Bug#971058: [PATCH] ACPI / extlog: Check for RDMSR failure

["Rafael J. Wysocki" <rafael@kernel.org>]

On Mon, Sep 28, 2020 at 12:27 AM Ben Hutchings <ben@decadent.org.uk> wrote:
>
> extlog_init() uses rdmsrl() to read an MSR, which on older CPUs
> provokes a error message at boot:
>
>     unchecked MSR access error: RDMSR from 0x179 at rIP: 0xcd047307 (native_read_msr+0x7/0x40)
>
> Use rdmsrl_safe() instead, and return -ENODEV if it fails.
>
> Reported-by: jim@photojim.ca
> References: https://bugs.debian.org/971058
> Cc: stable@vger.kernel.org
> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> ---
>  drivers/acpi/acpi_extlog.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/acpi/acpi_extlog.c b/drivers/acpi/acpi_extlog.c
> index f138e12b7b82..72f1fb77abcd 100644
> --- a/drivers/acpi/acpi_extlog.c
> +++ b/drivers/acpi/acpi_extlog.c
> @@ -222,9 +222,9 @@ static int __init extlog_init(void)
>         u64 cap;
>         int rc;
>
> -       rdmsrl(MSR_IA32_MCG_CAP, cap);
> -
> -       if (!(cap & MCG_ELOG_P) || !extlog_get_l1addr())
> +       if (rdmsrl_safe(MSR_IA32_MCG_CAP, &cap) ||
> +           !(cap & MCG_ELOG_P) ||
> +           !extlog_get_l1addr())
>                 return -ENODEV;
>
>         rc = -EINVAL;

Applied as 5.10 material, thanks!