| Message ID | 20210818114956.7171-1-pmenzel@molgen.mpg.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | x86: kvm: Demote level of already loaded message from error to info | expand |
On 18.08.2021 13:49, Paul Menzel wrote: > In scripts, running > > modprobe kvm_amd 2>/dev/null > modprobe kvm_intel 2>/dev/null > > to ensure the modules are loaded causes Linux to log errors. > > $ dmesg --level=err > [ 0.641747] [Firmware Bug]: TSC_DEADLINE disabled due to Errata; please update microcode to version: 0x3a (or later) > [ 40.196868] kvm: already loaded the other module > [ 40.219857] kvm: already loaded the other module > [ 55.501362] kvm [1177]: vcpu0, guest rIP: 0xffffffff96e5b644 disabled perfctr wrmsr: 0xc2 data 0xffff > [ 56.397974] kvm [1418]: vcpu0, guest rIP: 0xffffffff81046158 disabled perfctr wrmsr: 0xc1 data 0xabcd > [1007981.827781] kvm: already loaded the other module > [1008000.394089] kvm: already loaded the other module > [1008030.706999] kvm: already loaded the other module > [1020396.054470] kvm: already loaded the other module > [1020405.614774] kvm: already loaded the other module > [1020410.140069] kvm: already loaded the other module > [1020704.049231] kvm: already loaded the other module > > As one of the two KVM modules is already loaded, KVM is functioning, and > their is no error condition. Therefore, demote the log message level to > informational. > Shouldn't this return ENODEV when loading one of these modules instead as there is no hardware that supports both VMX and SVM? Thanks, Maciej
On Wed, Aug 18, 2021, Maciej S. Szmigiero wrote: > On 18.08.2021 13:49, Paul Menzel wrote: > > In scripts, running > > > > modprobe kvm_amd 2>/dev/null > > modprobe kvm_intel 2>/dev/null > > > > to ensure the modules are loaded causes Linux to log errors. > > > > $ dmesg --level=err > > [ 0.641747] [Firmware Bug]: TSC_DEADLINE disabled due to Errata; please update microcode to version: 0x3a (or later) > > [ 40.196868] kvm: already loaded the other module > > [ 40.219857] kvm: already loaded the other module > > [ 55.501362] kvm [1177]: vcpu0, guest rIP: 0xffffffff96e5b644 disabled perfctr wrmsr: 0xc2 data 0xffff > > [ 56.397974] kvm [1418]: vcpu0, guest rIP: 0xffffffff81046158 disabled perfctr wrmsr: 0xc1 data 0xabcd > > [1007981.827781] kvm: already loaded the other module > > [1008000.394089] kvm: already loaded the other module > > [1008030.706999] kvm: already loaded the other module > > [1020396.054470] kvm: already loaded the other module > > [1020405.614774] kvm: already loaded the other module > > [1020410.140069] kvm: already loaded the other module > > [1020704.049231] kvm: already loaded the other module > > > > As one of the two KVM modules is already loaded, KVM is functioning, and > > their is no error condition. Therefore, demote the log message level to > > informational. Hrm, but there is an error condition. Userspace explicitly requested something and KVM couldn't satisfy the request. KVM is also going to complain at level=err one way or another, e.g. if a script probes kvm_amd before kvm_intel on an Intel CPU it's going to get "kvm: no hardware support", so this isn't truly fixing the problem. Is the issue perhaps that this particular message isn't ratelimited? It's also easy for the script to grep /proc/cpuinfo, so it's hard to feel too bad about the kludgy message, e.g. look for a specific vendor, 'vmx' or 'svm', etc... if [[ -z $kvm ]]; then grep vendor_id "/proc/cpuinfo" | grep -q AuthenticAMD if [[ $? -eq 0 ]]; then kvm=kvm_amd else kvm=kvm_intel fi fi > Shouldn't this return ENODEV when loading one of these modules instead > as there is no hardware that