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[PULL 2/3] target/arm: Set KVM_ARM_VCPU_SVE while probing the host
From: |
Peter Maydell |
Subject: |
[PULL 2/3] target/arm: Set KVM_ARM_VCPU_SVE while probing the host |
Date: |
Mon, 1 Aug 2022 16:36:04 +0100 |
From: Richard Henderson <richard.henderson@linaro.org>
Because we weren't setting this flag, our probe of ID_AA64ZFR0
was always returning zero. This also obviates the adjustment
of ID_AA64PFR0, which had sanitized the SVE field.
The effects of the bug are not visible, because the only thing that
ID_AA64ZFR0 is used for within qemu at present is tcg translation.
The other tests for SVE within KVM are via ID_AA64PFR0.SVE.
Reported-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220726045828.53697-3-richard.henderson@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
target/arm/kvm64.c | 27 +++++++++++++--------------
1 file changed, 13 insertions(+), 14 deletions(-)
diff --git a/target/arm/kvm64.c b/target/arm/kvm64.c
index bb1516b3d5a..43cd7eb8904 100644
--- a/target/arm/kvm64.c
+++ b/target/arm/kvm64.c
@@ -507,7 +507,6 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
bool sve_supported;
bool pmu_supported = false;
uint64_t features = 0;
- uint64_t t;
int err;
/* Old kernels may not know about the PREFERRED_TARGET ioctl: however
@@ -528,10 +527,17 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures
*ahcf)
struct kvm_vcpu_init init = { .target = -1, };
/*
- * Ask for Pointer Authentication if supported. We can't play the
- * SVE trick of synthesising the ID reg as KVM won't tell us
- * whether we have the architected or IMPDEF version of PAuth, so
- * we have to use the actual ID regs.
+ * Ask for SVE if supported, so that we can query ID_AA64ZFR0,
+ * which is otherwise RAZ.
+ */
+ sve_supported = kvm_arm_sve_supported();
+ if (sve_supported) {
+ init.features[0] |= 1 << KVM_ARM_VCPU_SVE;
+ }
+
+ /*
+ * Ask for Pointer Authentication if supported, so that we get
+ * the unsanitized field values for AA64ISAR1_EL1.
*/
if (kvm_arm_pauth_supported()) {
init.features[0] |= (1 << KVM_ARM_VCPU_PTRAUTH_ADDRESS |
@@ -675,20 +681,13 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures
*ahcf)
}
}
- sve_supported = kvm_arm_sve_supported();
-
- /* Add feature bits that can't appear until after VCPU init. */
if (sve_supported) {
- t = ahcf->isar.id_aa64pfr0;
- t = FIELD_DP64(t, ID_AA64PFR0, SVE, 1);
- ahcf->isar.id_aa64pfr0 = t;
-
/*
* There is a range of kernels between kernel commit 73433762fcae
* and f81cb2c3ad41 which have a bug where the kernel doesn't expose
* SYS_ID_AA64ZFR0_EL1 via the ONE_REG API unless the VM has enabled
- * SVE support, so we only read it here, rather than together with all
- * the other ID registers earlier.
+ * SVE support, which resulted in an error rather than RAZ.
+ * So only read the register if we set KVM_ARM_VCPU_SVE above.
*/
err |= read_sys_reg64(fdarray[2], &ahcf->isar.id_aa64zfr0,
ARM64_SYS_REG(3, 0, 0, 4, 4));
--
2.25.1