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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] Re: [PATCH 13/13] Nested Virtualiztion: hap-on-hap
On Wednesday 08 September 2010 16:04:51 Tim Deegan wrote:
> Hi,
>
> This is looking better - I think the TLB flushing is almost right.
> A few more detailed comments below.
>
> Content-Description: xen_nh13_haphap.diff
>
> > # HG changeset patch
> > # User cegger
> > # Date 1283345895 -7200
> > Implement Nested-on-Nested.
> > This allows the guest to run nested guest with hap enabled.
> >
> > diff -r 50b3e6c73d7c -r 24daea64bdff xen/arch/x86/hvm/hvm.c
> > --- a/xen/arch/x86/hvm/hvm.c
> > +++ b/xen/arch/x86/hvm/hvm.c
> > @@ -1042,12 +1042,56 @@ void hvm_inject_exception(unsigned int t
> > hvm_funcs.inject_exception(trapnr, errcode, cr2);
> > }
> >
> > -bool_t hvm_hap_nested_page_fault(unsigned long gfn)
> > +bool_t hvm_hap_nested_page_fault(paddr_t gpa, struct cpu_user_regs
> > *regs) {
> > p2m_type_t p2mt;
> > mfn_t mfn;
> > struct vcpu *v = current;
> > struct p2m_domain *p2m = p2m_get_hostp2m(v->domain);
> > + unsigned long gfn = gpa >> PAGE_SHIFT;
> > + int rv;
> > +
> > + /* On Nested Virtualization, walk the guest page table.
> > + * If this succeeds, all is fine.
> > + * If this fails, inject a nested page fault into the guest.
> > + */
> > + if ( nestedhvm_enabled(v->domain)
> > + && nestedhvm_vcpu_in_guestmode(v)
> > + && nestedhvm_paging_mode_hap(v) )
> > + {
> > + enum nestedhvm_vmexits nsret;
> > + struct nestedhvm *hvm = &vcpu_nestedhvm(v);
> > +
> > + /* nested guest gpa == guest gva */
>
> This comment is confusing to me. The nested guest gpa isn't a virtual
> address, and certainly not the same as an L1-guest VA. Can you reword
> it, maybe just to say what the call to nestedhvm_hap_nested_page_fault()
> is going to do?
New wording is:
/* The vcpu is in guest mdoe and the l1 guest
* uses hap. That means 'gpa' is in l2 guest
* physical adderss space.
* Fix the nested p2m or inject nested page fault
* into l1 guest if not fixable. The algorithm is
* the same as for shadow paging.
*/
Is this fine with you ?
>
> > + rv = nestedhvm_hap_nested_page_fault(v, gpa);
> > + switch (rv) {
> > + case NESTEDHVM_PAGEFAULT_DONE:
> > + return 1;
> > + case NESTEDHVM_PAGEFAULT_ERROR:
> > + return 0;
> > + case NESTEDHVM_PAGEFAULT_INJECT:
> > + break;
> > + }
> > +
> > + /* inject #VMEXIT(NPF) into guest. */
> > + hvm->nh_forcevmexit.exitcode = NESTEDHVM_INTERCEPT_NPF;
> > + hvm->nh_forcevmexit.exitinfo1 = regs->error_code;
> > + hvm->nh_forcevmexit.exitinfo2 = gpa;
> > + hvm->nh_hostflags.fields.forcevmexit = 1;
> > + nsret = nestedhvm_vcpu_vmexit(v, regs, NESTEDHVM_INTERCEPT_NPF);
> > + hvm->nh_hostflags.fields.forcevmexit = 0;
> > + switch (nsret) {
> > + case NESTEDHVM_VMEXIT_DONE:
> > + case NESTEDHVM_VMEXIT_ERROR: /* L1 guest will crash L2 guest */
> > + return 1;
> > + case NESTEDHVM_VMEXIT_HOST:
> > + case NESTEDHVM_VMEXIT_CONTINUE:
> > + case NESTEDHVM_VMEXIT_FATALERROR:
> > + default:
> > + gdprintk(XENLOG_ERR, "unexpected nestedhvm error %i\n",
> > nsret); + return 0;
> > + }
> > + }
> >
> > mfn = gfn_to_mfn_guest(p2m, gfn, &p2mt);
> >
> >
> > @@ -1843,7 +1908,7 @@ static enum hvm_copy_result __hvm_copy(
> >
> > if ( flags & HVMCOPY_virt )
> > {
> > - gfn = paging_gva_to_gfn(curr, addr, &pfec);
> > + gfn = paging_p2m_ga_to_gfn(curr, p2m, mode, cr3, addr,
> > &pfec);
>
> Do other callers of paging_gva_to_gfn need to handle nested-npt mode as
> well?
