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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] vMCE vs migration
On Mon, 2012-01-30 at 13:47 +0000, Jan Beulich wrote:
> >>> On 26.01.12 at 17:54, George Dunlap <george.dunlap@xxxxxxxxxx> wrote:
> > On Tue, 2012-01-24 at 11:08 +0000, Jan Beulich wrote:
> >> >>> On 24.01.12 at 11:29, George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
> >> >>> wrote:
> >> > On Mon, Jan 23, 2012 at 11:08 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
> >> >> x86's vMCE implementation lets a guest know of as many MCE reporting
> >> >> banks as there are in the host. While a PV guest could be expected to
> >> >> deal with this number changing (particularly decreasing) during
> >> >> migration
> >> >> (not currently handled anywhere afaict), for HVM guests this is
> >> >> certainly
> >> >> wrong.
> >> >>
> >> >> At least to me it isn't, however, clear how to properly handle this. The
> >> >> easiest would appear to be to save and restore the number of banks
> >> >> the guest was made believe it can access, making vmce_{rd,wr}msr()
> >> >> silently tolerate accesses between the host and guest values.
> >> >
> >> > We ran into this in the XS 6.0 release as well. I think that the
> >> > ideal thing to do would be to have a parameter that can be set at
> >> > boot, to say how many vMCE banks a guest has, defaulting to the number
> >> > of MCE banks on the host. This parameter would be preserved across
> >> > migration. Ideally, a pool-aware toolstack like xapi would then set
> >> > this value to be the value of the host in the pool with the largest
> >> > number of banks, allowing a guest to access all the banks on any host
> >> > to which it migrates.
> >> >
> >> > What do you think?
> >>
> >> That sounds like the way to go.
> >
> > So should we put this on IanC's to-do-be-done list? Are you going to
> > put it on your to-do list? :-)
>
> Below/attached a draft patch (compile tested only), handling save/
> restore of the bank count, but not allowing for a config setting to
> specify its initial value (yet).
Looks pretty good for a first blush. Just one question: Why is the vmce
count made on a per-vcpu basis, rather than on a per-domain basis, like
the actual banks are? Is the host MCE stuff per-vcpu?
-George
> +static int bank_mce_rdmsr(const struct vcpu *v, uint32_t msr, uint64_t *val)
> +{
> + int ret = 1;
> + unsigned int bank = (msr - MSR_IA32_MC0_CTL) / 4;
> + struct domain_mca_msrs *vmce = dom_vmce(v->domain);
> struct bank_entry *entry;
>
> - bank = (msr - MSR_IA32_MC0_CTL) / 4;
> - if ( bank >= nr_mce_banks )
> - return -1;
> + *val = 0;
>
> switch ( msr & (MSR_IA32_MC0_CTL | 3) )
> {
> case MSR_IA32_MC0_CTL:
> - *val = vmce->mci_ctl[bank] &
> - (h_mci_ctrl ? h_mci_ctrl[bank] : ~0UL);
> + if ( bank < nr_mce_banks )
> + *val = vmce->mci_ctl[bank] &
> + (h_mci_ctrl ? h_mci_ctrl[bank] : ~0UL);
> mce_printk(MCE_VERBOSE, "MCE: rdmsr MC%u_CTL 0x%"PRIx64"\n",
> bank, *val);
> break;
> @@ -126,7 +132,7 @@ static int bank_mce_rdmsr(struct domain
> switch ( boot_cpu_data.x86_vendor )
> {
> case X86_VENDOR_INTEL:
> - ret = intel_mce_rdmsr(msr, val);
> + ret = intel_mce_rdmsr(v, msr, val);
> break;
> default:
> ret = 0;
> @@ -145,13 +151,13 @@ static int bank_mce_rdmsr(struct domain
> */
> int vmce_rdmsr(uint32_t msr, uint64_t *val)
> {
> - struct domain *d = current->domain;
> - struct domain_mca_msrs *vmce = dom_vmce(d);
> + const struct vcpu *cur = current;
> + struct domain_mca_msrs *vmce = dom_vmce(cur->domain);
> int ret = 1;
>
> *val = 0;
>
> - spin_lock(&dom_vmce(d)->lock);
> + spin_lock(&vmce->lock);
>
> switch ( msr )
> {
> @@ -173,28 +179,26 @@ int vmce_rdmsr(uint32_t msr, uint64_t *v
> *val);
> break;
> default:
> - ret = mce_bank_msr(msr) ? bank_mce_rdmsr(d, msr, val) : 0;
> + ret = mce_bank_msr(cur, msr) ? bank_mce_rdmsr(cur, msr, val) : 0;
> break;
> }
>
> - spin_unlock(&dom_vmce(d)->lock);
> + spin_unlock(&vmce->lock);
> return ret;
> }
>
> -static int bank_mce_wrmsr(struct domain *d, u32 msr, u64 val)
> +static int bank_mce_wrmsr(struct vcpu *v, u32 msr, u64 val)
> {
> - int bank, ret = 1;
> - struct domain_mca_msrs *vmce = dom_vmce(d);
> + int ret = 1;
> + unsigned int bank = (msr - MSR_IA32_MC0_CTL) / 4;
> + struct domain_mca_msrs *vmce = dom_vmce(v->domain);
> struct bank_entry *entry = NULL;
>
> - bank = (msr - MSR_IA32_MC0_CTL) / 4;
> - if ( bank >= nr_mce_banks )
> - return -EINVAL;
> -
> switch ( msr & (MSR_IA32_MC0_CTL | 3) )
> {
> case MSR_IA32_MC0_CTL:
> - vmce->mci_ctl[bank] = val;
> + if ( bank < nr_mce_banks )
> + vmce->mci_ctl[bank] = val;
> break;
> case MSR_IA32_MC0_STATUS:
> /* Give the first entry of the list, it corresponds to current
> @@ -202,9 +206,9 @@ static int bank_mce_wrmsr(struct domain
> * the guest, this node will be deleted.
