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Date: Fri, 9 Jul 2021 13:56:46 +0100
From: Robin Murphy <robin.murphy@....com>
To: Wei Liu <wei.liu@...nel.org>,
Linux on Hyper-V List <linux-hyperv@...r.kernel.org>
Cc: pasha.tatashin@...een.com, Will Deacon <will@...nel.org>,
kumarpraveen@...ux.microsoft.com,
David Woodhouse <dwmw2@...radead.org>,
Linux Kernel List <linux-kernel@...r.kernel.org>,
Michael Kelley <mikelley@...rosoft.com>,
"open list:INTEL IOMMU VT-d" <iommu@...ts.linux-foundation.org>,
Nuno Das Neves <nunodasneves@...ux.microsoft.com>,
Sunil Muthuswamy <sunilmut@...rosoft.com>,
virtualization@...ts.linux-foundation.org,
Vineeth Pillai <viremana@...ux.microsoft.com>,
Jean-Philippe Brucker <jean-philippe@...aro.org>
Subject: Re: [RFC v1 3/8] intel/vt-d: make DMAR table parsing code more
flexible
On 2021-07-09 12:43, Wei Liu wrote:
> Microsoft Hypervisor provides a set of hypercalls to manage device
> domains. The root kernel should parse the DMAR so that it can program
> the IOMMU (with hypercalls) correctly.
>
> The DMAR code was designed to work with Intel IOMMU only. Add two more
> parameters to make it useful to Microsoft Hypervisor. Microsoft
> Hypervisor does not need the DMAR parsing code to allocate an Intel
> IOMMU structure; it also wishes to always reparse the DMAR table even
> after it has been parsed before.
We've recently defined the VIOT table for describing paravirtualised
IOMMUs - would it make more sense to extend that to support the
Microsoft implementation than to abuse a hardware-specific table? Am I
right in assuming said hypervisor isn't intended to only ever run on
Intel hardware?
Robin.
> Adjust Intel IOMMU code to use the new dmar_table_init. There should be
> no functional change to Intel IOMMU code.
>
> Signed-off-by: Wei Liu <wei.liu@...nel.org>
> ---
> We may be able to combine alloc and force_parse?
> ---
> drivers/iommu/intel/dmar.c | 38 ++++++++++++++++++++---------
> drivers/iommu/intel/iommu.c | 2 +-
> drivers/iommu/intel/irq_remapping.c | 2 +-
> include/linux/dmar.h | 2 +-
> 4 files changed, 30 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
> index 84057cb9596c..bd72f47c728b 100644
> --- a/drivers/iommu/intel/dmar.c
> +++ b/drivers/iommu/intel/dmar.c
> @@ -408,7 +408,8 @@ dmar_find_dmaru(struct acpi_dmar_hardware_unit *drhd)
> * structure which uniquely represent one DMA remapping hardware unit
> * present in the platform
> */
> -static int dmar_parse_one_drhd(struct acpi_dmar_header *header, void *arg)
> +static int dmar_parse_one_drhd_internal(struct acpi_dmar_header *header,
> + void *arg, bool alloc)
> {
> struct acpi_dmar_hardware_unit *drhd;
> struct dmar_drhd_unit *dmaru;
> @@ -440,12 +441,14 @@ static int dmar_parse_one_drhd(struct acpi_dmar_header *header, void *arg)
> return -ENOMEM;
> }
>
> - ret = alloc_iommu(dmaru);
> - if (ret) {
> - dmar_free_dev_scope(&dmaru->devices,
> - &dmaru->devices_cnt);
> - kfree(dmaru);
> - return ret;
> + if (alloc) {
> + ret = alloc_iommu(dmaru);
> + if (ret) {
> + dmar_free_dev_scope(&dmaru->devices,
> + &dmaru->devices_cnt);
> + kfree(dmaru);