If the other callers can be reached when the vcpu is in guest mode, then yes.
> If so, would it be better to update paging_gva_to_gfn() itself?
This is definitely easier but the call to p2m_get_p2m() might become be very
expensive and should be cached by passing through per function argument.
> > if ( gfn == INVALID_GFN )
> > {
> > if ( pfec == PFEC_page_paged )
> > diff -r 50b3e6c73d7c -r 24daea64bdff xen/arch/x86/hvm/nestedhvm.c
> > --- a/xen/arch/x86/hvm/nestedhvm.c
> > +++ b/xen/arch/x86/hvm/nestedhvm.c
> > @@ -20,6 +20,7 @@
> > #include <asm/msr.h>
> > #include <asm/hvm/support.h> /* for HVM_DELIVER_NO_ERROR_CODE */
> > #include <asm/hvm/hvm.h>
> > +#include <asm/p2m.h> /* for struct p2m_domain */
> > #include <asm/hvm/nestedhvm.h>
> > #include <asm/event.h> /* for local_event_delivery_(en|dis)able */
> > #include <asm/paging.h> /* for paging_mode_hap() */
> > @@ -477,6 +478,7 @@ nestedhvm_vcpu_vmexit(struct vcpu *v, st
> > enum hvm_copy_result hvm_rc;
> >
> > hvm->nh_hostflags.fields.vmentry = 1;
> > + paging_update_nestedmode(v);
> > if (nestedhvm_vcpu_in_guestmode(v)) {
> > ret = nestedhvm_vmexit(v, regs, exitcode);
> > switch (ret) {
> > @@ -529,14 +531,30 @@ nestedhvm_vcpu_vmexit(struct vcpu *v, st
> > void
> > nestedhvm_vcpu_enter_guestmode(struct vcpu *v)
> > {
> > + struct p2m_domain *p2m;
> > vcpu_nestedhvm(v).nh_guestmode = 1;
> > +
> > + p2m = vcpu_nestedhvm(v).nh_p2m;
> > + if (p2m == NULL)
> > + /* p2m has either been invalidated or not yet assigned. */
> > + return;
> > +
> > + cpu_set(v->processor, p2m->p2m_dirty_cpumask);
>
> Is this arch-specific code? (and likewise the cpu_clear that follows)
No. I don't see how.
> Also, in the case where p2m is NULL, when the p2m is allocated later you
> need to set a bit in p2m->p2m_dirty_cpumask there too.
The idea is that the cpu bitmap is per p2m and has the bits for all
physical cpus set whose vcpus are in guest mode.
Say, a l1 guest has four vcpus pinned on the physical cpus 0, 1, 2 and 3.
Three of them share the same p2m and the vcpus 0 and 2 are in guest mode.
When the nested p2m is flushed then only the TLBs of the pcpus 0 and 2
are flushed. The pcpu 1 flushes its TLB on VMRUN emulation.
An IPI is saved that way.
When the l1 guest runs multiple l2 smp guests then the TLB shootdown
the savings on IPI's increase.
> > }
> >
> > void
> > nestedhvm_vcpu_exit_guestmode(struct vcpu *v)
> > {
> > + struct p2m_domain *p2m;
> > vcpu_nestedhvm(v).nh_guestmode = 0;
> > -}
> > +
> > + p2m = vcpu_nestedhvm(v).nh_p2m;
> > + if (p2m == NULL)
> > + /* p2m has either been invalidated or not yet assigned. */
> > + return;
> > +
> > + cpu_clear(v->processor, p2m->p2m_dirty_cpumask);
> > +}
> >
> >
> >
> >
> > diff -r 50b3e6c73d7c -r 24daea64bdff xen/arch/x86/mm/hap/hap.c
> > --- a/xen/arch/x86/mm/hap/hap.c
> > +++ b/xen/arch/x86/mm/hap/hap.c
> > @@ -40,6 +40,7 @@
> > #include <asm/p2m.h>
> > #include <asm/domain.h>
> > #include <xen/numa.h>
> > +#include <asm/hvm/nestedhvm.h>
> >
> > #include "private.h"
> >
> > @@ -340,6 +341,30 @@ static void hap_free_p2m_page(struct p2m
> > hap_unlock(d);
> > }
> >
> > +#define nestedp2m_alloc_p2m_page hap_alloc_p2m_page
> > +
> > +/* We must use hap_free() or flushing the nested p2m tables fails
> > + * with "freeing ptp fails due to insufficient pages.