supports both VMX and SVM? Probably not, as KVM would effectively be speculating, e.g. someone could load an out-of-tree variant of kvm_{intel,amd}. Maybe instead of switching to ENODEV, reword the comment, make it ratelimited, and shove it down? That way the message and -EEXIST fires iff the vendor module actually has some chance of being loaded. From 3528e66bd5107d5ac4f6a6ae50503cf64446866a Mon Sep 17 00:00:00 2001 From: Sean Christopherson <seanjc@google.com> Date: Wed, 18 Aug 2021 15:17:43 -0700 Subject: [PATCH] KVM: x86: Tweak handling and message when vendor module is already loaded Reword KVM's error message if a vendor module is already loaded to state exactly that instead of assuming "the other" module is loaded, ratelimit said message to match the other errors, and move the check down below the basic functionality checks so that attempting to load an unsupported module provides the same result regardless of whether or not a supported vendor module is already loaded. Reported-by: Paul Menzel <pmenzel@molgen.mpg.de> Cc: Maciej S. Szmigiero <mail@maciej.szmigiero.name> Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/kvm/x86.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index fdc0c18339fb..15bd4bd3c81d 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -8357,12 +8357,6 @@ int kvm_arch_init(void *opaque) struct kvm_x86_init_ops *ops = opaque; int r; - if (kvm_x86_ops.hardware_enable) { - printk(KERN_ERR "kvm: already loaded the other module\n"); - r = -EEXIST; - goto out; - } - if (!ops->cpu_has_kvm_support()) { pr_err_ratelimited("kvm: no hardware support\n"); r = -EOPNOTSUPP; @@ -8374,6 +8368,12 @@ int kvm_arch_init(void *opaque) goto out; } + if (kvm_x86_ops.hardware_enable) { + pr_err_ratelimited("kvm: already loaded a vendor module\n"); + r = -EEXIST; + goto out; + } + /* * KVM explicitly assumes that the guest has an FPU and * FXSAVE/FXRSTOR. For example, the KVM_GET_FPU explicitly casts the -- 2.33.0.rc2.250.ged5fa647cd-goog
Dear Sean, Am 19.08.21 um 00:23 schrieb Sean Christopherson: > On Wed, Aug 18, 2021, Maciej S. Szmigiero wrote: >> On 18.08.2021 13:49, Paul Menzel wrote: >>> In scripts, running >>> >>> modprobe kvm_amd 2>/dev/null >>> modprobe kvm_intel 2>/dev/null >>> >>> to ensure the modules are loaded causes Linux to log errors. >>> >>> $ dmesg --level=err >>> [ 0.641747] [Firmware Bug]: TSC_DEADLINE disabled due to Errata; please update microcode to version: 0x3a (or later) >>> [ 40.196868] kvm: already loaded the other module >>> [ 40.219857] kvm: already loaded the other module >>> [ 55.501362] kvm [1177]: vcpu0, guest rIP: 0xffffffff96e5b644 disabled perfctr wrmsr: 0xc2 data 0xffff >>> [ 56.397974] kvm [1418]: vcpu0, guest rIP: 0xffffffff81046158 disabled perfctr wrmsr: 0xc1 data 0xabcd >>> [1007981.827781] kvm: already loaded the other module >>> [1008000.394089] kvm: already loaded the other module >>> [1008030.706999] kvm: already loaded the other module >>> [1020396.054470] kvm: already loaded the other module >>> [1020405.614774] kvm: already loaded the other module >>> [1020410.140069] kvm: already loaded the other module >>> [1020704.049231] kvm: already loaded the other module >>> >>> As one of the two KVM modules is already loaded, KVM is functioning, and >>> their is no error condition. Therefore, demote the log message level to >>> informational. > > Hrm, but there is an error condition. Userspace explicitly requested something > and KVM couldn't satisfy the request. Yes, that’s the other perspective. ;-) I’d argue, as the Intel/AMD module can’t work on AMD/Intel, the load failure is expected and error. But as “error condition” is not well defined: $ dmesg -h […] Supported log levels (priorities): emerg - system is unusable alert - action must be taken immediately crit - critical conditions err - error conditions warn - warning conditions notice - normal but significant condition info - informational debug - debug-level messages > KVM is also going to complain at level=err one way or another, e.g. if a script > probes kvm_amd before kvm_intel on an Intel CPU it's going to get "kvm: no hardware > support", so this isn't truly fixing the problem. In my case, modprobe already errors out in that case, which is fine for me. $ lsmod | grep kvm kvm_intel 249856 0 kvm 851968 1 kvm_intel irqbypass 16384 1 kvm $ sudo modprobe -r kvm_intel $ sudo modprobe kvm_amd modprobe: ERROR: could not insert 'kvm_amd': Operation not supported $ dmesg | tail -2 [212685.034278] has_svm: not amd or hygon [212685.037998] kvm: no hardware support > Is the issue perhaps that this particular message isn't ratelimited? It would help my use case, as I am not interested in the error, and would be another solution than just changing the log levle. But for your viewpoint “Userspace explicitly requested something and KVM couldn't satisfy the request”, the user wouldn’t see the immediate error at the end of the output of `dmesg`. > It's also easy for the script to grep /proc/cpuinfo, so it's hard to feel too > bad about the kludgy message, e.g. look for a specific vendor, 'vmx' or 'svm', etc... > > if [[ -z $kvm ]]; then > grep vendor_id "/proc/cpuinfo" | grep -q AuthenticAMD > if [[ $? -eq 0 ]]; then > kvm=kvm_amd > else > kvm=kvm_intel > fi > fi Yes, it could be worked around. >> Shouldn't this return ENODEV when loading one of these modules instead >> as there is no hardware that supports both VMX and SVM? > > Probably not, as KVM would effectively be speculating, e.g. someone could load an > out-of-tree variant of kvm_{intel,amd}. Maybe instead of switching to ENODEV, > reword the comment, make it ratelimited, and shove it down? That way the message > and -EEXIST fires iff the vendor module actually has some chance of being loaded. > > From 3528e66bd5107d5ac4f6a6ae50503cf64446866a Mon Sep 17 00:00:00 2001 > From: Sean Christopherson <seanjc@google.com> > Date: Wed, 18 Aug 2021 15:17:43 -0700 > Subject: [PATCH] KVM: x86: Tweak handling and message when vendor module is > already loaded > > Reword KVM's error message if a vendor module is already loaded to state > exactly that instead of assuming "the other" module is loaded, The rewording is definitely an improvement. > ratelimit > said message to match the other errors, and move the check down below the > basic functionality checks so that attempting to load an unsupported > module provides the same result regardless of whether or not a supported > vendor module is already loaded. Maybe add an example, how it would log the error before, and how it’s done now. > Reported-by: Paul Menzel <pmenzel@molgen.mpg.de> > Cc: Maciej S. Szmigiero <mail@maciej.szmigiero.name> > Signed-off-by: Sean Christopherson <seanjc@google.com> > --- > arch/x86/kvm/x86.c | 12 ++++++------ > 1 file changed, 6 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index fdc0c18339fb..15bd4bd3c81d 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -8357,12 +8357,6 @@ int kvm_arch_init(void *opaque) > struct kvm_x86_init_ops *ops = opaque; > int r; > > - if (kvm_x86_ops.hardware_enable) { > - printk(KERN_ERR "kvm: already loaded the other module\n"); > - r = -EEXIST; > - goto out; > - } > - > if (!ops->cpu_has_kvm_support()) { > pr_err_ratelimited("kvm: no hardware support\n"); > r = -EOPNOTSUPP; > @@ -8374,6 +8368,12 @@ int kvm_arch_init(void *opaque) > goto out; > } > > + if (kvm_x86_ops.hardware_enable) { > + pr_err_ratelimited("kvm: already loaded a vendor module\n"); > + r = -EEXIST; > + goto out; > + } > + > /* > * KVM explicitly assumes that the guest has an FPU and > * FXSAVE/FXRSTOR. For example, the KVM_GET_FPU explicitly casts the > -- > 2.33.0.rc2.250.ged5fa647cd-goog Sounds also good at first sight. No idea, if monitoring scripts in userspace would get confused now. Kind regards, Paul
