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Message-Id: <4-v1-ef02c60ddb76+12ca2-intel_no_snoop_jgg@nvidia.com>
Date: Tue, 5 Apr 2022 13:16:03 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Alex Williamson <alex.williamson@...hat.com>,
Lu Baolu <baolu.lu@...ux.intel.com>,
Christian Benvenuti <benve@...co.com>,
Cornelia Huck <cohuck@...hat.com>,
David Woodhouse <dwmw2@...radead.org>,
Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
iommu@...ts.linux-foundation.org, Jason Wang <jasowang@...hat.com>,
Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
linux-arm-msm@...r.kernel.org, linux-rdma@...r.kernel.org,
linux-s390@...r.kernel.org,
Matthew Rosato <mjrosato@...ux.ibm.com>,
"Michael S. Tsirkin" <mst@...hat.com>,
Nelson Escobar <neescoba@...co.com>, netdev@...r.kernel.org,
Rob Clark <robdclark@...il.com>,
Robin Murphy <robin.murphy@....com>,
Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
virtualization@...ts.linux-foundation.org,
Will Deacon <will@...nel.org>
Cc: Christoph Hellwig <hch@....de>,
"Tian, Kevin" <kevin.tian@...el.com>
Subject: [PATCH 4/5] vfio: Move the Intel no-snoop control off of IOMMU_CACHE
IOMMU_CACHE means "normal DMA to this iommu_domain's IOVA should be cache
coherent" and is used by the DMA API. The definition allows for special
non-coherent DMA to exist - ie processing of the no-snoop flag in PCIe
TLPs - so long as this behavior is opt-in by the device driver.
The flag is used by the DMA API and is always available if
dev_is_dma_coherent() is set.
For Intel IOMMU IOMMU_CACHE was redefined to mean 'force all DMA to be
cache coherent' which has the practical effect of causing the IOMMU to
ignore the no-snoop bit in a PCIe TLP.
x86 platforms are always IOMMU_CACHE, so Intel should ignore this flag.
Instead use the new domain op enforce_cache_coherency() which causes every
IOPTE created in the domain to have the no-snoop blocking behavior.
Reconfigure VFIO to always use IOMMU_CACHE and call
enforce_cache_coherency() to operate the special Intel behavior.
Remove the IOMMU_CACHE test from Intel IOMMU.
Ultimately VFIO plumbs the result of enforce_cache_coherency() back into
the x86 platform code through kvm_arch_register_noncoherent_dma() which
controls if the WBINVD instruction is available in the guest. No other
arch implements kvm_arch_register_noncoherent_dma().
Signed-off-by: Jason Gunthorpe <jgg@...dia.com>
---
drivers/iommu/intel/iommu.c | 3 +--
drivers/vfio/vfio_iommu_type1.c | 30 +++++++++++++++++++-----------
2 files changed, 20 insertions(+), 13 deletions(-)
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index f08611a6cc4799..0ca43671d934e9 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -4422,8 +4422,7 @@ static int intel_iommu_map(struct iommu_domain *domain,
prot |= DMA_PTE_READ;
if (iommu_prot & IOMMU_WRITE)
prot |= DMA_PTE_WRITE;
- if (((iommu_prot & IOMMU_CACHE) && dmar_domain->iommu_snooping) ||
- dmar_domain->enforce_no_snoop)
+ if (dmar_domain->enforce_no_snoop)
prot |= DMA_PTE_SNP;
max_addr = iova + size;
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 9394aa9444c10c..c13b9290e35759 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -84,8 +84,8 @@ struct vfio_domain {
struct iommu_domain *domain;
struct list_head next;
struct list_head group_list;
- int prot; /* IOMMU_CACHE */
- bool fgsp; /* Fine-grained super pages */
+ bool fgsp : 1; /* Fine-grained super pages */
+ bool enforce_cache_coherency : 1;
};
struct vfio_dma {
@@ -1461,7 +1461,7 @@ static int vfio_iommu_map(struct vfio_iommu *iommu, dma_addr_t iova,
list_for_each_entry(d, &iommu->domain_list, next) {
ret = iommu_map(d->domain, iova, (phys_addr_t)pfn << PAGE_SHIFT,
- npage << PAGE_SHIFT, prot | d->prot);
+ npage << PAGE_SHIFT, prot | IOMMU_CACHE);
if (ret)
goto unwind;
@@ -1771,7 +1771,7 @@ static int vfio_iommu_replay(struct vfio_iommu *iommu,
}
ret = iommu_map(domain->domain, iova, phys,
- size, dma->prot | domain->prot);
+ size, dma->prot | IOMMU_CACHE);
if (ret) {
if (!dma->iommu_mapped) {
vfio_unpin_pages_remote(dma, iova,
@@ -1859,7 +1859,7 @@ static void vfio_test_domain_fgsp(struct vfio_domain *domain)
return;
ret = iommu_map(domain->domain, 0, page_to_phys(pages), PAGE_SIZE * 2,
- IOMMU_READ | IOMMU_WRITE | domain->prot);
+ IOMMU_READ | IOMMU_WRITE | IOMMU_CACHE);
if (!ret) {
size_t unmapped = iommu_unmap(domain->domain, 0, PAGE_SIZE);
@@ -2267,8 +2267,15 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
goto out_detach;
}
- if (iommu_capable(bus, IOMMU_CAP_CACHE_COHERENCY))
- domain->prot |= IOMMU_CACHE;
+ /*
+ * If the IOMMU can block non-coherent operations (ie PCIe TLPs with
+ * no-snoop set) then VFIO always turns this feature on because on Intel
+ * platforms it optimizes KVM to disable wbinvd emulation.
+ */
+ if (domain->domain->ops->enforce_cache_coherency)
+ domain->enforce_cache_coherency =
+ domain->domain->ops->enforce_cache_coherency(
+ domain->domain);
/*
* Try to match an existing compatible domain. We don't want to
@@ -2279,7 +2286,8 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
*/
list_for_each_entry(d, &iommu->domain_list, next) {
if (d->domain->ops == domain->domain->ops &&
- d->prot == domain->prot) {
+ d->enforce_cache_coherency ==
+ domain->enforce_cache_coherency) {
iommu_detach_group(domain->domain, group->iommu_group);
if (!iommu_attach_group(d->domain,
group->iommu_group)) {
@@ -2611,14 +2619,14 @@ static void vfio_iommu_type1_release(void *iommu_data)
kfree(iommu);
}
-static int vfio_domains_have_iommu_cache(struct vfio_iommu *iommu)
+static int vfio_domains_have_enforce_cache_coherency(struct vfio_iommu *iommu)
{
struct vfio_domain *domain;
int ret = 1;
mutex_lock(&iommu->lock);
list_for_each_entry(domain, &iommu->domain_list, next) {
- if (!(domain->prot & IOMMU_CACHE)) {
+ if (!(domain->enforce_cache_coherency)) {
ret = 0;
break;
}
@@ -2641,7 +2649,7 @@ static int vfio_iommu_type1_check_extension(struct vfio_iommu *iommu,
case VFIO_DMA_CC_IOMMU:
if (!iommu)
return 0;
- return vfio_domains_have_iommu_cache(iommu);
+ return vfio_domains_have_enforce_cache_coherency(iommu);
default:
return 0;
}
--
2.35.1
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