Re: [Qemu-devel] Commit 77af8a2b95b79699de650965d5228772743efe84 breaks Windows 2000 support

[Paolo Bonzini <pbonzini@redhat.com>]

On 25/07/2017 18:23, Paolo Bonzini wrote:
> On 25/07/2017 18:14, Laszlo Ersek wrote:
>>   "No regressions became apparent in tests with a range of Windows
>>    (XP-10)"
>>
>> In theory, w2k falls within that range.
> 
> Nope, Windows 2000 is like NT 5.0, XP is like NT 5.1. :(
> 
> One possibility is to fix it in SeaBIOS instead: if you get a 2.0 FADT
> and an XSDT and no RSDT, it can build an RSDT and a 1.0 FADT itself,
> patching the RSDT to point to it.
> 
> It's a hack, but it's the only place I see to make it "just work".  And
> it could be extended nicely in the future.
> 
> All QEMU would have to do is to provide an XSDT _instead_ of an RSDT.

Completely untested code follows.  Machine type compatibility code 
should not be necessary because new QEMU always starts with a new BIOS.

Not sure I'll have much time for this in the next few days, so help
is appreciated.

Paolo

QEMU:

diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
index 36a6cc450e..ea750d54d9 100644
--- a/hw/acpi/aml-build.c
+++ b/hw/acpi/aml-build.c
@@ -1573,33 +1573,6 @@ void acpi_build_tables_cleanup(AcpiBuildTables *tables, bool mfre)
     g_array_free(tables->vmgenid, mfre);
 }
 
-/* Build rsdt table */
-void
-build_rsdt(GArray *table_data, BIOSLinker *linker, GArray *table_offsets,
-           const char *oem_id, const char *oem_table_id)
-{
-    int i;
-    unsigned rsdt_entries_offset;
-    AcpiRsdtDescriptorRev1 *rsdt;
-    const unsigned table_data_len = (sizeof(uint32_t) * table_offsets->len);
-    const unsigned rsdt_entry_size = sizeof(rsdt->table_offset_entry[0]);
-    const size_t rsdt_len = sizeof(*rsdt) + table_data_len;
-
-    rsdt = acpi_data_push(table_data, rsdt_len);
-    rsdt_entries_offset = (char *)rsdt->table_offset_entry - table_data->data;
-    for (i = 0; i < table_offsets->len; ++i) {
-        uint32_t ref_tbl_offset = g_array_index(table_offsets, uint32_t, i);
-        uint32_t rsdt_entry_offset = rsdt_entries_offset + rsdt_entry_size * i;
-
-        /* rsdt->table_offset_entry to be filled by Guest linker */
-        bios_linker_loader_add_pointer(linker,
-            ACPI_BUILD_TABLE_FILE, rsdt_entry_offset, rsdt_entry_size,
-            ACPI_BUILD_TABLE_FILE, ref_tbl_offset);
-    }
-    build_header(linker, table_data,
-                 (void *)rsdt, "RSDT", rsdt_len, 1, oem_id, oem_table_id);
-}
-
 /* Build xsdt table */
 void
 build_xsdt(GArray *table_data, BIOSLinker *linker, GArray *table_offsets,
diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 6b7bade183..ad00f6affd 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -2557,12 +2557,12 @@ build_amd_iommu(GArray *table_data, BIOSLinker *linker)
 }
 
 static GArray *
-build_rsdp(GArray *rsdp_table, BIOSLinker *linker, unsigned rsdt_tbl_offset)
+build_rsdp(GArray *rsdp_table, BIOSLinker *linker, unsigned xsdt_tbl_offset)
 {
     AcpiRsdpDescriptor *rsdp = acpi_data_push(rsdp_table, sizeof *rsdp);
-    unsigned rsdt_pa_size = sizeof(rsdp->rsdt_physical_address);
-    unsigned rsdt_pa_offset =
-        (char *)&rsdp->rsdt_physical_address - rsdp_table->data;
+    unsigned xsdt_pa_size = sizeof(rsdp->xsdt_physical_address);
+    unsigned xsdt_pa_offset =
+        (char *)&rsdp->xsdt_physical_address - rsdp_table->data;
 
     bios_linker_loader_alloc(linker, ACPI_BUILD_RSDP_FILE, rsdp_table, 16,
                              true /* fseg memory */);
@@ -2571,8 +2571,8 @@ build_rsdp(GArray *rsdp_table, BIOSLinker *linker, unsigned rsdt_tbl_offset)
     memcpy(rsdp->oem_id, ACPI_BUILD_APPNAME6, 6);
     /* Address to be filled by Guest linker */
     bios_linker_loader_add_pointer(linker,
-        ACPI_BUILD_RSDP_FILE, rsdt_pa_offset, rsdt_pa_size,
-        ACPI_BUILD_TABLE_FILE, rsdt_tbl_offset);
+        ACPI_BUILD_RSDP_FILE, xsdt_pa_offset, xsdt_pa_size,
+        ACPI_BUILD_TABLE_FILE, xsdt_tbl_offset);
 
