[xen staging] xen/arm: introduce direct-map for domUs

[patchbot@xxxxxxx]

commit 75591dcfe0341def8dfc79fb7ef19f89fb3de327
Author:     Penny Zheng <penny.zheng@xxxxxxx>
AuthorDate: Mon Feb 14 03:19:50 2022 +0000
Commit:     Julien Grall <jgrall@xxxxxxxxxx>
CommitDate: Thu Feb 17 19:43:02 2022 +0000

    xen/arm: introduce direct-map for domUs
    
    Cases where domU needs direct-map memory map:
      * IOMMU not present in the system.
      * IOMMU disabled if it doesn't cover a specific device and all the guests
    are trusted. Thinking a mixed scenario, where a few devices with IOMMU and
    a few without, then guest DMA security still could not be totally 
guaranteed.
    So users may want to disable the IOMMU, to at least gain some performance
    improvement from IOMMU disabled.
      * IOMMU disabled as a workaround when it doesn't have enough bandwidth.
    To be specific, in a few extreme situation, when multiple devices do DMA
    concurrently, these requests may exceed IOMMU's transmission capacity.
      * IOMMU disabled when it adds too much latency on DMA. For example,
    TLB may be missing in some IOMMU hardware, which may bring latency in DMA
    progress, so users may want to disable it in some realtime scenario.
      * Guest OS relies on the host memory layout
    
    This commit introduces a new helper assign_static_memory_11 to allocate
    static memory as guest RAM for direct-map domain.
    
    Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
    Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
    Tested-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
 xen/arch/arm/domain_build.c | 97 +++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 94 insertions(+), 3 deletions(-)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index e61d2d53ba..ec29bd302c 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -494,8 +494,17 @@ static bool __init append_static_memory_to_bank(struct 
domain *d,
 {
     int res;
     unsigned int nr_pages = PFN_DOWN(size);
-    /* Infer next GFN. */
-    gfn_t sgfn = gaddr_to_gfn(bank->start + bank->size);
+    gfn_t sgfn;
+
+    /*
+     * For direct-mapped domain, the GFN match the MFN.
+     * Otherwise, this is inferred on what has already been allocated
+     * in the bank.
+     */
+    if ( !is_domain_direct_mapped(d) )
+        sgfn = gaddr_to_gfn(bank->start + bank->size);
+    else
+        sgfn = gaddr_to_gfn(mfn_to_maddr(smfn));
 
     res = guest_physmap_add_pages(d, sgfn, smfn, nr_pages);
     if ( res )
@@ -668,12 +677,92 @@ static void __init allocate_static_memory(struct domain 
*d,
  fail:
     panic("Failed to allocate requested static memory for domain %pd.", d);
 }
+
+/*
+ * Allocate static memory as RAM for one specific domain d.
+ * The static memory will be directly mapped in the guest(Guest Physical
+ * Address == Physical Address).
+ */
+static void __init assign_static_memory_11(struct domain *d,
+                                           struct kernel_info *kinfo,
+                                           const struct dt_device_node *node)
+{
+    u32 addr_cells, size_cells, reg_cells;
+    unsigned int nr_banks, bank = 0;
+    const __be32 *cell;
+    paddr_t pbase, psize;
+    mfn_t smfn;
+    int length;
+
+    if ( parse_static_mem_prop(node, &addr_cells, &size_cells, &length, &cell) 
)
+    {
+        printk(XENLOG_ERR
+               "%pd: failed to parse \"xen,static-mem\" property.\n", d);
+        goto fail;
+    }
+    reg_cells = addr_cells + size_cells;
+    nr_banks = length / (reg_cells * sizeof(u32));
+
+    if ( nr_banks > NR_MEM_BANKS )
+    {
+        printk(XENLOG_ERR
+               "%pd: exceed max number of supported guest memory banks.\n", d);
+        goto fail;
+    }
+
+    for ( ; bank < nr_banks; bank++ )
+    {
+        smfn = acquire_static_memory_bank(d, &cell, addr_cells, size_cells,
+                                          &pbase, &psize);
+        if ( mfn_eq(smfn, INVALID_MFN) )
+            goto fail;
+
+        printk(XENLOG_INFO "%pd: STATIC BANK[%u] %#"PRIpaddr"-%#"PRIpaddr"\n",
+               d, bank, pbase, pbase + psize);
+
+        /* One guest memory bank is matched with one physical memory bank. */
+        kinfo->mem.bank[bank].start = pbase;
+        if ( !append_static_memory_to_bank(d, &kinfo->mem.bank[bank],
+                                           smfn, psize) )
+            goto fail;
+
+        kinfo->unassigned_mem -= psize;
+    }
+
+    kinfo->mem.nr_banks = nr_banks;
+
+    /*
+     * The property 'memory' should match the amount of memory given to
+     * the guest.
+     * Currently, it is only possible to either acquire static memory or
+     * let Xen allocate. *Mixing* is not supported.
+     */
+    if ( kinfo->unassigned_mem != 0 )
+    {
+        printk(XENLOG_ERR
+               "Size of \"memory\" property doesn't match up with the sum-up 
of \"xen,static-mem\".\n");
+        goto fail;
+    }
+
+    return;
+
+ fail:
+    panic("Failed to assign requested static memory for direct-map domain 
%pd.",
+          d);
+}
 #else
 static void __init allocate_static_memory(struct domain *d,
                                           struct kernel_info *kinfo,
                                           const struct dt_device_node *node)
 {
 }
+
+static void __init assign_static_memory_11(struct domain *d,
+                                           struct kernel_info *kinfo,
+                                           const struct dt_device_node *node)
+{
+    ASSERT_UNREACHABLE();
+}
 #endif
 
 /*
@@ -3023,8 +3112,10 @@ static int __init construct_domU(struct domain *d,
 #endif
     if ( !dt_find_property(node, "xen,static-mem", NULL) )
         allocate_memory(d, &kinfo);
-    else
+    else if ( !is_domain_direct_mapped(d) )
         allocate_static_memory(d, &kinfo, node);
+    else
+        assign_static_memory_11(d, &kinfo, node);
 
     rc = prepare_dtb_domU(d, &kinfo);
     if ( rc < 0 )
--
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