>
> That's quite sensible -- other code that frees p2m pages directly to Xen
> is basically wrong. It's a relic of the shadow allocator, where freeing
> individual p2m pages to the shadow pool would have been a bit tricky and
> I knew at the time that p2m pages were only ever freed on destruction.
>
> I really ought to update the shadow p2m-free path now that the shadow
> pool is simpler. It just needs a little care around the order things
> happen in teardown.
I'm looking forward to see your patch.
>
> > + * XXX This triggers a bug in p2m that causes a crash in
> > + * xen/common/page_alloc.c:1201 on L1 guest shutdown/destroy.
> > + */
> > +static void
> > +nestedp2m_free_p2m_page(struct p2m_domain *p2m, struct page_info *pg)
> > +{
> > + struct domain *d = p2m->domain;
> > + hap_lock(d);
> > + ASSERT(page_get_owner(pg) == d);
> > + /* Should have just the one ref we gave it in alloc_p2m_page() */
> > + BUG_ON((pg->count_info & PGC_count_mask) != 1);
> > + pg->count_info = 0;
> > + page_set_owner(pg, NULL);
> > + hap_free(d, page_to_mfn(pg));
> > + d->arch.paging.hap.total_pages++;
> > + d->arch.paging.hap.p2m_pages--;
> > + ASSERT(d->arch.paging.hap.p2m_pages >= 0);
> > + hap_unlock(d);
> > +}
> > +
> > /* Return the size of the pool, rounded up to the nearest MB */
> > static unsigned int
> > hap_get_allocation(struct domain *d)
> >
> >
> > +static int
> > +nestedp2m_next_level(struct p2m_domain *p2m, struct page_info
> > **table_pg, + void **table, unsigned long
> > *gfn_remainder, + unsigned long gfn, uint32_t shift,
> > uint32_t max, + unsigned long type)
> > +{
> > + l1_pgentry_t *l1_entry;
> > + l1_pgentry_t *p2m_entry;
> > + l1_pgentry_t new_entry;
> > + void *next;
> > + int i;
> > +
> > + ASSERT(p2m);
> > + ASSERT(p2m->alloc_page);
> > +
> > + if ( !(p2m_entry = p2m_find_entry(*table, gfn_remainder, gfn, shift,
> > max)) ) + return 0;
> > +
> > + if ( !(l1e_get_flags(*p2m_entry) & _PAGE_PRESENT) )
> > + {
> > + struct page_info *pg;
> > +
> > + pg = p2m_alloc_ptp(p2m, type);
> > + if ( pg == NULL )
> > + return 0;
> > +
> > + new_entry = l1e_from_pfn(mfn_x(page_to_mfn(pg)),
> > + __PAGE_HYPERVISOR | _PAGE_USER);
> > +
> > + switch ( type ) {
> > + case PGT_l3_page_table:
> > + nested_write_p2m_entry(p2m, p2m_entry, new_entry);
> > + break;
> > + case PGT_l2_page_table:
> > +#if CONFIG_PAGING_LEVELS == 3
> > + /* for PAE mode, PDPE only has PCD/PWT/P bits available */
> > + new_entry = l1e_from_pfn(mfn_x(page_to_mfn(pg)),
> > _PAGE_PRESENT); +#endif
> > + nested_write_p2m_entry(p2m, p2m_entry, new_entry);
> > + break;
> > + case PGT_l1_page_table:
> > + nested_write_p2m_entry(p2m, p2m_entry, new_entry);
> > + break;
> > + default:
> > + BUG();
> > + break;
> > + }
> > + }
> > +
> > + ASSERT(l1e_get_flags(*p2m_entry) & (_PAGE_PRESENT|_PAGE_PSE));
> > +
> > + /* split single large page into 4KB page in P2M table */
> > + if ( type == PGT_l1_page_table && (l1e_get_flags(*p2m_entry) &
> > _PAGE_PSE) ) + {
> > + unsigned long flags, pfn;
> > + struct page_info *pg;
> > +
> > + pg = p2m_alloc_ptp(p2m, PGT_l1_page_table);
> > + if ( pg == NULL )
> > + return 0;
> > +
> > + /* New splintered mappings inherit the flags of the old
> > superpage, + * with a little reorganisation for the _PAGE_PSE_PAT
> > bit. */ + flags = l1e_get_flags(*p2m_entry);
> > + pfn = l1e_get_pfn(*p2m_entry);
> > + if ( pfn & 1 ) /* ==> _PAGE_PSE_PAT was set */
> > + pfn -= 1; /* Clear it; _PAGE_PSE becomes
> > _PAGE_PAT */ + else
> > + flags &= ~_PAGE_PSE; /* Clear _PAGE_PSE (== _PAGE_PAT) */
> > +
> > + l1_entry = __map_domain_page(pg);
> > + for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
> > + {
> > + new_entry = l1e_from_pfn(pfn + i, flags);
> > + nested_write_p2m_entry(p2m, l1_entry+i, new_entry);
> > + }
> > + unmap_domain_page(l1_entry);
> > +
> > + new_entry = l1e_from_pfn(mfn_x(page_to_mfn(pg)),
> > + __PAGE_HYPERVISOR|_PAGE_USER);
> > + nested_write_p2m_entry(p2m, p2m_entry, new_entry);
> > + }
> > +
> > + *table_pg = l1e_get_page(*p2m_entry);
> > + next = __map_domain_page(*table_pg);
> > + unmap_domain_page(*table);
> > + *table = next;
> > +
> > + return 1;
> > +}
>
> This function looks like it duplicates a lot of logic from an old
> version of the normal p2m next-level function.
