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iommu/amd: Use cmpxchg_double() when updating 128-bit IRTE

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When using 128-bit interrupt-remapping table entry (IRTE) (a.k.a GA mode),
current driver disables interrupt remapping when it updates the IRTE
so that the upper and lower 64-bit values can be updated safely.

However, this creates a small window, where the interrupt could
arrive and result in IO_PAGE_FAULT (for interrupt) as shown below.

  IOMMU Driver            Device IRQ
  ============            ===========
  irte.RemapEn=0
       ...
   change IRTE            IRQ from device ==> IO_PAGE_FAULT !!
       ...
  irte.RemapEn=1

This scenario has been observed when changing irq affinity on a system
running I/O-intensive workload, in which the destination APIC ID
in the IRTE is updated.

Instead, use cmpxchg_double() to update the 128-bit IRTE at once without
disabling the interrupt remapping. However, this means several features,
which require GA (128-bit IRTE) support will also be affected if cmpxchg16b
is not supported (which is unprecedented for AMD processors w/ IOMMU).

Fixes: 880ac60e25 ("iommu/amd: Introduce interrupt remapping ops structure")
Reported-by: Sean Osborne <sean.m.osborne@oracle.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Tested-by: Erik Rockstrom <erik.rockstrom@oracle.com>
Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
Link: https://lore.kernel.org/r/20200903093822.52012-3-suravee.suthikulpanit@amd.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Suravee Suthikulpanit 2020-09-03 09:38:22 +00:00 committed by Joerg Roedel
parent 26e495f341
commit e52d58d54a
3 changed files with 33 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/iommu/amd/Kconfig
View File

@ -10,7 +10,7 @@ config AMD_IOMMU
select IOMMU_API
select IOMMU_IOVA
select IOMMU_DMA
depends on X86_64 && PCI && ACPI
depends on X86_64 && PCI && ACPI && HAVE_CMPXCHG_DOUBLE
help
With this option you can enable support for AMD IOMMU hardware in
your system. An IOMMU is a hardware component which provides

21
drivers/iommu/amd/init.c
View File

@ -1511,7 +1511,14 @@ static int __init init_iommu_one(struct amd_iommu *iommu, struct ivhd_header *h)
iommu->mmio_phys_end = MMIO_REG_END_OFFSET;
else
iommu->mmio_phys_end = MMIO_CNTR_CONF_OFFSET;
if (((h->efr_attr & (0x1 << IOMMU_FEAT_GASUP_SHIFT)) == 0))
/*
* Note: GA (128-bit IRTE) mode requires cmpxchg16b supports.
* GAM also requires GA mode. Therefore, we need to
* check cmpxchg16b support before enabling it.
*/
if (!boot_cpu_has(X86_FEATURE_CX16) ||
((h->efr_attr & (0x1 << IOMMU_FEAT_GASUP_SHIFT)) == 0))
amd_iommu_guest_ir = AMD_IOMMU_GUEST_IR_LEGACY;
break;
case 0x11:
@ -1520,8 +1527,18 @@ static int __init init_iommu_one(struct amd_iommu *iommu, struct ivhd_header *h)
iommu->mmio_phys_end = MMIO_REG_END_OFFSET;
else
iommu->mmio_phys_end = MMIO_CNTR_CONF_OFFSET;
if (((h->efr_reg & (0x1 << IOMMU_EFR_GASUP_SHIFT)) == 0))
/*
* Note: GA (128-bit IRTE) mode requires cmpxchg16b supports.
* XT, GAM also requires GA mode. Therefore, we need to
* check cmpxchg16b support before enabling them.
*/
if (!boot_cpu_has(X86_FEATURE_CX16) ||
((h->efr_reg & (0x1 << IOMMU_EFR_GASUP_SHIFT)) == 0)) {
amd_iommu_guest_ir = AMD_IOMMU_GUEST_IR_LEGACY;
break;
}
/*
* Note: Since iommu_update_intcapxt() leverages
* the IOMMU MMIO access to MSI capability block registers

17
drivers/iommu/amd/iommu.c
View File

@ -3292,6 +3292,7 @@ static int alloc_irq_index(u16 devid, int count, bool align,
static int modify_irte_ga(u16 devid, int index, struct irte_ga *irte,
struct amd_ir_data *data)
{
bool ret;
struct irq_remap_table *table;
struct amd_iommu *iommu;
unsigned long flags;
@ -3309,10 +3310,18 @@ static int modify_irte_ga(u16 devid, int index, struct irte_ga *irte,
entry = (struct irte_ga *)table->table;
entry = &entry[index];
entry->lo.fields_remap.valid = 0;
entry->hi.val = irte->hi.val;
entry->lo.val = irte->lo.val;
entry->lo.fields_remap.valid = 1;
ret = cmpxchg_double(&entry->lo.val, &entry->hi.val,
entry->lo.val, entry->hi.val,
irte->lo.val, irte->hi.val);
/*
* We use cmpxchg16 to atomically update the 128-bit IRTE,
* and it cannot be updated by the hardware or other processors
* behind us, so the return value of cmpxchg16 should be the
* same as the old value.
*/
WARN_ON(!ret);
if (data)
data->ref = entry;