[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] Limit MCG Cap
Hi Keir -Your suggestion to report 0 for reads of MSR_IA32_MCG_CAP seems to be working well on a wide variety of HVM guests (Windows & Linux, 32 & 64bit). I've attached a new patch. Thanks, DaveThis patch implements a suggestion of Keir's (in response to a patch of mine): Intercept guest reads of MSR_IA32_MCG_CAP and report 0, indicating no machine check "units", which agrees more closely with Xen's super-minimal machine check architecture (just enough to allow Windows to run). This fixes a bug that occurs when migrating a RHEL4-64bit guest to a host with fewer machine check units than the original host. These host physical details shouldn't be leaking through to guests. Signed-off-by: David Lively <dlively@xxxxxxxxxxxxxxx> Keir Fraser wrote: Given that we don't properly virtualise/emulate machine check (we only set the feature bit because some versions of Windows demand it) can we get away with returning zero for reads of MCG_CAP? -- Keir On 27/8/07 20:11, "Ben Guthro" <bguthro@xxxxxxxxxxxxxxx> wrote:Intercept guest reads of MSR_IA32_MCG_CAP and limit the number of memory banks reported to one. This prevents us from trying to read status of non-existent banks when migrated to a machine with fewer banks. diff -r 9f111c7d648f xen/arch/x86/hvm/svm/svm.c --- a/xen/arch/x86/hvm/svm/svm.c Tue Aug 28 22:40:01 2007 -0400 +++ b/xen/arch/x86/hvm/svm/svm.c Tue Aug 28 22:40:01 2007 -0400 @@ -2058,6 +2058,9 @@ static inline void svm_do_msr_access( */ msr_content = 0; break; + case MSR_IA32_MCG_CAP: + msr_content = 0; + break; default: if ( rdmsr_hypervisor_regs(ecx, &eax, &edx) || rdmsr_safe(ecx, eax, edx) == 0 ) diff -r 9f111c7d648f xen/arch/x86/hvm/vmx/vmx.c --- a/xen/arch/x86/hvm/vmx/vmx.c Tue Aug 28 22:40:01 2007 -0400 +++ b/xen/arch/x86/hvm/vmx/vmx.c Tue Aug 28 22:40:01 2007 -0400 @@ -2554,6 +2554,9 @@ static inline int vmx_do_msr_read(struct case MSR_IA32_APICBASE: msr_content = vcpu_vlapic(v)->hw.apic_base_msr; break; + case MSR_IA32_MCG_CAP: + msr_content = 0; + break; default: if ( long_mode_do_msr_read(regs) ) goto done; _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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