From b096d79bc1eed9eda57c12ccd76d6797cdba4cf2 Mon Sep 17 00:00:00 2001 From: Tim Wiederhake Date: Mon, 29 Jun 2026 19:37:59 +0200 Subject: [PATCH] x86/msr: Document the I/O-like write semantics in the msr driver Explain why msr_write() does not advance the index. [ bp: Massage commit message. ] Signed-off-by: Tim Wiederhake Signed-off-by: Borislav Petkov (AMD) Link: https://patch.msgid.link/20260629173759.1770596-1-twiederh@redhat.com --- arch/x86/kernel/msr.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c index 34bdb752f892..eb988df22521 100644 --- a/arch/x86/kernel/msr.c +++ b/arch/x86/kernel/msr.c @@ -13,6 +13,9 @@ * and then read/write in chunks of 8 bytes. A larger size means multiple * reads or writes of the same register. * + * Writing the same register multiple times can be useful for MSRs with + * I/O-like semantics, e.g. a virtual MSR that accepts logging information. + * * This driver uses /dev/cpu/%d/msr where %d is the minor number, and on * an SMP box will direct the access to CPU %d. */