> * Only error bank is written. Non-error banks simply return.
> */
> - if ( !list_empty(&dom_vmce(d)->impact_header) )
> + if ( !list_empty(&vmce->impact_header) )
> {
> - entry = list_entry(dom_vmce(d)->impact_header.next,
> + entry = list_entry(vmce->impact_header.next,
> struct bank_entry, list);
> if ( entry->bank == bank )
> entry->mci_status = val;
> @@ -228,7 +232,7 @@ static int bank_mce_wrmsr(struct domain
> switch ( boot_cpu_data.x86_vendor )
> {
> case X86_VENDOR_INTEL:
> - ret = intel_mce_wrmsr(msr, val);
> + ret = intel_mce_wrmsr(v, msr, val);
> break;
> default:
> ret = 0;
> @@ -247,9 +251,9 @@ static int bank_mce_wrmsr(struct domain
> */
> int vmce_wrmsr(u32 msr, u64 val)
> {
> - struct domain *d = current->domain;
> + struct vcpu *cur = current;
> struct bank_entry *entry = NULL;
> - struct domain_mca_msrs *vmce = dom_vmce(d);
> + struct domain_mca_msrs *vmce = dom_vmce(cur->domain);
> int ret = 1;
>
> if ( !g_mcg_cap )
> @@ -266,7 +270,7 @@ int vmce_wrmsr(u32 msr, u64 val)
> vmce->mcg_status = val;
> mce_printk(MCE_VERBOSE, "MCE: wrmsr MCG_STATUS %"PRIx64"\n", val);
> /* For HVM guest, this is the point for deleting vMCE injection node
> */
> - if ( d->is_hvm && (vmce->nr_injection > 0) )
> + if ( is_hvm_vcpu(cur) && (vmce->nr_injection > 0) )
> {
> vmce->nr_injection--; /* Should be 0 */
> if ( !list_empty(&vmce->impact_header) )
> @@ -293,7 +297,7 @@ int vmce_wrmsr(u32 msr, u64 val)
> ret = -1;
> break;
> default:
> - ret = mce_bank_msr(msr) ? bank_mce_wrmsr(d, msr, val) : 0;
> + ret = mce_bank_msr(cur, msr) ? bank_mce_wrmsr(cur, msr, val) : 0;
> break;
> }
>
> @@ -301,6 +305,47 @@ int vmce_wrmsr(u32 msr, u64 val)
> return ret;
> }
>
> +static int vmce_save_vcpu_ctxt(struct domain *d, hvm_domain_context_t *h)
> +{
> + struct vcpu *v;
> + int err = 0;
> +
> + for_each_vcpu( d, v ) {
> + struct hvm_vmce_vcpu ctxt = {
> + .nr_banks = v->arch.nr_vmce_banks
> + };
> +
> + err = hvm_save_entry(VMCE_VCPU, v->vcpu_id, h, &ctxt);
> + if ( err )
> + break;
> + }
> +
> + return err;
> +}
> +
> +static int vmce_load_vcpu_ctxt(struct domain *d, hvm_domain_context_t *h)
> +{
> + unsigned int vcpuid = hvm_load_instance(h);
> + struct vcpu *v;
> + struct hvm_vmce_vcpu ctxt;
> + int err;
> +
> + if ( vcpuid >= d->max_vcpus || (v = d->vcpu[vcpuid]) == NULL )
> + {
> + gdprintk(XENLOG_ERR, "HVM restore: domain has no vcpu %u\n", vcpuid);
> + return -EINVAL;
> + }
> +
> + err = hvm_load_entry(VMCE_VCPU, h, &ctxt);
> + if ( !err )
> + v->arch.nr_vmce_banks = ctxt.nr_banks;
> +
> + return err;
> +}
> +
> +HVM_REGISTER_SAVE_RESTORE(VMCE_VCPU, vmce_save_vcpu_ctxt,
> + vmce_load_vcpu_ctxt, 1, HVMSR_PER_VCPU);
> +
> int inject_vmce(struct domain *d)
> {
> int cpu = smp_processor_id();
> --- a/xen/arch/x86/domain.c
> +++ b/xen/arch/x86/domain.c
> @@ -468,6 +468,8 @@ int vcpu_initialise(struct vcpu *v)
>
> v->arch.pv_vcpu.ctrlreg[4] = real_cr4_to_pv_guest_cr4(mmu_cr4_features);
>
> + vmce_init_vcpu(v);
> +
