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Diffstat (limited to 'classification_output/02/other/66743673')
| -rw-r--r-- | classification_output/02/other/66743673 | 365 |
1 files changed, 0 insertions, 365 deletions
diff --git a/classification_output/02/other/66743673 b/classification_output/02/other/66743673 deleted file mode 100644 index dffa1fc10..000000000 --- a/classification_output/02/other/66743673 +++ /dev/null @@ -1,365 +0,0 @@ -other: 0.967 -semantic: 0.951 -boot: 0.938 -instruction: 0.930 -mistranslation: 0.855 - -[Bug] QEMU TCG warnings after commit c6bd2dd63420 - HTT / CMP_LEG bits - -Hi Community, - -This email contains 3 bugs appear to share the same root cause. - -[1] We ran into the following warnings when running QEMU v10.0.0 in TCG mode: - -qemu-system-x86_64 \ - -machine q35 \ - -m 4G -smp 4 \ - -kernel ./arch/x86/boot/bzImage \ - -bios /usr/share/ovmf/OVMF.fd \ - -drive file=~/kernel/rootfs.ext4,index=0,format=raw,media=disk \ - -drive file=~/kernel/swap.img,index=1,format=raw,media=disk \ - -nographic \ - -append 'root=/dev/sda rw resume=/dev/sdb console=ttyS0 nokaslr' -qemu-system-x86_64: warning: TCG doesn't support requested feature: -CPUID.01H:EDX.ht [bit 28] -qemu-system-x86_64: warning: TCG doesn't support requested feature: -CPUID.80000001H:ECX.cmp-legacy [bit 1] -(repeats 4 times, once per vCPU) -Tracing the history shows that commit c6bd2dd63420 "i386/cpu: Set up CPUID_HT in -x86_cpu_expand_features() instead of cpu_x86_cpuid()" is what introduced the -warnings. -Since that commit, TCG unconditionally advertises HTT (CPUID 1 EDX[28]) and -CMP_LEG (CPUID 8000_0001 ECX[1]). Because TCG itself has no SMT support, these -bits trigger the warnings above. -[2] Also, Zhao pointed me to a similar report on GitLab: -https://gitlab.com/qemu-project/qemu/-/issues/2894 -The symptoms there look identical to what we're seeing. -By convention we file one issue per email, but these two appear to share the -same root cause, so I'm describing them together here. -[3] My colleague Alan noticed what appears to be a related problem: if we launch -a guest with '-cpu <model>,-ht --enable-kvm', which means explicitly removing -the ht flag, but the guest still reports HT(cat /proc/cpuinfo in linux guest) -enabled. In other words, under KVM the ht bit seems to be forced on even when -the user tries to disable it. -Best regards, -Ewan - -On 4/29/25 11:02 AM, Ewan Hai wrote: -Hi Community, - -This email contains 3 bugs appear to share the same root cause. - -[1] We ran into the following warnings when running QEMU v10.0.0 in TCG mode: - -qemu-system-x86_64 \ - Â -machine q35 \ - Â -m 4G -smp 4 \ - Â -kernel ./arch/x86/boot/bzImage \ - Â -bios /usr/share/ovmf/OVMF.fd \ - Â -drive file=~/kernel/rootfs.ext4,index=0,format=raw,media=disk \ - Â -drive file=~/kernel/swap.img,index=1,format=raw,media=disk \ - Â -nographic \ - Â -append 'root=/dev/sda rw resume=/dev/sdb console=ttyS0 nokaslr' -qemu-system-x86_64: warning: TCG doesn't support requested feature: -CPUID.01H:EDX.ht [bit 28] -qemu-system-x86_64: warning: TCG doesn't support requested feature: -CPUID.80000001H:ECX.cmp-legacy [bit 1] -(repeats 4 times, once per vCPU) -Tracing the history shows that commit c6bd2dd63420 "i386/cpu: Set up CPUID_HT in -x86_cpu_expand_features() instead of cpu_x86_cpuid()" is what