[xen staging] VT-d: Tylersburg isoch DMAR unit with no TLB space

[patchbot@xxxxxxx]

commit d3b05f9b16d6ba9c550c3a35ac11ed292bf87f68
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Oct 12 11:57:08 2021 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Oct 12 11:57:08 2021 +0200

    VT-d: Tylersburg isoch DMAR unit with no TLB space
    
    BIOSes, when enabling the dedicated DMAR unit for the sound device,
    need to also set a non-zero number of TLB entries in a respective
    system management register (VTISOCHCTRL). At least one BIOS is known
    to fail to do so, causing the VT-d engine to deadlock when used.
    
    Vaguely based on Linux'es e0fc7e0b4b5e ("intel-iommu: Yet another BIOS
    workaround: Isoch DMAR unit with no TLB space").
    
    To limit message string redundancy, fold parts with the IGD quirk logic.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
    Release-Acked-by: Ian Jackson <iwj@xxxxxxxxxxxxxx>
---
 xen/drivers/passthrough/vtd/extern.h |  1 +
 xen/drivers/passthrough/vtd/iommu.c  | 26 ++++++++++++---
 xen/drivers/passthrough/vtd/quirks.c | 63 ++++++++++++++++++++++++++++++++++++
 3 files changed, 85 insertions(+), 5 deletions(-)

diff --git a/xen/drivers/passthrough/vtd/extern.h 
b/xen/drivers/passthrough/vtd/extern.h
index 156177bb3f..6fb00a25c3 100644
--- a/xen/drivers/passthrough/vtd/extern.h
+++ b/xen/drivers/passthrough/vtd/extern.h
@@ -100,6 +100,7 @@ int msi_msg_write_remap_rte(struct msi_desc *, struct 
msi_msg *);
 int intel_setup_hpet_msi(struct msi_desc *);
 
 int is_igd_vt_enabled_quirk(void);
+bool is_azalia_tlb_enabled(const struct acpi_drhd_unit *);
 void platform_quirks_init(void);
 void vtd_ops_preamble_quirk(struct vtd_iommu *iommu);
 void vtd_ops_postamble_quirk(struct vtd_iommu *iommu);
diff --git a/xen/drivers/passthrough/vtd/iommu.c 
b/xen/drivers/passthrough/vtd/iommu.c
index 137aea2c92..0e7e111286 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -750,27 +750,43 @@ static void iommu_enable_translation(struct 
acpi_drhd_unit *drhd)
     u32 sts;
     unsigned long flags;
     struct vtd_iommu *iommu = drhd->iommu;
+    static const char crash_fmt[] = "%s; crash Xen for security purpose\n";
 
     if ( drhd->gfx_only )
     {
+        static const char disable_fmt[] = XENLOG_WARNING VTDPREFIX
+                                          " %s; disabling IGD VT-d engine\n";
+
         if ( !iommu_igfx )
         {
-            printk(XENLOG_INFO VTDPREFIX
-                   "Passed iommu=no-igfx option.  Disabling IGD VT-d 
engine.\n");
+            printk(disable_fmt, "passed iommu=no-igfx option");
             return;
         }
 
         if ( !is_igd_vt_enabled_quirk() )
         {
+            static const char msg[] = "firmware did not enable IGD for VT 
properly";
+
             if ( force_iommu )
-                panic("BIOS did not enable IGD for VT properly, crash Xen for 
security purpose\n");
+                panic(crash_fmt, msg);
 
-            printk(XENLOG_WARNING VTDPREFIX
-                   "BIOS did not enable IGD for VT properly.  Disabling IGD 
VT-d engine.\n");
+            printk(disable_fmt, msg);
             return;
         }
     }
 
+    if ( !is_azalia_tlb_enabled(drhd) )
+    {
+        static const char msg[] = "firmware did not enable TLB for sound 
device";
+
+        if ( force_iommu )
+            panic(crash_fmt, msg);
+
+        printk(XENLOG_WARNING VTDPREFIX " %s; disabling ISOCH VT-d engine\n",
+               msg);
+        return;
+    }
+
     /* apply platform specific errata workarounds */
     vtd_ops_preamble_quirk(iommu);
 
diff --git a/xen/drivers/passthrough/vtd/quirks.c 
b/xen/drivers/passthrough/vtd/quirks.c
index 2ad76a0ae7..52b47dd893 100644
--- a/xen/drivers/passthrough/vtd/quirks.c
+++ b/xen/drivers/passthrough/vtd/quirks.c
@@ -100,6 +100,69 @@ static void __init cantiga_b3_errata_init(void)
         is_cantiga_b3 = 1;
 }
 
+/*
+ * QUIRK to work around certain BIOSes enabling the ISOCH DMAR unit for the
+ * Azalia sound device, but not giving it any TLB entries, causing it to
+ * deadlock.
+ */
+bool is_azalia_tlb_enabled(const struct acpi_drhd_unit *drhd)
+{
+    pci_sbdf_t sbdf;
+    unsigned int vtisochctrl;
+
+    /* Only dedicated units are of interest. */
+    if ( drhd->include_all || drhd->scope.devices_cnt != 1 )
+        return true;
+
+    /* Check for the specific device. */
+    sbdf = PCI_SBDF2(drhd->segment, drhd->scope.devices[0]);
+    if ( pci_conf_read16(sbdf, PCI_VENDOR_ID) != PCI_VENDOR_ID_INTEL ||
+         pci_conf_read16(sbdf, PCI_DEVICE_ID) != 0x3a3e )
+        return true;
+
+    /* Check for the corresponding System Management Registers device. */
+    sbdf = PCI_SBDF(drhd->segment, 0, 0x14, 0);
+    if ( pci_conf_read16(sbdf, PCI_VENDOR_ID) != PCI_VENDOR_ID_INTEL ||
+         pci_conf_read16(sbdf, PCI_DEVICE_ID) != 0x342e )
+        return true;
+
+    vtisochctrl = pci_conf_read32(sbdf, 0x188);
+    if ( vtisochctrl == 0xffffffff )
+    {
+        printk(XENLOG_WARNING VTDPREFIX
+               " Cannot access VTISOCHCTRL at this time\n");
+        return true;
+    }
+
+    /*
+     * If Azalia DMA is routed to the non-isoch DMAR unit, that's fine in
+     * principle, but not consistent with the ACPI tables.
+     */
+    if ( vtisochctrl & 1 )
+    {
+        printk(XENLOG_WARNING VTDPREFIX
+               " Inconsistency between chipset registers and ACPI tables\n");
+        return true;
+    }
+
+    /* Drop all bits other than the number of TLB entries. */
+    vtisochctrl &= 0x1c;
+
+    /* If we have at least the recommended number of TLB entries, fine. */
+    if ( vtisochctrl >= 16 )
+        return true;
+
+    /* Zero TLB entries? */
+    if ( !vtisochctrl )
+        return false;
+
+    printk(XENLOG_WARNING VTDPREFIX
+           " Recommended TLB entries for ISOCH unit is 16; firmware set %u\n",
+           vtisochctrl);
+
+    return true;
+}
+
 /* check for Sandybridge IGD device ID's */
 static void __init snb_errata_init(void)
 {
--
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