From: myrslint <[email protected]> On x86_64, where most CPUs support self-snoop, it is preferrable to always honor guest PAT. Not doing so is a quirk. There is a default enabled KVM quirk flag which enforces not doing so due to a former bug in Bochs display driver.
The bug has been fixed but not enough has yet passed since so we only disable said quirk flag if a Bochs display is not configured for the virtual machine. This commit also moves around a bit of code that would be called when the initialization of a VM is done. Signed-off-by: Myrsky Lintu <[email protected]> Reviewed-by: Dmitry Osipenko <[email protected]> Tested-by: Dmitry Osipenko <[email protected]> # intel-ivb --- accel/kvm/kvm-all.c | 1 + accel/stubs/kvm-stub.c | 1 + hw/display/bochs-display.c | 17 +++++++++++++++ include/system/kvm.h | 9 ++++++++ target/i386/kvm/kvm.c | 42 +++++++++++++++++++++++++++++++------- 5 files changed, 63 insertions(+), 7 deletions(-) diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c index f9254ae654..36a12593ee 100644 --- a/accel/kvm/kvm-all.c +++ b/accel/kvm/kvm-all.c @@ -103,6 +103,7 @@ bool kvm_readonly_mem_allowed; bool kvm_vm_attributes_allowed; bool kvm_msi_use_devid; bool kvm_pre_fault_memory_supported; +bool kvm_bochs_drm_quirk; static bool kvm_has_guest_debug; static int kvm_sstep_flags; static bool kvm_immediate_exit; diff --git a/accel/stubs/kvm-stub.c b/accel/stubs/kvm-stub.c index 68cd33ba97..a69c89e1ad 100644 --- a/accel/stubs/kvm-stub.c +++ b/accel/stubs/kvm-stub.c @@ -24,6 +24,7 @@ bool kvm_gsi_direct_mapping; bool kvm_allowed; bool kvm_readonly_mem_allowed; bool kvm_msi_use_devid; +bool kvm_bochs_drm_quirk; void kvm_flush_coalesced_mmio_buffer(void) { diff --git a/hw/display/bochs-display.c b/hw/display/bochs-display.c index ad2821c974..e8def68b41 100644 --- a/hw/display/bochs-display.c +++ b/hw/display/bochs-display.c @@ -20,6 +20,8 @@ #include "ui/qemu-pixman.h" #include "qom/object.h" +#include "system/kvm.h" + typedef struct BochsDisplayMode { pixman_format_code_t format; uint32_t bytepp; @@ -309,6 +311,21 @@ static void bochs_display_realize(PCIDevice *dev, Error **errp) } memory_region_set_log(&s->vram, true, DIRTY_MEMORY_VGA); + + /* + * On x86_64, where most CPUs support self-snoop, it is preferrable to + * always honor guest PAT. Not doing so is a quirk. There is a default + * enabled KVM quirk flag which enforces not doing so due to a former bug + * in Bochs display driver. + * + * The bug has been fixed but not enough has yet passed since so we only + * disable said quirk flag if a Bochs display is not configured for the + * virtual machine. + * + * The following flag tells KVM initialization code not to disable that + * quirk flag. + */ + kvm_bochs_drm_quirk = true; } static bool bochs_display_get_big_endian_fb(Object *obj, Error **errp) diff --git a/include/system/kvm.h b/include/system/kvm.h index 8f9eecf044..123016777c 100644 --- a/include/system/kvm.h +++ b/include/system/kvm.h @@ -43,6 +43,7 @@ extern bool kvm_gsi_direct_mapping; extern bool kvm_readonly_mem_allowed; extern bool kvm_msi_use_devid; extern bool kvm_pre_fault_memory_supported; +extern bool kvm_bochs_drm_quirk; #define kvm_enabled() (kvm_allowed) /** @@ -144,6 +145,13 @@ extern bool kvm_pre_fault_memory_supported; */ #define kvm_msi_devid_required() (kvm_msi_use_devid) +/** + * kvm_has_bochs_drm: + * Returns: true if KVM is possible and a Bochs DRM driver is + * in use for display. + */ +#define kvm_has_bochs_drm() (kvm_bochs_drm_quirk) + #else #define kvm_enabled() (0) @@ -158,6 +166,7 @@ extern bool kvm_pre_fault_memory_supported; #define kvm_gsi_direct_mapping() (false) #define kvm_readonly_mem_enabled() (false) #define kvm_msi_devid_required() (false) +#define kvm_has_bochs_drm() (false) #endif /* CONFIG_KVM_IS_POSSIBLE */ diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c index 60c7981138..dd2594f5af 100644 --- a/target/i386/kvm/kvm.c +++ b/target/i386/kvm/kvm.c @@ -2709,13 +2709,13 @@ static bool kvm_rdmsr_pkg_energy_status(X86CPU *cpu, return true; } -static Notifier smram_machine_done; +static Notifier kvm_machine_done; static KVMMemoryListener smram_listener; static AddressSpace smram_address_space; static MemoryRegion smram_as_root; static MemoryRegion smram_as_mem; -static void register_smram_listener(Notifier *n, void *unused) +static void register_smram_listener(void) { CPUState *cpu; MemoryRegion *smram = @@ -2754,6 +2754,37 @@ void kvm_smm_cpu_address_space_init(X86CPU *cpu) cpu_address_space_init(CPU(cpu), X86ASIdx_SMM, "cpu-smm", &smram_as_root); } +static bool kvm_x86_smm_enabled(void) +{ + return object_dynamic_cast(OBJECT(current_machine), TYPE_X86_MACHINE) && + x86_machine_is_smm_enabled(X86_MACHINE(current_machine)); +} + +static int kvm_x86_disable_quirsk2_mask(void) +{ + return kvm_check_extension(kvm_state, KVM_CAP_DISABLE_QUIRKS2); +} + +static int kvm_disable_ignore_guest_pat(void) +{ + return kvm_vm_enable_cap(kvm_state, KVM_CAP_DISABLE_QUIRKS2, 0, \ + KVM_X86_QUIRK_IGNORE_GUEST_PAT); +} + +static void handle_machine_done(Notifier *n, void *unused) +{ + if (kvm_x86_smm_enabled()) { + register_smram_listener(); + } + if (!kvm_has_bochs_drm() && \ + (kvm_x86_disable_quirsk2_mask() & KVM_X86_QUIRK_IGNORE_GUEST_PAT)) { + if (kvm_disable_ignore_guest_pat()) { + error_report("KVM_X86_QUIRK_IGNORE_GUEST_PAT available and " + "modifiable but we failed to disable it"); + } + } +} + static void *kvm_msr_energy_thread(void *data) { KVMState *s = data; @@ -3334,11 +3365,8 @@ int kvm_arch_init(MachineState *ms, KVMState *s) return ret; } - if (object_dynamic_cast(OBJECT(ms), TYPE_X86_MACHINE) && - x86_machine_is_smm_enabled(X86_MACHINE(ms))) { - smram_machine_done.notify = register_smram_listener; - qemu_add_machine_init_done_notifier(&smram_machine_done); - } + kvm_machine_done.notify = handle_machine_done; + qemu_add_machine_init_done_notifier(&kvm_machine_done); if (enable_cpu_pm) { ret = kvm_vm_enable_disable_exits(s); -- 2.49.1