introduced the -warnings. -Since that commit, TCG unconditionally advertises HTT (CPUID 1 EDX[28]) and -CMP_LEG (CPUID 8000_0001 ECX[1]). Because TCG itself has no SMT support, these -bits trigger the warnings above. -[2] Also, Zhao pointed me to a similar report on GitLab: -https://gitlab.com/qemu-project/qemu/-/issues/2894 -The symptoms there look identical to what we're seeing. -By convention we file one issue per email, but these two appear to share the -same root cause, so I'm describing them together here. -[3] My colleague Alan noticed what appears to be a related problem: if we launch -a guest with '-cpu <model>,-ht --enable-kvm', which means explicitly removing -the ht flag, but the guest still reports HT(cat /proc/cpuinfo in linux guest) -enabled. In other words, under KVM the ht bit seems to be forced on even when -the user tries to disable it. -XiaoYao reminded me that issue [3] stems from a different patch. Please ignore -it for nowâI'll start a separate thread to discuss that one independently. -Best regards, -Ewan - -On 4/29/2025 11:02 AM, Ewan Hai wrote: -Hi Community, - -This email contains 3 bugs appear to share the same root cause. -[1] We ran into the following warnings when running QEMU v10.0.0 in TCG -mode: -qemu-system-x86_64 \ - Â -machine q35 \ - Â -m 4G -smp 4 \ - Â -kernel ./arch/x86/boot/bzImage \ - Â -bios /usr/share/ovmf/OVMF.fd \ - Â -drive file=~/kernel/rootfs.ext4,index=0,format=raw,media=disk \ - Â -drive file=~/kernel/swap.img,index=1,format=raw,media=disk \ - Â -nographic \ - Â -append 'root=/dev/sda rw resume=/dev/sdb console=ttyS0 nokaslr' -qemu-system-x86_64: warning: TCG doesn't support requested feature: -CPUID.01H:EDX.ht [bit 28] -qemu-system-x86_64: warning: TCG doesn't support requested feature: -CPUID.80000001H:ECX.cmp-legacy [bit 1] -(repeats 4 times, once per vCPU) -Tracing the history shows that commit c6bd2dd63420 "i386/cpu: Set up -CPUID_HT in x86_cpu_expand_features() instead of cpu_x86_cpuid()" is -what introduced the warnings. -Since that commit, TCG unconditionally advertises HTT (CPUID 1 EDX[28]) -and CMP_LEG (CPUID 8000_0001 ECX[1]). Because TCG itself has no SMT -support, these bits trigger the warnings above. -[2] Also, Zhao pointed me to a similar report on GitLab: -https://gitlab.com/qemu-project/qemu/-/issues/2894 -The symptoms there look identical to what we're seeing. -By convention we file one issue per email, but these two appear to share -the same root cause, so I'm describing them together here. -It was caused by my two patches. I think the fix can be as follow. -If no objection from the community, I can submit the formal patch. - -diff --git a/target/i386/cpu.c b/target/i386/cpu.c -index 1f970aa4daa6..fb95aadd6161 100644 ---- a/target/i386/cpu.c -+++ b/target/i386/cpu.c -@@ -776,11 +776,12 @@ void x86_cpu_vendor_words2str(char *dst, uint32_t -vendor1, -CPUID_PAE | CPUID_MCE | CPUID_CX8 | CPUID_APIC | CPUID_SEP | \ - CPUID_MTRR | CPUID_PGE | CPUID_MCA | CPUID_CMOV | CPUID_PAT | \ - CPUID_PSE36 | CPUID_CLFLUSH | CPUID_ACPI | CPUID_MMX | \ -- CPUID_FXSR | CPUID_SSE | CPUID_SSE2 | CPUID_SS | CPUID_DE) -+ CPUID_FXSR | CPUID_SSE | CPUID_SSE2 | CPUID_SS | CPUID_DE | \ -+ CPUID_HT) - /* partly implemented: - CPUID_MTRR, CPUID_MCA, CPUID_CLFLUSH (needed for Win64) */ - /* missing: -- CPUID_VME, CPUID_DTS, CPUID_SS, CPUID_HT, CPUID_TM, CPUID_PBE */ -+ CPUID_VME, CPUID_DTS, CPUID_SS, CPUID_TM, CPUID_PBE */ - - /* - * Kernel-only features that can be shown to usermode programs even if -@@ -848,7 +849,8 @@ void x86_cpu_vendor_words2str(char *dst, uint32_t -vendor1, -#define TCG_EXT3_FEATURES (CPUID_EXT3_LAHF_LM | CPUID_EXT3_SVM | \ - CPUID_EXT3_CR8LEG | CPUID_EXT3_ABM | CPUID_EXT3_SSE4A | \ -- CPUID_EXT3_3DNOWPREFETCH | CPUID_EXT3_KERNEL_FEATURES) -+ CPUID_EXT3_3DNOWPREFETCH | CPUID_EXT3_KERNEL_FEATURES | \ -+ CPUID_EXT3_CMP_LEG) - - #define TCG_EXT4_FEATURES 0 -[3] My colleague Alan noticed what appears to be a related problem: if -we launch a guest with '-cpu <model>,-ht --enable-kvm', which means -explicitly removing the ht flag, but the guest still reports HT(cat / -proc/cpuinfo in linux guest) enabled. In other words, under KVM the ht -bit seems to be forced on even when the user tries to disable it. -This has been the behavior of QEMU for many years, not some regression -introduced by my patches. We can discuss how to address it separately. -Best regards, -Ewan - -On Tue, Apr 29, 2025 at 01:55:59PM +0800, Xiaoyao Li wrote: -> -Date: Tue, 29 Apr 2025 13:55:59 +0800 -> -From: Xiaoyao Li <xiaoyao.li@intel.com> -> -Subject: Re: [Bug] QEMU TCG warnings after commit c6bd2dd63420 - HTT / -> -CMP_LEG bits -> -> -On 4/29/2025 11:02 AM, Ewan Hai wrote: -> -> Hi Community, -> -> -> -> This email contains 3 bugs appear to share the same root cause. -> -> -> -> [1] We ran into the following warnings when running QEMU v10.0.0 in TCG -> -> mode: -> -> -> -> qemu-system-x86_64 \ -> -> Â -machine q35 \ -> -> Â -m 4G -smp 4 \ -> -> Â -kernel ./arch/x86/boot/bzImage \ -> -> Â -bios /usr/share/ovmf/OVMF.fd \ -> -> Â -drive file=~/kernel/rootfs.ext4,index=0,format=raw,media=disk \ -> -> Â -drive file=~/kernel/swap.img,index=1,format=raw,media=disk \ -> -> Â -nographic \ -> -> Â -append 'root=/dev/sda rw resume=/dev/sdb console=ttyS0 nokaslr' -> -> -> -> qemu-system-x86_64: warning: TCG doesn't support requested feature: -> -> CPUID.01H:EDX.ht [bit 28] -> -> qemu-system-x86_64: warning: TCG doesn't support requested feature: -> -> CPUID.80000001H:ECX.cmp-legacy [bit 1] -> -> (repeats 4 times, once per vCPU) -> -> -> -> Tracing the history shows that commit c6bd2dd63420 "i386/cpu: Set up -> -> CPUID_HT in x86_cpu_expand_features() instead of cpu_x86_cpuid()" is -> -> what introduced the warnings. -> -> -> -> Since that commit, TCG unconditionally advertises HTT (CPUID 1 EDX[28]) -> -> and CMP_LEG (CPUID 8000_0001 ECX[1]). Because TCG itself has no SMT -> -> support, these bits trigger the warnings above. -> -> -> -> [2] Also, Zhao pointed me to a similar report on GitLab: -> -> -https://gitlab.com/qemu-project/qemu/-/issues/2894 -> -> The symptoms there look identical to what we're seeing. -> -> -> -> By convention we file one issue per email, but these two appear to share -> -> the same root cause, so I'm describing them together here. -> -> -It was caused by my two patches. I think the fix can be as follow. -> -If no objection from the community, I can submit the formal patch. -> -> -diff --git a/target/i386/cpu.c b/target/i386/cpu.c -> -index 1f970aa4daa6..fb95aadd6161 100644 -> ---- a/target/i386/cpu.c -> -+++ b/target/i386/cpu.c -> -@@ -776,11 +776,12 @@ void x86_cpu_vendor_words2str(char *dst, uint32_t -> -vendor1, -> -CPUID_PAE | CPUID_MCE | CPUID_CX8 | CPUID_APIC | CPUID_SEP | \ -> -CPUID_MTRR | CPUID_PGE | CPUID_MCA | CPUID_CMOV | CPUID_PAT | \ -> -CPUID_PSE36 | CPUID_CLFLUSH | CPUID_ACPI | CPUID_MMX | \ -> -- CPUID_FXSR | CPUID_SSE | CPUID_SSE2 | CPUID_SS | CPUID_DE) -> -+ CPUID_FXSR | CPUID_SSE | CPUID_SSE2 | CPUID_SS | CPUID_DE | \ -> -+ CPUID_HT) -> -/* partly implemented: -> -CPUID_MTRR, CPUID_MCA, CPUID_CLFLUSH (needed for Win64) */ -> -/* missing: -> -- CPUID_VME, CPUID_DTS, CPUID_SS, CPUID_HT, CPUID_TM, CPUID_PBE */ -> -+ CPUID_VME, CPUID_DTS, CPUID_SS, CPUID_TM, CPUID_PBE */ -> -> -/* -> -* Kernel-only features that can be shown to usermode programs even if -> -@@ -848,7 +849,8 @@ void x86_cpu_vendor_words2str(char *dst, uint32_t -> -vendor1, -> -> -#define TCG_EXT3_FEATURES (CPUID_EXT3_LAHF_LM | CPUID_EXT3_SVM | \ -> -CPUID_EXT3_CR8LEG | CPUID_EXT3_ABM | CPUID_EXT3_SSE4A | \ -> -- CPUID_EXT3_3DNOWPREFETCH | CPUID_EXT3_KERNEL_FEATURES) -> -+ CPUID_EXT3_3DNOWPREFETCH | CPUID_EXT3_KERNEL_FEATURES | \ -> -+ CPUID_EXT3_CMP_LEG) -> -> -#define TCG_EXT4_FEATURES 0 -This fix is fine for me...at least from SDM, HTT depends on topology and -it should exist when user sets "-smp 4". - -> -> [3] My colleague Alan noticed what appears to be a related problem: if -> -> we launch a guest with '-cpu <model>,-ht --enable-kvm', which means -> -> explicitly removing the ht flag, but the guest still reports HT(cat -> -> /proc/cpuinfo in linux guest) enabled. In other words, under KVM the ht -> -> bit seems to be forced on even when the user tries to disable it. -> -> -XiaoYao reminded me that issue [3] stems from a different patch. Please -> -ignore it for nowâI'll start a separate thread to discuss that one -> -independently. -I haven't found any other thread :-). - -By the way, just curious, in what cases do you need to disbale the HT -flag? "-smp 4" means 4 cores with 1 thread per core, and is it not -enough? - -As for the â-htâ behavior, I'm also unsure whether this should be fixed -or not - one possible consideration is whether â-htâ would be useful. - -On 5/8/25 5:04 PM, Zhao Liu wrote: -[3] My colleague Alan noticed what appears to be a related problem: if -we launch a guest with '-cpu <model>,-ht --enable-kvm', which means -explicitly removing the ht flag, but the guest still reports HT(cat -/proc/cpuinfo in linux guest) enabled. In other words, under KVM the ht -bit seems to be forced on even when the user tries to disable it. -XiaoYao reminded me that issue [3] stems from a different patch. Please -ignore it for nowâI'll start a separate thread to discuss that one -independently. -I haven't found any other thread :-). -Please refer to -https://lore.kernel.org/all/db6ae3bb-f4e5-4719-9beb-623fcff56af2@zhaoxin.com/ -. -By the way, just curious, in what cases do you need to disbale the HT -flag? "-smp 4" means 4 cores with 1 thread per core, and is it not -enough? - -As for the â-htâ behavior, I'm also unsure whether this should be fixed -or not - one possible consideration is whether â-htâ would be useful. -I wasn't trying to target any specific use case, using "-ht" was simply a way to -check how the ht feature behaves under both KVM and TCG. There's no special -workload behind it; I just wanted to confirm that the flag is respected (or not) -in each mode. - |