     /* Checksum to be filled by Guest linker */
     bios_linker_loader_add_checksum(linker, ACPI_BUILD_RSDP_FILE,
@@ -2621,7 +2621,7 @@ void acpi_build(AcpiBuildTables *tables, MachineState *machine)
     PCMachineState *pcms = PC_MACHINE(machine);
     PCMachineClass *pcmc = PC_MACHINE_GET_CLASS(pcms);
     GArray *table_offsets;
-    unsigned facs, dsdt, rsdt, fadt;
+    unsigned facs, dsdt, xsdt, fadt;
     AcpiPmInfo pm;
     AcpiMiscInfo misc;
     AcpiMcfgInfo mcfg;
@@ -2730,12 +2730,12 @@ void acpi_build(AcpiBuildTables *tables, MachineState *machine)
     }
 
     /* RSDT is pointed to by RSDP */
-    rsdt = tables_blob->len;
-    build_rsdt(tables_blob, tables->linker, table_offsets,
+    xsdt = tables_blob->len;
+    build_xsdt(tables_blob, tables->linker, table_offsets,
                slic_oem.id, slic_oem.table_id);
 
     /* RSDP is in FSEG memory, so allocate it separately */
-    build_rsdp(tables->rsdp, tables->linker, rsdt);
+    build_rsdp(tables->rsdp, tables->linker, xsdt);
 
     /* We'll expose it all to Guest so we want to reduce
      * chance of size changes.


SeaBIOS:

>From 73b0facdb7349f5dbf24dc675647b68eeeec0ff4 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Tue, 25 Jul 2017 18:50:19 +0200
Subject: [PATCH 1/2] seabios: build RSDT from XSDT

Old operating systems would like to have a v1 FADT, but new
operating systems would like to have v3.

Since old operating systems do not know about XSDTs, the
solution is to point the RSDT to a v1 FADT and the XSDT to a
v3 FADT.

But, OVMF is not able to do that and barfs when it sees the
second FADT---plus really it's only BIOS operating systems
such as win2k that complain.  So instead: 1) make QEMU provide
an XSDT only; 2) build the RSDT and v1 FADT in SeaBIOS.

This patch makes SeaBIOS build an RSDT out of an existing XSDT.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 src/fw/paravirt.c | 45 ++++++++++++++++++++++++++++++++++++++++++++-
 src/std/acpi.h    | 11 +++++++++++
 2 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/src/fw/paravirt.c b/src/fw/paravirt.c
index 5b23d78..19a4abe 100644
--- a/src/fw/paravirt.c
+++ b/src/fw/paravirt.c
@@ -25,6 +25,7 @@
 #include "x86.h" // cpuid
 #include "xen.h" // xen_biostable_setup
 #include "stacks.h" // yield
+#include "std/acpi.h"
 
 // Amount of continuous ram under 4Gig
 u32 RamSize;
@@ -147,6 +148,46 @@ static void msr_feature_control_setup(void)
         wrmsr_smp(MSR_IA32_FEATURE_CONTROL, feature_control_bits);
 }
 