On 19.08.2021 08:39, Paul Menzel wrote: > Am 19.08.21 um 00:23 schrieb Sean Christopherson: >> On Wed, Aug 18, 2021, Maciej S. Szmigiero wrote: >>> On 18.08.2021 13:49, Paul Menzel wrote: >>>> In scripts, running >>>> >>>> modprobe kvm_amd 2>/dev/null >>>> modprobe kvm_intel 2>/dev/null >>>> >>>> to ensure the modules are loaded causes Linux to log errors. >>>> >>>> $ dmesg --level=err >>>> [ 0.641747] [Firmware Bug]: TSC_DEADLINE disabled due to Errata; please update microcode to version: 0x3a (or later) >>>> [ 40.196868] kvm: already loaded the other module >>>> [ 40.219857] kvm: already loaded the other module >>>> [ 55.501362] kvm [1177]: vcpu0, guest rIP: 0xffffffff96e5b644 disabled perfctr wrmsr: 0xc2 data 0xffff >>>> [ 56.397974] kvm [1418]: vcpu0, guest rIP: 0xffffffff81046158 disabled perfctr wrmsr: 0xc1 data 0xabcd >>>> [1007981.827781] kvm: already loaded the other module >>>> [1008000.394089] kvm: already loaded the other module >>>> [1008030.706999] kvm: already loaded the other module >>>> [1020396.054470] kvm: already loaded the other module >>>> [1020405.614774] kvm: already loaded the other module >>>> [1020410.140069] kvm: already loaded the other module >>>> [1020704.049231] kvm: already loaded the other module >>>> >>>> As one of the two KVM modules is already loaded, KVM is functioning, and >>>> their is no error condition. Therefore, demote the log message level to >>>> informational. >> >> Hrm, but there is an error condition. Userspace explicitly requested something >> and KVM couldn't satisfy the request. > > Yes, that’s the other perspective. ;-) I’d argue, as the Intel/AMD module can’t work on AMD/Intel, the load failure is expected and error. But as “error condition” is not well defined: > > $ dmesg -h > […] > Supported log levels (priorities): > emerg - system is unusable > alert - action must be taken immediately > crit - critical conditions > err - error conditions > warn - warning conditions > notice - normal but significant condition > info - informational > debug - debug-level messages > Why is that script repeatably trying to load kvm_amd and kvm_intel modules? I would assume these would be loaded once at system boot time (either manually or based on their modalias). If your script absolutely has to load them manually, it could check first whether /dev/kvm already exists. >>> Shouldn't this return ENODEV when loading one of these modules instead >>> as there is no hardware that supports both VMX and SVM? >> >> Probably not, as KVM would effectively be speculating, e.g. someone could load an >> out-of-tree variant of kvm_{intel,amd}. Maybe instead of switching to ENODEV, >> reword the comment, make it ratelimited, and shove it down? That way the message >> and -EEXIST fires iff the vendor module actually has some chance of being loaded. >> >> From 3528e66bd5107d5ac4f6a6ae50503cf64446866a Mon Sep 17 00:00:00 2001 >> From: Sean Christopherson <seanjc@google.com> >> Date: Wed, 18 Aug 2021 15:17:43 -0700 >> Subject: [PATCH] KVM: x86: Tweak handling and message when vendor module is >> already loaded >> >> Reword KVM's error message if a vendor module is already loaded to state >> exactly that instead of assuming "the