lkml.org 
[lkml]   [2019]   [May]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
SubjectRe: [PATCH v2 6/7] iommu: Introduce IOMMU_RESV_DIRECT_RELAXABLE reserved memory regions
From
Date
Hi

On 5/16/19 10:47 AM, Eric Auger wrote:
> Introduce a new type for reserved region. This corresponds
> to directly mapped regions which are known to be relaxable
> in some specific conditions, such as device assignment use
> case. Well known examples are those used by USB controllers
> providing PS/2 keyboard emulation for pre-boot BIOS and
> early BOOT or RMRRs associated to IGD working in legacy mode.
>
> Since commit c875d2c1b808 ("iommu/vt-d: Exclude devices using RMRRs
> from IOMMU API domains") and commit 18436afdc11a ("iommu/vt-d: Allow
> RMRR on graphics devices too"), those regions are currently
> considered "safe" with respect to device assignment use case
> which requires a non direct mapping at IOMMU physical level
> (RAM GPA -> HPA mapping).
>
> Those RMRRs currently exist and sometimes the device is
> attempting to access it but this has not been considered
> an issue until now.
>
> However at the moment, iommu_get_group_resv_regions() is
> not able to make any difference between directly mapped
> regions: those which must be absolutely enforced and those
> like above ones which are known as relaxable.
>
> This is a blocker for reporting severe conflicts between
> non relaxable RMRRs (like MSI doorbells) and guest GPA space.
>
> With this new reserved region type we will be able to use
> iommu_get_group_resv_regions() to enumerate the IOVA space
> that is usable through the IOMMU API without introducing
> regressions with respect to existing device assignment
> use cases (USB and IGD).
>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>
> ---
>
> Note: At the moment the sysfs ABI is not changed. However I wonder
> whether it wouldn't be preferable to report the direct region as
> "direct_relaxed" there. At the moment, in case the same direct
> region is used by 2 devices, one USB/GFX and another not belonging
> to the previous categories, the direct region will be output twice
> with "direct" type.
>
> This would unblock Shameer's series:
> [PATCH v6 0/7] vfio/type1: Add support for valid iova list management
> https://patchwork.kernel.org/patch/10425309/
>
> which failed to get pulled for 4.18 merge window due to IGD
> device assignment regression.
> ---
> drivers/iommu/iommu.c | 12 +++++++-----
> include/linux/iommu.h | 6 ++++++
> 2 files changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index ae4ea5c0e6f9..84dcb6af6511 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -73,10 +73,11 @@ struct iommu_group_attribute {
> };
>
> static const char * const iommu_group_resv_type_string[] = {
> - [IOMMU_RESV_DIRECT] = "direct",
> - [IOMMU_RESV_RESERVED] = "reserved",
> - [IOMMU_RESV_MSI] = "msi",
> - [IOMMU_RESV_SW_MSI] = "msi",
> + [IOMMU_RESV_DIRECT] = "direct",
> + [IOMMU_RESV_DIRECT_RELAXABLE] = "direct",
> + [IOMMU_RESV_RESERVED] = "reserved",
> + [IOMMU_RESV_MSI] = "msi",
> + [IOMMU_RESV_SW_MSI] = "msi",
> };
>
> #define IOMMU_GROUP_ATTR(_name, _mode, _show, _store) \
> @@ -573,7 +574,8 @@ static int iommu_group_create_direct_mappings(struct iommu_group *group,
> start = ALIGN(entry->start, pg_size);
> end = ALIGN(entry->start + entry->length, pg_size);
>
> - if (entry->type != IOMMU_RESV_DIRECT)
> + if (entry->type != IOMMU_RESV_DIRECT ||
It must be a "&&" and not "||"

Respinning ...

Eric

> + entry->type != IOMMU_RESV_DIRECT_RELAXABLE)
> continue;
>
> for (addr = start; addr < end; addr += pg_size) {
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index ba91666998fb..14a521f85f14 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -135,6 +135,12 @@ enum iommu_attr {
> enum iommu_resv_type {
> /* Memory regions which must be mapped 1:1 at all times */
> IOMMU_RESV_DIRECT,
> + /*
> + * Memory regions which are advertised to be 1:1 but are
> + * commonly considered relaxable in some conditions,
> + * for instance in device assignment use case (USB, Graphics)
> + */
> + IOMMU_RESV_DIRECT_RELAXABLE,
> /* Arbitrary "never map this or give it to a device" address ranges */
> IOMMU_RESV_RESERVED,
> /* Hardware MSI region (untranslated) */
>

\
 
 \ /
  Last update: 2019-05-16 11:33    [W:0.043 / U:2.124 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site