From: Suravee Suthikulpanit suravee.suthikulpanit@amd.com
[ Upstream commit 66419036f68a838c00cbccacd6cb2e99da6e5710 ]
An Interrupt Remapping Table (IRT) stores interrupt remapping configuration for each device. In a normal operation, the AMD IOMMU caches the table to optimize subsequent data accesses. This requires the IOMMU driver to invalidate IRT whenever it updates the table. The invalidation process includes issuing an INVALIDATE_INTERRUPT_TABLE command following by a COMPLETION_WAIT command.
However, there are cases in which the IRT is updated at a high rate. For example, for IOMMU AVIC, the IRTE[IsRun] bit is updated on every vcpu scheduling (i.e. amd_iommu_update_ga()). On system with large amount of vcpus and VFIO PCI pass-through devices, the invalidation process could potentially become a performance bottleneck.
Introducing a new kernel boot option:
amd_iommu=irtcachedis
which disables IRTE caching by setting the IRTCachedis bit in each IOMMU Control register, and bypass the IRT invalidation process.
Reviewed-by: Jerry Snitselaar jsnitsel@redhat.com Co-developed-by: Alejandro Jimenez alejandro.j.jimenez@oracle.com Signed-off-by: Alejandro Jimenez alejandro.j.jimenez@oracle.com Signed-off-by: Suravee Suthikulpanit suravee.suthikulpanit@amd.com Link: https://lore.kernel.org/r/20230530141137.14376-4-suravee.suthikulpanit@amd.c... Signed-off-by: Joerg Roedel jroedel@suse.de Signed-off-by: Sasha Levin sashal@kernel.org --- .../admin-guide/kernel-parameters.txt | 1 + drivers/iommu/amd/amd_iommu_types.h | 4 +++ drivers/iommu/amd/init.c | 36 +++++++++++++++++++ 3 files changed, 41 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 286be425f3bfa..882b6198dd0d1 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -323,6 +323,7 @@ option with care. pgtbl_v1 - Use v1 page table for DMA-API (Default). pgtbl_v2 - Use v2 page table for DMA-API. + irtcachedis - Disable Interrupt Remapping Table (IRT) caching.
amd_iommu_dump= [HW,X86-64] Enable AMD IOMMU driver option to dump the ACPI table diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h index 5ecc17240eff5..f5e9377b55212 100644 --- a/drivers/iommu/amd/amd_iommu_types.h +++ b/drivers/iommu/amd/amd_iommu_types.h @@ -172,6 +172,7 @@ #define CONTROL_GAINT_EN 29 #define CONTROL_XT_EN 50 #define CONTROL_INTCAPXT_EN 51 +#define CONTROL_IRTCACHEDIS 59 #define CONTROL_SNPAVIC_EN 61
#define CTRL_INV_TO_MASK (7 << CONTROL_INV_TIMEOUT) @@ -708,6 +709,9 @@ struct amd_iommu { /* if one, we need to send a completion wait command */ bool need_sync;
+ /* true if disable irte caching */ + bool irtcachedis_enabled; + /* Handle for IOMMU core code */ struct iommu_device iommu;
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c index b0af8b5967e0d..f6e64c9858021 100644 --- a/drivers/iommu/amd/init.c +++ b/drivers/iommu/amd/init.c @@ -160,6 +160,7 @@ static int amd_iommu_xt_mode = IRQ_REMAP_XAPIC_MODE; static bool amd_iommu_detected; static bool amd_iommu_disabled __initdata; static bool amd_iommu_force_enable __initdata; +static bool amd_iommu_irtcachedis; static int amd_iommu_target_ivhd_type;
/* Global EFR and EFR2 registers */ @@ -477,6 +478,9 @@ static void iommu_disable(struct amd_iommu *iommu)
/* Disable IOMMU hardware itself */ iommu_feature_disable(iommu, CONTROL_IOMMU_EN); + + /* Clear IRTE cache disabling bit */ + iommu_feature_disable(iommu, CONTROL_IRTCACHEDIS); }
/* @@ -2700,6 +2704,33 @@ static void iommu_enable_ga(struct amd_iommu *iommu) #endif }
+static void iommu_disable_irtcachedis(struct amd_iommu *iommu) +{ + iommu_feature_disable(iommu, CONTROL_IRTCACHEDIS); +} + +static void iommu_enable_irtcachedis(struct amd_iommu *iommu) +{ + u64 ctrl; + + if (!amd_iommu_irtcachedis) + return; + + /* + * Note: + * The support for IRTCacheDis feature is dertermined by + * checking if the bit is writable. + */ + iommu_feature_enable(iommu, CONTROL_IRTCACHEDIS); + ctrl = readq(iommu->mmio_base + MMIO_CONTROL_OFFSET); + ctrl &= (1ULL << CONTROL_IRTCACHEDIS); + if (ctrl) + iommu->irtcachedis_enabled = true; + pr_info("iommu%d (%#06x) : IRT cache is %s\n", + iommu->index, iommu->devid, + iommu->irtcachedis_enabled ? "disabled" : "enabled"); +} + static void early_enable_iommu(struct amd_iommu *iommu) { iommu_disable(iommu); @@ -2710,6 +2741,7 @@ static void early_enable_iommu(struct amd_iommu *iommu) iommu_set_exclusion_range(iommu); iommu_enable_ga(iommu); iommu_enable_xt(iommu); + iommu_enable_irtcachedis(iommu); iommu_enable(iommu); iommu_flush_all_caches(iommu); } @@ -2760,10 +2792,12 @@ static void early_enable_iommus(void) for_each_iommu(iommu) { iommu_disable_command_buffer(iommu); iommu_disable_event_buffer(iommu); + iommu_disable_irtcachedis(iommu); iommu_enable_command_buffer(iommu); iommu_enable_event_buffer(iommu); iommu_enable_ga(iommu); iommu_enable_xt(iommu); + iommu_enable_irtcachedis(iommu); iommu_set_device_table(iommu); iommu_flush_all_caches(iommu); } @@ -3411,6 +3445,8 @@ static int __init parse_amd_iommu_options(char *str) amd_iommu_pgtable = AMD_IOMMU_V1; } else if (strncmp(str, "pgtbl_v2", 8) == 0) { amd_iommu_pgtable = AMD_IOMMU_V2; + } else if (strncmp(str, "irtcachedis", 11) == 0) { + amd_iommu_irtcachedis = true; } else { pr_notice("Unknown option - '%s'\n", str); }