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kvm/i386: replace identity_base variable with a constant

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identity_base variable is first initialzied to address 0xfffbc000 and then
kvm_vm_set_identity_map_addr() overrides this value to address 0xfeffc000.
The initial address to which the variable was initialized was never used. Clean
everything up, placing 0xfeffc000 in a preprocessor constant.

Reported-by: Ani Sinha <anisinha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2024-09-04 14:29:00 +02:00
parent 0cc42e63bb
commit dc44854978
1 changed files with 18 additions and 18 deletions
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36
target/i386/kvm/kvm.c
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@ -81,6 +81,16 @@
do { } while (0) do { } while (0)
#endif #endif
/*
* On older Intel CPUs, KVM uses vm86 mode to emulate 16-bit code directly.
* In order to use vm86 mode, an EPT identity map and a TSS are needed.
* Since these must be part of guest physical memory, we need to allocate
* them, both by setting their start addresses in the kernel and by
* creating a corresponding e820 entry. We need 4 pages before the BIOS,
* so this value allows up to 16M BIOSes.
*/
#define KVM_IDENTITY_BASE 0xfeffc000
/* From arch/x86/kvm/lapic.h */ /* From arch/x86/kvm/lapic.h */
#define KVM_APIC_BUS_CYCLE_NS 1 #define KVM_APIC_BUS_CYCLE_NS 1
#define KVM_APIC_BUS_FREQUENCY (1000000000ULL / KVM_APIC_BUS_CYCLE_NS) #define KVM_APIC_BUS_FREQUENCY (1000000000ULL / KVM_APIC_BUS_CYCLE_NS)
@ -3036,18 +3046,9 @@ static int kvm_vm_enable_triple_fault_event(KVMState *s)
return ret; return ret;
} }
static int kvm_vm_set_identity_map_addr(KVMState *s, uint64_t *identity_base) static int kvm_vm_set_identity_map_addr(KVMState *s, uint64_t identity_base)
{ {
/* return kvm_vm_ioctl(s, KVM_SET_IDENTITY_MAP_ADDR, &identity_base);
* On older Intel CPUs, KVM uses vm86 mode to emulate 16-bit code directly.
* In order to use vm86 mode, an EPT identity map and a TSS are needed.
* Since these must be part of guest physical memory, we need to allocate
* them, both by setting their start addresses in the kernel and by
* creating a corresponding e820 entry. We need 4 pages before the BIOS,
* so this value allows up to 16M BIOSes.
*/
*identity_base = 0xfeffc000;
return kvm_vm_ioctl(s, KVM_SET_IDENTITY_MAP_ADDR, identity_base);
} }
static int kvm_vm_set_nr_mmu_pages(KVMState *s) static int kvm_vm_set_nr_mmu_pages(KVMState *s)
@ -3064,10 +3065,9 @@ static int kvm_vm_set_nr_mmu_pages(KVMState *s)
return ret; return ret;
} }
static int kvm_vm_set_tss_addr(KVMState *s, uint64_t identity_base) static int kvm_vm_set_tss_addr(KVMState *s, uint64_t tss_base)
{ {
/* Set TSS base one page after EPT identity map. */ return kvm_vm_ioctl(s, KVM_SET_TSS_ADDR, tss_base);
return kvm_vm_ioctl(s, KVM_SET_TSS_ADDR, identity_base);
} }
static int kvm_vm_enable_disable_exits(KVMState *s) static int kvm_vm_enable_disable_exits(KVMState *s)
@ -3183,7 +3183,6 @@ static void kvm_vm_enable_energy_msrs(KVMState *s)
int kvm_arch_init(MachineState *ms, KVMState *s) int kvm_arch_init(MachineState *ms, KVMState *s)
{ {
uint64_t identity_base = 0xfffbc000;
int ret; int ret;
struct utsname utsname; struct utsname utsname;
Error *local_err = NULL; Error *local_err = NULL;
@ -3251,18 +3250,19 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
uname(&utsname); uname(&utsname);
lm_capable_kernel = strcmp(utsname.machine, "x86_64") == 0; lm_capable_kernel = strcmp(utsname.machine, "x86_64") == 0;
ret = kvm_vm_set_identity_map_addr(s, &identity_base); ret = kvm_vm_set_identity_map_addr(s, KVM_IDENTITY_BASE);
if (ret < 0) { if (ret < 0) {
return ret; return ret;
} }
ret = kvm_vm_set_tss_addr(s, identity_base + 0x1000); /* Set TSS base one page after EPT identity map. */
ret = kvm_vm_set_tss_addr(s, KVM_IDENTITY_BASE + 0x1000);
if (ret < 0) { if (ret < 0) {
return ret; return ret;
} }
/* Tell fw_cfg to notify the BIOS to reserve the range. */ /* Tell fw_cfg to notify the BIOS to reserve the range. */
e820_add_entry(identity_base, 0x4000, E820_RESERVED); e820_add_entry(KVM_IDENTITY_BASE, 0x4000, E820_RESERVED);
ret = kvm_vm_set_nr_mmu_pages(s); ret = kvm_vm_set_nr_mmu_pages(s);
if (ret < 0) { if (ret < 0) {