> rc = is_pv_32on64_vcpu(v) ? setup_compat_l4(v) : 0;
> done:
> if ( rc )
> --- a/xen/arch/x86/domctl.c
> +++ b/xen/arch/x86/domctl.c
> @@ -1027,11 +1027,12 @@ long arch_do_domctl(
> evc->syscall32_callback_eip = 0;
> evc->syscall32_disables_events = 0;
> }
> + evc->nr_mce_banks = v->arch.nr_vmce_banks;
> }
> else
> {
> ret = -EINVAL;
> - if ( evc->size != sizeof(*evc) )
> + if ( evc->size < offsetof(typeof(*evc), nr_mce_banks) )
> goto ext_vcpucontext_out;
> #ifdef __x86_64__
> if ( !is_hvm_domain(d) )
> @@ -1059,6 +1060,16 @@ long arch_do_domctl(
> (evc->syscall32_callback_cs & ~3) ||
> evc->syscall32_callback_eip )
> goto ext_vcpucontext_out;
> +
> + if ( evc->size >= offsetof(typeof(*evc),
> mbz[ARRAY_SIZE(evc->mbz)]) )
> + {
> + unsigned int i;
> +
> + for ( i = 0; i < ARRAY_SIZE(evc->mbz); ++i )
> + if ( evc->mbz[i] )
> + goto ext_vcpucontext_out;
> + v->arch.nr_vmce_banks = evc->nr_mce_banks;
> + }
> }
>
> ret = 0;
> --- a/xen/include/asm-x86/domain.h
> +++ b/xen/include/asm-x86/domain.h
> @@ -488,6 +488,8 @@ struct arch_vcpu
> /* This variable determines whether nonlazy extended state has been used,
> * and thus should be saved/restored. */
> bool_t nonlazy_xstate_used;
> +
> + uint8_t nr_vmce_banks;
>
> struct paging_vcpu paging;
>
> --- a/xen/include/asm-x86/mce.h
> +++ b/xen/include/asm-x86/mce.h
> @@ -28,6 +28,7 @@ struct domain_mca_msrs
> /* Guest vMCE MSRs virtualization */
> extern int vmce_init_msr(struct domain *d);
> extern void vmce_destroy_msr(struct domain *d);
> +extern void vmce_init_vcpu(struct vcpu *);
> extern int vmce_wrmsr(uint32_t msr, uint64_t val);
> extern int vmce_rdmsr(uint32_t msr, uint64_t *val);
>
> --- a/xen/include/public/arch-x86/hvm/save.h
> +++ b/xen/include/public/arch-x86/hvm/save.h
> @@ -585,9 +585,15 @@ struct hvm_viridian_vcpu_context {
>
> DECLARE_HVM_SAVE_TYPE(VIRIDIAN_VCPU, 17, struct hvm_viridian_vcpu_context);
>
> +struct hvm_vmce_vcpu {
> + uint8_t nr_banks;
> +};
> +
> +DECLARE_HVM_SAVE_TYPE(VMCE_VCPU, 18, struct hvm_vmce_vcpu);
> +
> /*
> * Largest type-code in use
> */
> -#define HVM_SAVE_CODE_MAX 17
> +#define HVM_SAVE_CODE_MAX 18
>
> #endif /* __XEN_PUBLIC_HVM_SAVE_X86_H__ */
> --- a/xen/include/public/domctl.h
> +++ b/xen/include/public/domctl.h
> @@ -559,7 +559,7 @@ struct xen_domctl_ext_vcpucontext {
> uint32_t vcpu;
> /*
> * SET: Size of struct (IN)
> - * GET: Size of struct (OUT)
> + * GET: Size of struct (OUT, up to 128 bytes)
> */
> uint32_t size;
> #if defined(__i386__) || defined(__x86_64__)
> @@ -571,6 +571,10 @@ struct xen_domctl_ext_vcpucontext {
> uint16_t sysenter_callback_cs;
> uint8_t syscall32_disables_events;
> uint8_t sysenter_disables_events;
> + uint8_t nr_mce_banks;
> + /* This array can be split and used for future extension. */
> + /* It is there just to grow the structure beyond 4.1's size. */
> + uint8_t mbz[9];
> #endif
> };
> typedef struct xen_domctl_ext_vcpucontext xen_domctl_ext_vcpucontext_t;
>
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