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[PULL 03/27] target/i386: do not consult nonexistent host leaves
From: |
Paolo Bonzini |
Subject: |
[PULL 03/27] target/i386: do not consult nonexistent host leaves |
Date: |
Thu, 12 May 2022 19:24:41 +0200 |
When cache_info_passthrough is requested, QEMU passes the host values
of the cache information CPUID leaves down to the guest. However,
it blindly assumes that the CPUID leaf exists on the host, and this
cannot be guaranteed: for example, KVM has recently started to
synthesize AMD leaves up to 0x80000021 in order to provide accurate
CPU bug information to guests.
Querying a nonexistent host leaf fills the output arguments of
host_cpuid with data that (albeit deterministic) is nonsensical
as cache information, namely the data in the highest Intel CPUID
leaf. If said highest leaf is not ECX-dependent, this can even
cause an infinite loop when kvm_arch_init_vcpu prepares the input
to KVM_SET_CPUID2. The infinite loop is only terminated by an
abort() when the array gets full.
Reported-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
target/i386/cpu.c | 41 ++++++++++++++++++++++++++++++++++++-----
1 file changed, 36 insertions(+), 5 deletions(-)
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 62c240fa91..c4a17c93f6 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -5022,6 +5022,37 @@ uint64_t x86_cpu_get_supported_feature_word(FeatureWord
w,
return r;
}
+static void x86_cpu_get_cache_cpuid(uint32_t func, uint32_t index,
+ uint32_t *eax, uint32_t *ebx,
+ uint32_t *ecx, uint32_t *edx)
+{
+ uint32_t level, unused;
+
+ /* Only return valid host leaves. */
+ switch (func) {
+ case 2:
+ case 4:
+ host_cpuid(0, 0, &level, &unused, &unused, &unused);
+ break;
+ case 0x80000005:
+ case 0x80000006:
+ case 0x8000001d:
+ host_cpuid(0x80000000, 0, &level, &unused, &unused, &unused);
+ break;
+ default:
+ return;
+ }
+
+ if (func > level) {
+ *eax = 0;
+ *ebx = 0;
+ *ecx = 0;
+ *edx = 0;
+ } else {
+ host_cpuid(func, index, eax, ebx, ecx, edx);
+ }
+}
+
/*
* Only for builtin_x86_defs models initialized with x86_register_cpudef_types.
*/
@@ -5280,7 +5311,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index,
uint32_t count,
case 2:
/* cache info: needed for Pentium Pro compatibility */
if (cpu->cache_info_passthrough) {
- host_cpuid(index, 0, eax, ebx, ecx, edx);
+ x86_cpu_get_cache_cpuid(index, 0, eax, ebx, ecx, edx);
break;
} else if (cpu->vendor_cpuid_only && IS_AMD_CPU(env)) {
*eax = *ebx = *ecx = *edx = 0;
@@ -5300,7 +5331,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index,
uint32_t count,
case 4:
/* cache info: needed for Core compatibility */
if (cpu->cache_info_passthrough) {
- host_cpuid(index, count, eax, ebx, ecx, edx);
+ x86_cpu_get_cache_cpuid(index, count, eax, ebx, ecx, edx);
/* QEMU gives out its own APIC IDs, never pass down bits 31..26.
*/
*eax &= ~0xFC000000;
if ((*eax & 31) && cs->nr_cores > 1) {
@@ -5702,7 +5733,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index,
uint32_t count,
case 0x80000005:
/* cache info (L1 cache) */
if (cpu->cache_info_passthrough) {
- host_cpuid(index, 0, eax, ebx, ecx, edx);
+ x86_cpu_get_cache_cpuid(index, 0, eax, ebx, ecx, edx);
break;
}
*eax = (L1_DTLB_2M_ASSOC << 24) | (L1_DTLB_2M_ENTRIES << 16) |
@@ -5715,7 +5746,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index,
uint32_t count,
case 0x80000006:
/* cache info (L2 cache) */
if (cpu->cache_info_passthrough) {
- host_cpuid(index, 0, eax, ebx, ecx, edx);
+ x86_cpu_get_cache_cpuid(index, 0, eax, ebx, ecx, edx);
break;
}
*eax = (AMD_ENC_ASSOC(L2_DTLB_2M_ASSOC) << 28) |
@@ -5775,7 +5806,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index,
uint32_t count,
case 0x8000001D:
*eax = 0;
if (cpu->cache_info_passthrough) {
- host_cpuid(index, count, eax, ebx, ecx, edx);
+ x86_cpu_get_cache_cpuid(index, count, eax, ebx, ecx, edx);
break;
}
switch (count) {
--
2.36.0
- [PULL 00/27] Misc patches for 2022-05-12, Paolo Bonzini, 2022/05/12
- [PULL 02/27] pc-bios/optionrom: compile with -Wno-array-bounds, Paolo Bonzini, 2022/05/12
- [PULL 03/27] target/i386: do not consult nonexistent host leaves,
Paolo Bonzini <=
- [PULL 01/27] pc-bios/optionrom: detect -fno-pie, Paolo Bonzini, 2022/05/12
- [PULL 05/27] meson: Make mremap() detecting works correctly, Paolo Bonzini, 2022/05/12
- [PULL 11/27] machine: use QAPI struct for boot configuration, Paolo Bonzini, 2022/05/12
- [PULL 12/27] machine: add boot compound property, Paolo Bonzini, 2022/05/12
- [PULL 16/27] slirp: bump submodule past 4.7 release, Paolo Bonzini, 2022/05/12
- [PULL 06/27] hw/xen/xen_pt: Confine igd-passthrough-isa-bridge to XEN, Paolo Bonzini, 2022/05/12
- [PULL 14/27] machine: make memory-backend a link property, Paolo Bonzini, 2022/05/12
- [PULL 17/27] net: slirp: introduce a wrapper struct for QemuTimer, Paolo Bonzini, 2022/05/12
- [PULL 18/27] net: slirp: switch to slirp_new, Paolo Bonzini, 2022/05/12
- [PULL 20/27] net: slirp: allow CFI with libslirp >= 4.7, Paolo Bonzini, 2022/05/12