_policy *cp)
? (SPEC_CTRL_IPRED_DIS_U | SPEC_CTRL_IPRED_DIS_S) : 0) |
(cp->feat.rrsba_ctrl
? (SPEC_CTRL_RRSBA_DIS_U | SPEC_CTRL_RRSBA_DIS_S) : 0) |
+ (cp->feat.bhi_ctrl ? SPEC_CTRL_BHI_DIS_S : 0) |
0);
}

diff --git a/xen/include/asm-x86/msr-index.h b/xen/include/asm-x86/msr-index.h
index b6c77049c4..5433ee199d 100644
--- a/xen/include/asm-x86/msr-index.h
+++ b/xen/include/asm-x86/msr-index.h
@@ -41,6 +41,7 @@
#define SPEC_CTRL_RRSBA_DIS_U (_AC(1, ULL) << 5)
#define SPEC_CTRL_RRSBA_DIS_S (_AC(1, ULL) << 6)
#define SPEC_CTRL_PSFD (_AC(1, ULL) << 7)
+#define SPEC_CTRL_BHI_DIS_S (_AC(1, ULL) << 10)

#define MSR_PRED_CMD 0x00000049
#define PRED_CMD_IBPB (_AC(1, ULL) << 0)
diff --git a/xen/include/public/arch-x86/cpufeatureset.h b/xen/include/public/arch-x86/cpufeatureset.h
index 0d333ae0b6..6e9fbcc38c 100644
--- a/xen/include/public/arch-x86/cpufeatureset.h
+++ b/xen/include/public/arch-x86/cpufeatureset.h
@@ -303,6 +303,7 @@ XEN_CPUFEATURE(SRSO_NO, 11*32+29) /*A Hardware not vulenrable to Spe
XEN_CPUFEATURE(INTEL_PSFD, 13*32+ 0) /*A MSR_SPEC_CTRL.PSFD */
XEN_CPUFEATURE(IPRED_CTRL, 13*32+ 1) /*A MSR_SPEC_CTRL.IPRED_DIS_* */
XEN_CPUFEATURE(RRSBA_CTRL, 13*32+ 2) /*A MSR_SPEC_CTRL.RRSBA_DIS_* */
+XEN_CPUFEATURE(BHI_CTRL, 13*32+ 4) /*A MSR_SPEC_CTRL.BHI_DIS_S */

/* Intel-defined CPU features, CPUID level 0x00000007:1.ecx, word 14 */

diff --git a/xen/tools/gen-cpuid.py b/xen/tools/gen-cpuid.py
index 6fc4392654..564477b392 100755
--- a/xen/tools/gen-cpuid.py
+++ b/xen/tools/gen-cpuid.py
@@ -316,7 +316,7 @@ def crunch_numbers(state):
# as dependent features simplifies Xen's logic, and prevents the guest
# from seeing implausible configurations.
IBRSB: [STIBP, SSBD, INTEL_PSFD, EIBRS,
- IPRED_CTRL, RRSBA_CTRL],
+ IPRED_CTRL, RRSBA_CTRL, BHI_CTRL],
IBRS: [AMD_STIBP, AMD_SSBD, PSFD,
IBRS_ALWAYS, IBRS_FAST, IBRS_SAME_MODE],
IBPB: [IBPB_RET, SBPB, IBPB_BRTYPE],
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.15