[Xen-devel] [PATCH v2 5/6] libxc/pvh: set default MTRR type to write-back

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

And enable MTRR. This allows to provide a sane initial MTRR state for
PVH DomUs. This will have to be expanded when pci-passthrough support
is added to PVH guests, so that MMIO regions of devices are set as
UC.

Note that initial MTRR setup is done by hvmloader for HVM guests,
that's not used by PVH guests.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
----
Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 tools/libxc/xc_dom_x86.c | 44 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/tools/libxc/xc_dom_x86.c b/tools/libxc/xc_dom_x86.c
index e33a28847d..d28ff4d7e9 100644
--- a/tools/libxc/xc_dom_x86.c
+++ b/tools/libxc/xc_dom_x86.c
@@ -53,6 +53,9 @@
 #define X86_CR0_PE 0x01
 #define X86_CR0_ET 0x10
 
+#define MTRR_TYPE_WRBACK     6
+#define MTRR_DEF_TYPE_ENABLE (1u << 11)
+
 #define SPECIALPAGE_PAGING   0
 #define SPECIALPAGE_ACCESS   1
 #define SPECIALPAGE_SHARING  2
@@ -931,6 +934,20 @@ static int vcpu_x86_64(struct xc_dom_image *dom)
     return rc;
 }
 
+const static void *hvm_get_save_record(const void *ctx, unsigned int type,
+                                       unsigned int instance)
+{
+    const struct hvm_save_descriptor *header;
+
+    for ( header = ctx;
+          header->typecode != HVM_SAVE_CODE(END);
+          ctx += sizeof(*header) + header->length, header = ctx )
+        if ( header->typecode == type && header->instance == instance )
+            return ctx + sizeof(*header);
+
+    return NULL;
+}
+
 static int vcpu_hvm(struct xc_dom_image *dom)
 {
     struct {
@@ -938,9 +955,12 @@ static int vcpu_hvm(struct xc_dom_image *dom)
         HVM_SAVE_TYPE(HEADER) header;
         struct hvm_save_descriptor cpu_d;
         HVM_SAVE_TYPE(CPU) cpu;
+        struct hvm_save_descriptor mtrr_d;
+        HVM_SAVE_TYPE(MTRR) mtrr;
         struct hvm_save_descriptor end_d;
         HVM_SAVE_TYPE(END) end;
     } bsp_ctx;
+    const HVM_SAVE_TYPE(MTRR) *mtrr_record;
     uint8_t *full_ctx = NULL;
     int rc;
 
@@ -1014,6 +1034,30 @@ static int vcpu_hvm(struct xc_dom_image *dom)
     if ( dom->start_info_seg.pfn )
         bsp_ctx.cpu.rbx = dom->start_info_seg.pfn << PAGE_SHIFT;
 
+    /* Set the MTRR. */
+    bsp_ctx.mtrr_d.typecode = HVM_SAVE_CODE(MTRR);
+    bsp_ctx.mtrr_d.instance = 0;
+    bsp_ctx.mtrr_d.length = HVM_SAVE_LENGTH(MTRR);
+
+    mtrr_record = hvm_get_save_record(full_ctx, HVM_SAVE_CODE(MTRR), 0);
+    if ( !mtrr_record )
+    {
+        xc_dom_panic(dom->xch, XC_INTERNAL_ERROR,
+                     "%s: unable to get MTRR save record", __func__);
+        goto out;
+    }
+
+    memcpy(&bsp_ctx.mtrr, mtrr_record, sizeof(bsp_ctx.mtrr));
+
+    /* TODO: maybe this should be a firmware option instead? */
+    if ( !dom->device_model )
+        /*
+         * Enable MTRR, set default type to WB.
+         * TODO: add MMIO areas as UC when passthrough is supported.
+         */
+        bsp_ctx.mtrr.msr_mtrr_def_type = MTRR_TYPE_WRBACK |
+                                         MTRR_DEF_TYPE_ENABLE;
+
     /* Set the end descriptor. */
     bsp_ctx.end_d.typecode = HVM_SAVE_CODE(END);
     bsp_ctx.end_d.instance = 0;
-- 
2.17.0


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