[Xen-devel] [PATCH] [RFC] xen/arm: Restrict "pa_range" according to the IOMMU requirements

[Oleksandr Tyshchenko <olekstysh@gmail.com>]

From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>

There is a strict requirement for the IOMMU which wants to share
the P2M table with the CPU. The maximum supported by the IOMMU
Stage-2 input size must be greater or equal to the P2M IPA size.

So, first initialize the IOMMU and gather the requirements and
then initialize the P2M. In the P2M code, take into the account
the IOMMU requirements and restrict "pa_range" if necessary.

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
---

CC: Julien Grall <julien.grall@arm.com>

Why RFC?

1. Patch assumes that IPMMU support is already in.
2. Not sure for the SMMU.

If there are no objections I will craft a proper patch.
---
 xen/arch/arm/p2m.c                       | 19 +++++++++++++++++--
 xen/arch/arm/setup.c                     |  4 ++--
 xen/drivers/passthrough/arm/ipmmu-vmsa.c | 20 +++++---------------
 xen/drivers/passthrough/arm/smmu.c       | 14 +++++++-------
 4 files changed, 31 insertions(+), 26 deletions(-)

diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index c171568..1262ae9 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -34,7 +34,7 @@ static unsigned int __read_mostly max_vmid = MAX_VMID_8_BIT;
 
 #define P2M_ROOT_PAGES    (1<<P2M_ROOT_ORDER)
 
-unsigned int __read_mostly p2m_ipa_bits;
+unsigned int __read_mostly p2m_ipa_bits = 0;
 
 /* Helpers to lookup the properties of each level */
 static const paddr_t level_masks[] =
@@ -1981,10 +1981,25 @@ void __init setup_virt_paging(void)
         [7] = { 0 }  /* Invalid */
     };
 
-    unsigned int cpu;
+    unsigned int i, cpu;
     unsigned int pa_range = 0x10; /* Larger than any possible value */
     bool vmid_8_bit = false;
 
+    if ( iommu_enabled )
+    {
+        /* We expect "p2m_ipa_bits" to be updated by the IOMMU driver */
+        ASSERT(p2m_ipa_bits);
+
+        /* We need to restrict "pa_range" according to the IOMMU requirements */
+        for ( i = 0; i < ARRAY_SIZE(pa_range_info); i++ )
+        {
+            if ( p2m_ipa_bits >= 64 - pa_range_info[i].t0sz )
+                pa_range = i;
+            else
+                break;
+        }
+    }
+
     for_each_online_cpu ( cpu )
     {
         const struct cpuinfo_arm *info = &cpu_data[cpu];
diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index 51a6677..01cd83d 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -936,12 +936,12 @@ void __init start_xen(unsigned long boot_phys_offset,
     printk("Brought up %ld CPUs\n", (long)num_online_cpus());
     /* TODO: smp_cpus_done(); */
 
-    setup_virt_paging();
-
     rc = iommu_setup();
     if ( !iommu_enabled && rc != -ENODEV )
         panic("Couldn't configure correctly all the IOMMUs.");
 
+    setup_virt_paging();
+
     do_initcalls();
 
     /*
diff --git a/xen/drivers/passthrough/arm/ipmmu-vmsa.c b/xen/drivers/passthrough/arm/ipmmu-vmsa.c
index ec543c3..0dc6351 100644
--- a/xen/drivers/passthrough/arm/ipmmu-vmsa.c
+++ b/xen/drivers/passthrough/arm/ipmmu-vmsa.c
@@ -526,6 +526,7 @@ static int ipmmu_domain_init_context(struct ipmmu_vmsa_domain *domain)
      * to TTBR0. Use 4KB page granule. Start page table walks at first level.
      * Always bypass stage 1 translation.
      */
+    ASSERT(p2m_ipa_bits <= IPMMU_MAX_P2M_IPA_BITS);
     tsz0 = (64 - p2m_ipa_bits) << IMTTBCR_TSZ0_SHIFT;
     ipmmu_ctx_write_root(domain, IMTTBCR, IMTTBCR_EAE | IMTTBCR_PMB |
                          IMTTBCR_SL0_LVL_1 | tsz0);
@@ -1314,23 +1315,12 @@ static __init int ipmmu_init(struct dt_device_node *node, const void *data)
         return -ENODEV;
     }
     else
-    {
         /*
-         * As 4-level translation table is not supported in IPMMU, we need
-         * to check IPA size used for P2M table beforehand to be sure it is
-         * 3-level and the IPMMU will be able to use it.
-         *
-         * TODO: First initialize the IOMMU and gather the requirements and
-         * then initialize the P2M. In the P2M code, take into the account
-         * the IOMMU requirements and restrict "pa_range" if necessary.
+         * Set max Stage-2 input size supported by the IPMMU. We expect
+         * the P2M code will take into the account the IOMMU requirements and
+         * restrict "pa_range" if necessary.
          */
-        if ( IPMMU_MAX_P2M_IPA_BITS < p2m_ipa_bits )
-        {
-            printk_once(XENLOG_ERR "ipmmu: P2M IPA size is not supported (P2M=%u IPMMU=%u)!\n",
-                        p2m_ipa_bits, IPMMU_MAX_P2M_IPA_BITS);
-            return -ENODEV;
-        }
-    }
+        p2m_ipa_bits = IPMMU_MAX_P2M_IPA_BITS;
 
     ret = ipmmu_probe(node);
     if ( ret )
diff --git a/xen/drivers/passthrough/arm/smmu.c b/xen/drivers/passthrough/arm/smmu.c
index 8ae986a..9b3867d 100644
--- a/xen/drivers/passthrough/arm/smmu.c
+++ b/xen/drivers/passthrough/arm/smmu.c
@@ -1110,6 +1110,7 @@ static void arm_smmu_init_context_bank(struct arm_smmu_domain *smmu_domain)
 			reg = TTBCR_TG0_64K;
 
 		if (!stage1) {
+			ASSERT(p2m_ipa_bits <= smmu->s2_input_size);
 			reg |= (64 - smmu->s2_input_size) << TTBCR_T0SZ_SHIFT;
 
 			switch (smmu->s2_output_size) {
@@ -2198,13 +2199,12 @@ static int arm_smmu_device_cfg_probe(struct arm_smmu_device *smmu)
 	size = arm_smmu_id_size_to_bits((id >> ID2_IAS_SHIFT) & ID2_IAS_MASK);
 	smmu->s1_output_size = min_t(unsigned long, PHYS_MASK_SHIFT, size);
 
-	/* Xen: Stage-2 input size has to match p2m_ipa_bits.  */
-	if (size < p2m_ipa_bits) {
-		dev_err(smmu->dev,
-			"P2M IPA size not supported (P2M=%u SMMU=%lu)!\n",
-			p2m_ipa_bits, size);
-		return -ENODEV;
-	}
+	/*
+	 * Xen: Set max Stage-2 input size supported by the SMMU. We expect
+	 * the P2M code will take into the account the IOMMU requirements and
+	 * restrict "pa_range" if necessary.
+	 */
+	p2m_ipa_bits = size;
 	smmu->s2_input_size = p2m_ipa_bits;
 #if 0
 	/* Stage-2 input size limited due to pgd allocation (PTRS_PER_PGD) */
-- 
2.7.4


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