other" module is loaded, > > The rewording is definitely an improvement. > >> ratelimit >> said message to match the other errors, and move the check down below the >> basic functionality checks so that attempting to load an unsupported >> module provides the same result regardless of whether or not a supported >> vendor module is already loaded. > > Maybe add an example, how it would log the error before, and how it’s done now. > >> Reported-by: Paul Menzel <pmenzel@molgen.mpg.de> >> Cc: Maciej S. Szmigiero <mail@maciej.szmigiero.name> >> Signed-off-by: Sean Christopherson <seanjc@google.com> >> --- >> arch/x86/kvm/x86.c | 12 ++++++------ >> 1 file changed, 6 insertions(+), 6 deletions(-) >> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >> index fdc0c18339fb..15bd4bd3c81d 100644 >> --- a/arch/x86/kvm/x86.c >> +++ b/arch/x86/kvm/x86.c >> @@ -8357,12 +8357,6 @@ int kvm_arch_init(void *opaque) >> struct kvm_x86_init_ops *ops = opaque; >> int r; >> >> - if (kvm_x86_ops.hardware_enable) { >> - printk(KERN_ERR "kvm: already loaded the other module\n"); >> - r = -EEXIST; >> - goto out; >> - } >> - >> if (!ops->cpu_has_kvm_support()) { >> pr_err_ratelimited("kvm: no hardware support\n"); >> r = -EOPNOTSUPP; >> @@ -8374,6 +8368,12 @@ int kvm_arch_init(void *opaque) >> goto out; >> } >> >> + if (kvm_x86_ops.hardware_enable) { >> + pr_err_ratelimited("kvm: already loaded a vendor module\n"); >> + r = -EEXIST; >> + goto out; >> + } >> + >> /* >> * KVM explicitly assumes that the guest has an FPU and >> * FXSAVE/FXRSTOR. For example, the KVM_GET_FPU explicitly casts the >> -- >> 2.33.0.rc2.250.ged5fa647cd-goog > > Sounds also good at first sight. No idea, if monitoring scripts in userspace would get confused now. This definitely looks more informative than the existing message. It would be even better if it wasn't "kvm: no hardware support" (as this message is technically incorrect), but something like "kvm: no VMX hardware support" or "kvm: no SVM hardware support". > Kind regards, > > Paul Thanks, Maciej
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index e5d5c5ed7dd4..411c58ae0c97 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -8372,7 +8372,7 @@ int kvm_arch_init(void *opaque) int r; if (kvm_x86_ops.hardware_enable) { - printk(KERN_ERR "kvm: already loaded the other module\n"); + printk(KERN_INFO "kvm: already loaded the other module\n"); r = -EEXIST; goto out; }
In scripts, running modprobe kvm_amd 2>/dev/null modprobe kvm_intel 2>/dev/null to ensure the modules are loaded causes Linux to log errors. $ dmesg --level=err [ 0.641747] [Firmware Bug]: TSC_DEADLINE disabled due to Errata; please update microcode to version: 0x3a (or later) [ 40.196868] kvm: already loaded the other module [ 40.219857] kvm: already loaded the other module [ 55.501362] kvm [1177]: vcpu0, guest rIP: 0xffffffff96e5b644 disabled perfctr wrmsr: 0xc2 data 0xffff [ 56.397974] kvm [1418]: vcpu0, guest rIP: 0xffffffff81046158 disabled perfctr wrmsr: 0xc1 data 0xabcd [1007981.827781] kvm: already loaded the other module [1008000.394089] kvm: already loaded the other module [1008030.706999] kvm: already loaded the other module [1020396.054470] kvm: already loaded the other module [1020405.614774] kvm: already loaded the other module [1020410.140069] kvm: already loaded the other module [1020704.049231] kvm: already loaded the other module As one of the two KVM modules is already loaded, KVM is functioning, and their is no error condition. Therefore, demote the log message level to informational. Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de> --- arch/x86/kvm/x86.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)