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x86_msr_op(9): consistently return the value read from MSR

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If the operation is executed on more than one CPU, a random instance of
the read value is returned.

Reviewed by:	markj, olce
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D55045
This commit is contained in:
Konstantin Belousov
2026-02-04 02:24:58 +02:00
parent af99e40af1
commit 36ceb5509d
1 changed files with 15 additions and 4 deletions
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sys/x86/x86/cpu_machdep.c
+15 -4
View File
@@ -136,6 +136,8 @@ x86_msr_op_one_safe(struct msr_op_arg *a)
atomic_cmpset_int(&a->error, 0, error);
break;
}
if (a->res != NULL)
atomic_store_64(a->res, v);
v &= ~a->arg1;
error = wrmsr_safe(a->msr, v);
if (error != 0)
@@ -147,6 +149,8 @@ x86_msr_op_one_safe(struct msr_op_arg *a)
atomic_cmpset_int(&a->error, 0, error);
break;
}
if (a->res != NULL)
atomic_store_64(a->res, v);
v |= a->arg1;
error = wrmsr_safe(a->msr, v);
if (error != 0)
@@ -159,10 +163,12 @@ x86_msr_op_one_safe(struct msr_op_arg *a)
break;
case MSR_OP_READ:
error = rdmsr_safe(a->msr, &v);
if (error == 0)
*a->res = v;
else
if (error == 0) {
if (a->res != NULL)
atomic_store_64(a->res, v);
} else {
atomic_cmpset_int(&a->error, 0, error);
}
break;
}
}
@@ -175,11 +181,15 @@ x86_msr_op_one_unsafe(struct msr_op_arg *a)
switch (a->op) {
case MSR_OP_ANDNOT:
v = rdmsr(a->msr);
if (a->res != NULL)
atomic_store_64(a->res, v);
v &= ~a->arg1;
wrmsr(a->msr, v);
break;
case MSR_OP_OR:
v = rdmsr(a->msr);
if (a->res != NULL)
atomic_store_64(a->res, v);
v |= a->arg1;
wrmsr(a->msr, v);
break;
@@ -188,7 +198,8 @@ x86_msr_op_one_unsafe(struct msr_op_arg *a)
break;
case MSR_OP_READ:
v = rdmsr(a->msr);
*a->res = v;
if (a->res != NULL)
atomic_store_64(a->res, v);
break;
default:
__assert_unreachable();