Yes, it is redundant. The point is that the *_write_p2m_entry() functions
are not nested virtualization aware. I am having troubles with understanding
the monitor p2m tables.
> Would it be easy to merge them?
Maybe, maybe not. I can answer the question when I understand the use of the
monitor table and how they work.
>
> > +int
> > +nestedp2m_set_entry(struct p2m_domain *p2m, unsigned long gfn, mfn_t
> > mfn, + unsigned int page_order, p2m_type_t p2mt);
> > +
> > +int
> > +nestedp2m_set_entry(struct p2m_domain *p2m, unsigned long gfn, mfn_t
> > mfn, + unsigned int page_order, p2m_type_t p2mt)
> > +{
> > + struct page_info *table_pg;
> > + void *table;
> > + unsigned long gfn_remainder = gfn;
> > + l1_pgentry_t *p2m_entry;
> > + l1_pgentry_t entry_content;
> > + l2_pgentry_t l2e_content;
> > + int rv = 0;
> > +
> > + ASSERT(p2m);
> > + ASSERT(p2m->alloc_page);
> > +
> > + /* address of nested paging table */
> > + table_pg = pagetable_get_page(p2m_get_pagetable(p2m));
> > + table = __map_domain_page(table_pg);
> > +
> > +#if CONFIG_PAGING_LEVELS >= 4
> > + if ( !nestedp2m_next_level(p2m, &table_pg, &table,
> > + &gfn_remainder, gfn,
> > + L4_PAGETABLE_SHIFT - PAGE_SHIFT,
> > + L4_PAGETABLE_ENTRIES, PGT_l3_page_table)
> > ) + goto out;
> > +#endif
> > +
> > + if ( !nestedp2m_next_level(p2m, &table_pg, &table, &gfn_remainder,
> > + gfn, L3_PAGETABLE_SHIFT - PAGE_SHIFT,
> > + ((CONFIG_PAGING_LEVELS == 3)
> > + ? (paging_mode_hap(p2m->domain) ? 4 : 8)
> > + : L3_PAGETABLE_ENTRIES),
> > + PGT_l2_page_table) )
> > + goto out;
> > +
> > + if ( page_order == 0 )
> > + {
> > + if ( !nestedp2m_next_level(p2m, &table_pg, &table,
> > + &gfn_remainder, gfn,
> > + L2_PAGETABLE_SHIFT - PAGE_SHIFT,
> > + L2_PAGETABLE_ENTRIES,
> > PGT_l1_page_table) ) + goto out;
> > +
> > + p2m_entry = p2m_find_entry(table, &gfn_remainder, gfn,
> > + 0, L1_PAGETABLE_ENTRIES);
> > + ASSERT(p2m_entry);
> > +
> > + if ( mfn_valid(mfn) ) {
> > + entry_content = l1e_from_pfn(mfn_x(mfn),
> > + p2m_type_to_flags(p2mt));
> > + } else {
> > + entry_content = l1e_empty();
> > + }
> > +
> > + /* level 1 entry */
> > + nested_write_p2m_entry(p2m, p2m_entry, entry_content);
> > + }
> > + else
> > + {
> > + p2m_entry = p2m_find_entry(table, &gfn_remainder, gfn,
> > + L2_PAGETABLE_SHIFT - PAGE_SHIFT,
> > + L2_PAGETABLE_ENTRIES);
> > + ASSERT(p2m_entry);
> > +
> > + /* FIXME: Deal with 4k replaced by 2MB pages */
> > + if ( (l1e_get_flags(*p2m_entry) & _PAGE_PRESENT) &&
> > + !(l1e_get_flags(*p2m_entry) & _PAGE_PSE) )
> > + {
> > + domain_crash(p2m->domain);
> > + goto out;
> > + }
> > +
> > + if ( mfn_valid(mfn) )
> > + l2e_content = l2e_from_pfn(mfn_x(mfn),
> > + p2m_type_to_flags(p2mt) | _PAGE_PSE);
> > + else {
> > + l2e_content = l2e_empty();
> > + }
> > +
> > + entry_content.l1 = l2e_content.l2;
> > + nested_write_p2m_entry(p2m, p2m_entry, entry_content);
> > + }
> > +
> > + /* Track the highest gfn for which we have ever had a valid mapping
> > */ + if ( mfn_valid(mfn)
> > + && (gfn + (1UL << page_order) - 1 > p2m->max_mapped_pfn) )
> > + p2m->max_mapped_pfn = gfn + (1UL << page_order) - 1;
> > +
> > + /* Success */
> > + rv = 1;
> > +
> > +out:
> > + unmap_domain_page(table);
> > + return rv;
> > +}
>
> Same for this: looks like it duplicates existing code.
