[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH] x86/vm_event: transfer nested p2m base info
On Mon, Jan 4, 2021 at 6:57 AM Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote: > > On 03/01/2021 18:41, Tamas K Lengyel wrote: > > Required to introspect events originating from nested VMs. > > > > Signed-off-by: Tamas K Lengyel <tamas@xxxxxxxxxxxxx> > > --- > > xen/arch/x86/hvm/monitor.c | 32 ++++++++++++++++++++++++++++++-- > > xen/include/public/vm_event.h | 7 ++++++- > > 2 files changed, 36 insertions(+), 3 deletions(-) > > > > diff --git a/xen/arch/x86/hvm/monitor.c b/xen/arch/x86/hvm/monitor.c > > index e4a09964a0..eb4afe81b3 100644 > > --- a/xen/arch/x86/hvm/monitor.c > > +++ b/xen/arch/x86/hvm/monitor.c > > @@ -26,6 +26,7 @@ > > #include <xen/mem_access.h> > > #include <xen/monitor.h> > > #include <asm/hvm/monitor.h> > > +#include <asm/hvm/nestedhvm.h> > > #include <asm/altp2m.h> > > #include <asm/monitor.h> > > #include <asm/p2m.h> > > @@ -33,6 +34,15 @@ > > #include <asm/vm_event.h> > > #include <public/vm_event.h> > > > > +static inline void set_npt_base(struct vcpu *curr, vm_event_request_t *req) > > No need for inline here. Can fix on commit. > > > diff --git a/xen/include/public/vm_event.h b/xen/include/public/vm_event.h > > index fdd3ad8a30..8415bc7618 100644 > > --- a/xen/include/public/vm_event.h > > +++ b/xen/include/public/vm_event.h > > @@ -208,6 +212,7 @@ struct vm_event_regs_x86 { > > uint64_t msr_star; > > uint64_t msr_lstar; > > uint64_t gdtr_base; > > + uint64_t npt_base; > > This needs enough description to actually use it correctly. > > /* Guest physical address. On Intel hardware, this is the EPT_POINTER > field from the L1 hypervisors VMCS, including all architecturally > defined metadata. */ > > Except, its not. nvmx_vcpu_eptp_base() masks out the lower metadata, so > the walk length is missing, and the introspection agent can't > distinguish between 4 and 5 level EPT. Same on the AMD side (except it > could be any paging mode, including 2 and 3 level). AMD is AFAIK not supported for vm_events. Also, only 4L EPT is available at this time, so that information is irrelevant anyway. > > Furthermore, (and more in reference to your pagewalk patch), it might be > necessary to know whether EPT A/D is enabled for the agent to do the > correct thing when getting a gla-not-valid fault. Not for a translation. For use-cases where they need to know whether the page got modified (and want to use A/D for that instead of tracking such modifications with mem_access), sure, but I'm not aware of such a use-case. So I would leave that up as a TODO for the time when it's actually needed. Tamas
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