The branch main has been updated by kib: URL: https://cgit.FreeBSD.org/src/commit/?id=36ceb5509d01ff2e6482a78ca809c344574e9a25
commit 36ceb5509d01ff2e6482a78ca809c344574e9a25 Author: Konstantin Belousov <[email protected]> AuthorDate: 2026-02-04 00:24:58 +0000 Commit: Konstantin Belousov <[email protected]> CommitDate: 2026-02-13 07:55:04 +0000 x86_msr_op(9): consistently return the value read from MSR 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 --- sys/x86/x86/cpu_machdep.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) diff --git a/sys/x86/x86/cpu_machdep.c b/sys/x86/x86/cpu_machdep.c index 023b02ba7c76..6c3f4add6202 100644 --- a/sys/x86/x86/cpu_machdep.c +++ b/sys/x86/x86/cpu_machdep.c @@ -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();
