Re: [PATCH v2 2/2] iommu/vt-d: skip invalid RMRR entries

Lu Baolu
2020-01-08T01:28:54Z

Hi,

On 1/8/20 3:16 AM, Barret Rhoden via iommu wrote:
> The VT-d docs specify requirements for the RMRR entries base and end
> (called 'Limit' in the docs) addresses.
>
> This commit will cause the DMAR processing to skip any RMRR entries that
> do not meet these requirements and mark the firmware as tainted, since
> the firmware is giving us junk.
>
> Signed-off-by: Barret Rhoden <brho@google.com>
> ---
> drivers/iommu/intel-iommu.c | 14 +++++++++++++-
> 1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index a8bb458845bc..32c3c6338a3d 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -4315,13 +4315,25 @@ static void __init init_iommu_pm_ops(void)
> static inline void init_iommu_pm_ops(void) {}
> #endif /* CONFIG_PM */
>
> +static int rmrr_validity_check(struct acpi_dmar_reserved_memory *rmrr)
> +{
> + if ((rmrr->base_address & PAGE_MASK) ||
> + (rmrr->end_address <= rmrr->base_address) ||
> + ((rmrr->end_address - rmrr->base_address + 1) & PAGE_MASK)) {
> + pr_err(FW_BUG "Broken RMRR base: %#018Lx end: %#018Lx\n",
> + rmrr->base_address, rmrr->end_address);

Since you will WARN_TAINT below, do you still want an error message
here?

> + return -EINVAL;
> + }
> + return 0;
> +}
> +
> int __init dmar_parse_one_rmrr(struct acpi_dmar_header *header, void *arg)
> {
> struct acpi_dmar_reserved_memory *rmrr;
> struct dmar_rmrr_unit *rmrru;
>
> rmrr = (struct acpi_dmar_reserved_memory *)header;
> - if (arch_rmrr_sanity_check(rmrr)) {
> + if (rmrr_validity_check(rmrr) || arch_rmrr_sanity_check(rmrr)) {
> WARN_TAINT(1, TAINT_FIRMWARE_WORKAROUND,
> "Your BIOS is broken; bad RMRR [%#018Lx-%#018Lx]\n"
> "BIOS vendor: %s; Ver: %s; Product Version: %s\n",
>

Best regards,
baolu