+static void
+build_compatibility_rsdt(void)
+{
+    if (RsdpAddr->rsdt_physical_address)
+        return;
+
+    u64 xsdt_addr = RsdpAddr->xsdt_physical_address;
+    if (xsdt_addr & ~0xffffffffULL)
+        return;
+
+    struct xsdt_descriptor_rev1 *xsdt = (void*)(u32)xsdt_addr;
+    void *end = (void*)xsdt + xsdt->length;
+    struct rsdt_descriptor_rev1 *rsdt;
+    int rsdt_size = offsetof(struct rsdt_descriptor_rev1, table_offset_entry[0]);
+    int i;
+    for (i=0; (void*)&xsdt->table_offset_entry[i] < end; i++) {
+        u64 tbl_addr = xsdt->table_offset_entry[i];
+        if (!tbl_addr || (tbl_addr & ~0xffffffffULL))
+            continue;
+        rsdt_size += 4;
+    }
+
+    rsdt = malloc_high(rsdt_size);
+    RsdpAddr->rsdt_physical_address = (u32)rsdt;
+
+    memcpy(rsdt, xsdt, sizeof(struct acpi_table_header));
+    rsdt->signature = RSDT_SIGNATURE;
+    rsdt->length = rsdt_size;
+    rsdt->revision = 1;
+    int j;
+    for (i=j=0; (void*)&xsdt->table_offset_entry[i] < end; i++) {
+        u64 tbl_addr = xsdt->table_offset_entry[i];
+        if (!tbl_addr || (tbl_addr & ~0xffffffffULL))
+            continue;
+        rsdt->table_offset_entry[j++] = (u32)tbl_addr;
+    }
+
+    rsdt->checksum -= checksum(rsdt, rsdt_size);
+}
+
 void
 qemu_platform_setup(void)
 {
@@ -186,8 +227,10 @@ qemu_platform_setup(void)
 
         RsdpAddr = find_acpi_rsdp();
 
-        if (RsdpAddr)
+        if (RsdpAddr) {
+            build_compatibility_rsdt();
             return;
+        }
 
         /* If present, loader should have installed an RSDP.
          * Not installed? We might still be able to continue
diff --git a/src/std/acpi.h b/src/std/acpi.h
index c2ea707..caf5e7e 100644
--- a/src/std/acpi.h
+++ b/src/std/acpi.h
@@ -133,6 +133,17 @@ struct rsdt_descriptor_rev1
 } PACKED;
 
 /*
+ * ACPI 2.0 Root System Description Table (RSDT)
+ */
+#define XSDT_SIGNATURE 0x54445358 // RSDT
+struct xsdt_descriptor_rev1
+{
+    ACPI_TABLE_HEADER_DEF       /* ACPI common table header */
+    u64 table_offset_entry[0];  /* Array of pointers to other */
+    /* ACPI tables */
+} PACKED;
+
+/*
  * ACPI 1.0 Firmware ACPI Control Structure (FACS)
  */
 #define FACS_SIGNATURE 0x53434146 // FACS
-- 
2.13.3


>From 46c7a296d27bd487cfd89a40973b1e61426dfbd0 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Tue, 25 Jul 2017 18:59:20 +0200
Subject: [PATCH 2/2] seabios: create v1 FADT in compatibility RSDT

This patch presents a v1 FADT inside the compatibility RSDT, so
that old operating systems are not broken.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 src/fw/paravirt.c | 18 +++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/src/fw/paravirt.c b/src/fw/paravirt.c
index 19a4abe..a9b9e80 100644
--- a/src/fw/paravirt.c
+++ b/src/fw/paravirt.c
@@ -148,6 +148,18 @@ static void msr_feature_control_setup(void)
         wrmsr_smp(MSR_IA32_FEATURE_CONTROL, feature_control_bits);
 }
 
+static void*
+build_rev1_fadt(struct fadt_descriptor_rev1 *fadt_v3)
+{
+    struct fadt_descriptor_rev1 *fadt_v1 = malloc_high(sizeof *fadt_v1);
+
+    memcpy(fadt_v1, fadt_v3, sizeof *fadt_v1);
+    fadt_v1->length = sizeof *fadt_v1;
+    fadt_v1->revision = 1;
+    fadt_v1->checksum -= checksum(fadt_v1, fadt_v1->length);
+    return fadt_v1;
+}
+
 static void
 build_compatibility_rsdt(void)
 {
@@ -182,6 +194,12 @@ build_compatibility_rsdt(void)
         u64 tbl_addr = xsdt->table_offset_entry[i];
         if (!tbl_addr || (tbl_addr & ~0xffffffffULL))
             continue;
+        struct acpi_table_header *tbl = (void*)(u32)tbl_addr;
+        /* The RSDT should only have an ACPI 1.0 FADT according to
+         * the spec.
+         */
+        if (tbl->signature == FACP_SIGNATURE && tbl->revision > 1)
+            tbl_addr = (u32)build_rev1_fadt((void *)tbl);
         rsdt->table_offset_entry[j++] = (u32)tbl_addr;
     }
 
-- 
2.13.3