> + return ret;
> + }
> }
> dmar_register_drhd_unit(dmaru);
>
> @@ -456,6 +459,16 @@ static int dmar_parse_one_drhd(struct acpi_dmar_header *header, void *arg)
> return 0;
> }
>
> +static int dmar_parse_one_drhd(struct acpi_dmar_header *header, void *arg)
> +{
> + return dmar_parse_one_drhd_internal(header, arg, true);
> +}
> +
> +int dmar_parse_one_drhd_noalloc(struct acpi_dmar_header *header, void *arg)
> +{
> + return dmar_parse_one_drhd_internal(header, arg, false);
> +}
> +
> static void dmar_free_drhd(struct dmar_drhd_unit *dmaru)
> {
> if (dmaru->devices && dmaru->devices_cnt)
> @@ -633,7 +646,7 @@ static inline int dmar_walk_dmar_table(struct acpi_table_dmar *dmar,
> * parse_dmar_table - parses the DMA reporting table
> */
> static int __init
> -parse_dmar_table(void)
> +parse_dmar_table(bool alloc)
> {
> struct acpi_table_dmar *dmar;
> int drhd_count = 0;
> @@ -650,6 +663,9 @@ parse_dmar_table(void)
> .cb[ACPI_DMAR_TYPE_SATC] = &dmar_parse_one_satc,
> };
>
> + if (!alloc)
> + cb.cb[ACPI_DMAR_TYPE_HARDWARE_UNIT] = &dmar_parse_one_drhd_noalloc;
> +
> /*
> * Do it again, earlier dmar_tbl mapping could be mapped with
> * fixed map.
> @@ -840,13 +856,13 @@ void __init dmar_register_bus_notifier(void)
> }
>
>
> -int __init dmar_table_init(void)
> +int __init dmar_table_init(bool alloc, bool force_parse)
> {
> static int dmar_table_initialized;
> int ret;
>
> - if (dmar_table_initialized == 0) {
> - ret = parse_dmar_table();
> + if (dmar_table_initialized == 0 || force_parse) {
> + ret = parse_dmar_table(alloc);
> if (ret < 0) {
> if (ret != -ENODEV)
> pr_info("Parse DMAR table failure.\n");
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index be35284a2016..a4294d310b93 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -4310,7 +4310,7 @@ int __init intel_iommu_init(void)
> }
>
> down_write(&dmar_global_lock);
> - if (dmar_table_init()) {
> + if (dmar_table_init(true, false)) {
> if (force_on)
> panic("tboot: Failed to initialize DMAR table\n");
> goto out_free_dmar;
> diff --git a/drivers/iommu/intel/irq_remapping.c b/drivers/iommu/intel/irq_remapping.c
> index f912fe45bea2..0e8abef862e4 100644
> --- a/drivers/iommu/intel/irq_remapping.c
> +++ b/drivers/iommu/intel/irq_remapping.c
> @@ -732,7 +732,7 @@ static int __init intel_prepare_irq_remapping(void)
> return -ENODEV;
> }
>
> - if (dmar_table_init() < 0)
> + if (dmar_table_init(true, false) < 0)
> return -ENODEV;
>
> if (intel_cap_audit(CAP_AUDIT_STATIC_IRQR, NULL))
> diff --git a/include/linux/dmar.h b/include/linux/dmar.h
> index e04436a7ff27..f88535d41a6e 100644
> --- a/include/linux/dmar.h
> +++ b/include/linux/dmar.h
> @@ -106,7 +106,7 @@ static inline bool dmar_rcu_check(void)
> for_each_dev_scope((devs), (cnt), (i), (tmp)) \
> if (!(tmp)) { continue; } else
>
> -extern int dmar_table_init(void);
> +extern int dmar_table_init(bool alloc, bool force_parse);
> extern int dmar_dev_scope_init(void);
> extern void dmar_register_bus_notifier(void);
> extern int dmar_parse_dev_scope(void *start, void *end, int *cnt,
>
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