hvmloader: limit CPUs exposed to guests

Various Linux versions allocate (partial) per-CPU data for all of them,
as there is no indication in MADT whether they're hotpluggable. That's
a little wasteful in terms of resource consumption especially for
- guests with not overly much memory assigned,
- 32-bit guests not having overly much address space available.
Therefore limit what we put into MADT to the "maxvcpus" value, and make
sure AML doesn't touch memory addresses corresponding to CPUs beyond
that value (we can't reasonably make the respective processor objects
disappear).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

diff --git a/tools/firmware/hvmloader/acpi/build.c b/tools/firmware/hvmloader/acpi/build.c
index 503648ce976fa688727c2ef63ee48ecddc4b52e5..1f7103eb6e13628765f7dd0a7d817365c35253c3 100644 (file)
--- a/tools/firmware/hvmloader/acpi/build.c
+++ b/tools/firmware/hvmloader/acpi/build.c
@@ -48,6 +48,7 @@ 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? */
+    uint16_t nr_cpus;           /* 2    - Number of CPUs */
     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 */
@@ -55,9 +56,6 @@ struct acpi_info {
     uint64_t pci_hi_min, pci_hi_len; /* 24, 32 - PCI I/O hole boundaries */
 };
 
-/* Number of processor objects in the chosen DSDT. */
-static unsigned int nr_processor_objects;
-
 static void set_checksum(
     void *table, uint32_t checksum_offset, uint32_t length)
 {
@@ -89,7 +87,7 @@ static struct acpi_20_madt *construct_madt(struct acpi_info *info)
     sz  = sizeof(struct acpi_20_madt);
     sz += sizeof(struct acpi_20_madt_intsrcovr) * 16;
     sz += sizeof(struct acpi_20_madt_ioapic);
-    sz += sizeof(struct acpi_20_madt_lapic) * nr_processor_objects;
+    sz += sizeof(struct acpi_20_madt_lapic) * hvm_info->nr_vcpus;
 
     madt = mem_alloc(sz, 16);
     if (!madt) return NULL;
@@ -142,8 +140,9 @@ static struct acpi_20_madt *construct_madt(struct acpi_info *info)
     io_apic->ioapic_addr = IOAPIC_BASE_ADDRESS;
 
     lapic = (struct acpi_20_madt_lapic *)(io_apic + 1);
+    info->nr_cpus = hvm_info->nr_vcpus;
     info->madt_lapic0_addr = (uint32_t)lapic;
-    for ( i = 0; i < nr_processor_objects; i++ )
+    for ( i = 0; i < hvm_info->nr_vcpus; i++ )
     {
         memset(lapic, 0, sizeof(*lapic));
         lapic->type    = ACPI_PROCESSOR_LOCAL_APIC;
@@ -151,8 +150,7 @@ static struct acpi_20_madt *construct_madt(struct acpi_info *info)
         /* Processor ID must match processor-object IDs in the DSDT. */
         lapic->acpi_processor_id = i;
         lapic->apic_id = LAPIC_ID(i);
-        lapic->flags = ((i < hvm_info->nr_vcpus) &&
-                        test_bit(i, hvm_info->vcpu_online)
+        lapic->flags = (test_bit(i, hvm_info->vcpu_online)
                         ? ACPI_LOCAL_APIC_ENABLED : 0);
         lapic++;
     }
@@ -534,14 +532,12 @@ void acpi_build_tables(struct acpi_config *config, unsigned int physical)
         dsdt = mem_alloc(config->dsdt_15cpu_len, 16);
         if (!dsdt) goto oom;
         memcpy(dsdt, config->dsdt_15cpu, config->dsdt_15cpu_len);
-        nr_processor_objects = 15;
     }
     else
     {
         dsdt = mem_alloc(config->dsdt_anycpu_len, 16);
         if (!dsdt) goto oom;
         memcpy(dsdt, config->dsdt_anycpu, config->dsdt_anycpu_len);
-        nr_processor_objects = HVM_MAX_VCPUS;
     }
 
     /*

diff --git a/tools/firmware/hvmloader/acpi/dsdt.asl b/tools/firmware/hvmloader/acpi/dsdt.asl
index e266dc2fcd036859d70d66df95dfb5a77794e1a8..bd65823697aa8ce9be0f838e4f02c98b25824a53 100644 (file)
--- a/tools/firmware/hvmloader/acpi/dsdt.asl
+++ b/tools/firmware/hvmloader/acpi/dsdt.asl
@@ -50,7 +50,8 @@ DefinitionBlock ("DSDT.aml", "DSDT", 2, "Xen", "HVM", 0)
            UAR2, 1,
            LTP1, 1,
            HPET, 1,
-           Offset(4),
+           Offset(2),
+           NCPU, 16,
            PMIN, 32,
            PLEN, 32,
            MSUA, 32, /* MADT checksum address */

diff --git a/tools/firmware/hvmloader/acpi/mk_dsdt.c b/tools/firmware/hvmloader/acpi/mk_dsdt.c
index b567b38063c85a842b07f624cd46fd9fe9160e86..b2ade89674906ce8bcaf86de6761dc96ab799e88 100644 (file)
--- a/tools/firmware/hvmloader/acpi/mk_dsdt.c
+++ b/tools/firmware/hvmloader/acpi/mk_dsdt.c
@@ -150,6 +150,14 @@ int main(int argc, char **argv)
     indent(); printf("MSU, 8\n");
     pop_block();
 
+    /* Processor object helpers. */
+    push_block("Method", "PMAT, 2");
+    push_block("If", "LLess(Arg0, NCPU)");
+    stmt("Return", "ToBuffer(Arg1)");
+    pop_block();
+    stmt("Return", "Buffer() {0, 8, 0xff, 0xff, 0, 0, 0, 0}");
+    pop_block();
+
     /* Define processor objects and control methods. */
     for ( cpu = 0; cpu < max_cpus; cpu++)
     {
@@ -171,17 +179,22 @@ int main(int argc, char **argv)
         pop_block();
 
         push_block("Method", "_MAT, 0");
-        stmt("Return", "ToBuffer(MAT)");
+        if ( cpu )
+            stmt("Return", "PMAT (%d, MAT)", cpu);
+        else
+            stmt("Return", "ToBuffer(MAT)");
         pop_block();
 
         push_block("Method", "_STA");
+        if ( cpu )
+            push_block("If", "LLess(%d, \\_SB.NCPU)", cpu);
         push_block("If", "FLG");
         stmt("Return", "0xF");
         pop_block();
-        push_block("Else", NULL);
+        if ( cpu )
+            pop_block();
         stmt("Return", "0x0");
         pop_block();
-        pop_block();
 
         push_block("Method", "_EJ0, 1, NotSerialized");
         stmt("Sleep", "0xC8");