[Xen-devel] [PATCH] [RFC] tools/hvmloader: Control ACPI debugging using a platform flag

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Since Qemu-trad
  c/s 147f83f9b7d87a698c200c4f3eb2d36a0e4fe54b
  "hw/piix4acpi: Make writes to ACPI_DBG_IO_ADDR actually work."

there has been quite a lot of extra logging appearing in the VM logs.

The hotplug debugging contributes 2 vmexits per slot per hotplug event, which
are simply a waste of time unless a developer is trying to debug VM
hotplugging problems.

Introduce a platform flag, "acpi-debug" to indicate in the AML whether
debugging writes are wanted or not.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Keir Fraser <keir@xxxxxxx>
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
CC: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
CC: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 docs/misc/xenstore-paths.markdown       |    1 +
 tools/firmware/hvmloader/acpi/build.c   |    5 +++++
 tools/firmware/hvmloader/acpi/dsdt.asl  |    1 +
 tools/firmware/hvmloader/acpi/mk_dsdt.c |    6 ++++++
 4 files changed, 13 insertions(+)

diff --git a/docs/misc/xenstore-paths.markdown 
b/docs/misc/xenstore-paths.markdown
index 70ab7f4..593a7b1 100644
--- a/docs/misc/xenstore-paths.markdown
+++ b/docs/misc/xenstore-paths.markdown
@@ -190,6 +190,7 @@ Various platform properties.
 * acpi -- is ACPI enabled for this domain
 * acpi_s3 -- is ACPI S3 support enabled for this domain
 * acpi_s4 -- is ACPI S4 support enabled for this domain
+* acpi-debug -- whether the AML code should write debugging messages to qemu
 
 #### ~/platform/generation-id = INTEGER ":" INTEGER [HVM,INTERNAL]
 
diff --git a/tools/firmware/hvmloader/acpi/build.c 
b/tools/firmware/hvmloader/acpi/build.c
index f1dd3f0..59716bb 100644
--- a/tools/firmware/hvmloader/acpi/build.c
+++ b/tools/firmware/hvmloader/acpi/build.c
@@ -47,6 +47,7 @@ struct acpi_info {
     uint8_t  com2_present:1;    /* 0[1] - System has COM2? */
     uint8_t  lpt1_present:1;    /* 0[2] - System has LPT1? */
     uint8_t  hpet_present:1;    /* 0[3] - System has HPET? */
+    uint8_t  acpi_debugging:1;  /* 0[4] - ACPI debugging enabled ? */
     uint32_t pci_min, pci_len;  /* 4, 8 - PCI I/O hole boundaries */
     uint32_t madt_csum_addr;    /* 12   - Address of MADT checksum */
     uint32_t madt_lapic0_addr;  /* 16   - Address of first MADT LAPIC struct */
@@ -404,6 +405,7 @@ void acpi_build_tables(struct acpi_config *config, unsigned 
int physical)
     unsigned char       *dsdt;
     unsigned long        secondary_tables[ACPI_MAX_SECONDARY_TABLES];
     int                  nr_secondaries, i;
+    const char          *xs_str;
 
     /* Allocate and initialise the acpi info area. */
     mem_hole_populate_ram(ACPI_INFO_PHYSICAL_ADDRESS >> PAGE_SHIFT, 1);
@@ -519,10 +521,13 @@ void acpi_build_tables(struct acpi_config *config, 
unsigned int physical)
     if ( !new_vm_gid(acpi_info) )
         goto oom;
 
+    xs_str = xenstore_read("platform/acpi-debug", "0");
+
     acpi_info->com1_present = uart_exists(0x3f8);
     acpi_info->com2_present = uart_exists(0x2f8);
     acpi_info->lpt1_present = lpt_exists(0x378);
     acpi_info->hpet_present = hpet_exists(ACPI_HPET_ADDRESS);
+    acpi_info->acpi_debugging = (xs_str[0] == '1');
     acpi_info->pci_min = pci_mem_start;
     acpi_info->pci_len = pci_mem_end - pci_mem_start;
 
diff --git a/tools/firmware/hvmloader/acpi/dsdt.asl 
b/tools/firmware/hvmloader/acpi/dsdt.asl
index 247a8ad..e753286 100644
--- a/tools/firmware/hvmloader/acpi/dsdt.asl
+++ b/tools/firmware/hvmloader/acpi/dsdt.asl
@@ -51,6 +51,7 @@ DefinitionBlock ("DSDT.aml", "DSDT", 2, "Xen", "HVM", 0)
            UAR2, 1,
            LTP1, 1,
            HPET, 1,
+           ADBG, 1,
            Offset(4),
            PMIN, 32,
            PLEN, 32,
diff --git a/tools/firmware/hvmloader/acpi/mk_dsdt.c 
b/tools/firmware/hvmloader/acpi/mk_dsdt.c
index a4b693b..3f0ca74 100644
--- a/tools/firmware/hvmloader/acpi/mk_dsdt.c
+++ b/tools/firmware/hvmloader/acpi/mk_dsdt.c
@@ -347,14 +347,18 @@ int main(int argc, char **argv)
             /* _SUN == dev */
             stmt("Name", "_SUN, 0x%08x", slot >> 3);
             push_block("Method", "_EJ0, 1");
+            push_block("If", "LEqual( \\_SB.ADBG, ONE )");
             stmt("Store", "0x%02x, \\_GPE.DPT1", slot);
             stmt("Store", "0x88, \\_GPE.DPT2");
+            pop_block();
             stmt("Store", "0x%02x, \\_GPE.PH%02X", /* eject */
                  (slot & 1) ? 0x10 : 0x01, slot & ~1);
             pop_block();
             push_block("Method", "_STA, 0");
+            push_block("If", "LEqual( \\_SB.ADBG, ONE )");
             stmt("Store", "0x%02x, \\_GPE.DPT1", slot);
             stmt("Store", "0x89, \\_GPE.DPT2");
+            pop_block();
             if ( slot & 1 )
                 stmt("ShiftRight", "0x4, \\_GPE.PH%02X, Local1", slot & ~1);
             else
@@ -426,8 +430,10 @@ int main(int argc, char **argv)
         stmt("Store", "PSTB, Local1"); /* XXX: Store (PSTB, SLT) ? */
         stmt("And", "Local1, 0xff, SLT");
         /* Debug */
+        push_block("If", "LEqual( \\_SB.ADBG, ONE )");
         stmt("Store", "SLT, DPT1");
         stmt("Store", "EVT, DPT2");
+        pop_block();
         /* Decision tree */
         decision_tree(0x00, 0x100, "SLT", pci_hotplug_notify);
         pop_block();
-- 
1.7.10.4


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