[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH RFC V2 6/6] xen: Handle resumed instruction based on previous mem_event reply
On 11/07/14 19:41, Razvan Cojocaru wrote: > On 07/11/2014 09:36 PM, Andrew Cooper wrote: >> On 11/07/14 16:43, Razvan Cojocaru wrote: >>> In a scenario where a page fault that triggered a mem_event occured, >>> p2m_mem_access_check() will now be able to either 1) emulate the >>> current instruction, or 2) emulate it, but don't allow it to perform >>> any writes. >>> >>> Changes since V1: >>> - Removed the 'skip' code which required computing the current >>> instruction length. >>> - Removed the set_ad_bits() code that attempted to modify the >>> 'accessed' and 'dirty' bits for instructions that the emulator >>> can't handle at the moment. >>> >>> Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx> >>> --- >>> xen/arch/x86/domain.c | 5 +++ >>> xen/arch/x86/mm/p2m.c | 90 >>> ++++++++++++++++++++++++++++++++++++++++ >>> xen/include/asm-x86/domain.h | 9 ++++ >>> xen/include/public/mem_event.h | 12 +++--- >>> 4 files changed, 111 insertions(+), 5 deletions(-) >>> >>> diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c >>> index e896210..5cd283b 100644 >>> --- a/xen/arch/x86/domain.c >>> +++ b/xen/arch/x86/domain.c >>> @@ -407,6 +407,11 @@ int vcpu_initialise(struct vcpu *v) >>> >>> v->arch.flags = TF_kernel_mode; >>> >>> + /* By default, do not emulate */ >>> + v->arch.mem_event.emulate_flags = 0; >>> + v->arch.mem_event.gpa = 0; >>> + v->arch.mem_event.eip = 0; >>> + >>> rc = mapcache_vcpu_init(v); >>> if ( rc ) >>> return rc; >>> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c >>> index 13fdf78..7aff480 100644 >>> --- a/xen/arch/x86/mm/p2m.c >>> +++ b/xen/arch/x86/mm/p2m.c >>> @@ -1377,6 +1377,7 @@ bool_t p2m_mem_access_check(paddr_t gpa, bool_t >>> gla_valid, unsigned long gla, >>> { >>> struct vcpu *v = current; >>> unsigned long gfn = gpa >> PAGE_SHIFT; >>> + unsigned long exit_qualification; >>> struct domain *d = v->domain; >>> struct p2m_domain* p2m = p2m_get_hostp2m(d); >>> mfn_t mfn; >>> @@ -1384,6 +1385,9 @@ bool_t p2m_mem_access_check(paddr_t gpa, bool_t >>> gla_valid, unsigned long gla, >>> p2m_access_t p2ma; >>> mem_event_request_t *req; >>> int rc; >>> + unsigned long eip = guest_cpu_user_regs()->eip; >>> + >>> + __vmread(EXIT_QUALIFICATION, &exit_qualification); >> This absolutely can't be put into common code. I presume you haven't >> attempted to run a Xen patched with this on an AMD cpu ? > Indeed, we have not. I think that for a while there wasn't even support > for mem_even when compiling for AMD, so there wasn't really even a choice. > > What would be the best way to get that value in a cross-CPU manner? > > > Thanks, > Razvan Cojocaru The problem is that it will die with a fatal invalid opcode exception, as AMD cpus won't know execute the vmread instruction. Code using __vmread() must live in arch/x86/hvm/vmx/* and have some generic hvm way of accessing the required information. Also bear in mind that the exit qualification is also architecture specific, so you will need a more general way of representing "the guest exited because of a pagefault". ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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