Correct. nestedp2m_next_level() exists as long as this one
exist. And this one exists until *_write_p2m_entry() is made aware
of nested virtualization.
>
> > +int
> > +nestedhvm_hap_nested_page_fault(struct vcpu *v, paddr_t L2_gpa)
> > +{
> > + int rv;
> > + paddr_t L1_gpa, L0_gpa;
> > + struct domain *d = v->domain;
> > + struct p2m_domain *p2m, *nested_p2m;
> > +
> > + p2m = p2m_get_hostp2m(d); /* L0 p2m */
> > + nested_p2m = p2m_get_nestedp2m(v, vcpu_nestedhvm(v).nh_vm_hostcr3);
> > +
> > + /* walk the L1 P2M table, note we have to pass p2m
> > + * and not nested_p2m here or we fail the walk forever,
> > + * otherwise. */
>
> Can you explain that more fully? It looks like you're walking the L0
> table to translate an L2 gfn into an L1 gfn, which surely can't be right.
The l1 guest hostcr3 is in l1 guest physical address space. To walk the
l1 guest's page table I need to translate it into host physical address space
by walking the l0 p2m table.
> > + rv = nestedhap_walk_L1_p2m(v, p2m, L2_gpa, &L1_gpa);
This translates the l2 guest physical address into
l1 guest physical address and check if the l1 guest page table
walk was successful:
> > +
> > + /* let caller to handle these two cases */
> > + switch (rv) {
> > + case NESTEDHVM_PAGEFAULT_INJECT:
> > + return rv;
> > + case NESTEDHVM_PAGEFAULT_ERROR:
> > + return rv;
> > + case NESTEDHVM_PAGEFAULT_DONE:
> > + break;
> > + default:
> > + BUG();
> > + break;
> > + }
> > +
Here we know the l1 guest page table walk was successful so translate
the l1 guest physical address into host physical address.
> > + /* ==> we have to walk L0 P2M */
> > + rv = nestedhap_walk_L0_p2m(p2m, L1_gpa, &L0_gpa);
> > +
> > + /* let upper level caller to handle these two cases */
> > + switch (rv) {
> > + case NESTEDHVM_PAGEFAULT_INJECT:
> > + return rv;
> > + case NESTEDHVM_PAGEFAULT_ERROR:
> > + return rv;
> > + case NESTEDHVM_PAGEFAULT_DONE:
> > + break;
> > + default:
> > + BUG();
> > + break;
> > + }
Here we know the walk was successfull so we can fix the nestedp2m.
> > + /* fix p2m_get_pagetable(nested_p2m) */
> > + nestedhap_fix_p2m(nested_p2m, L2_gpa, L0_gpa);
> > +
> > + return NESTEDHVM_PAGEFAULT_DONE;
> > +}
> > +
> > +/********************************************/
> > +/* NESTED VIRT INITIALIZATION FUNCS */
> > +/********************************************/
> > +
> > +/*
> > + * Local variables:
> > + * mode: C
> > + * c-set-style: "BSD"
> > + * c-basic-offset: 4
> > + * tab-width: 4
> > + * indent-tabs-mode: nil
> > + * End:
> > + */
> > diff -r 50b3e6c73d7c -r 24daea64bdff xen/arch/x86/mm/hap/private.h
> > --- a/xen/arch/x86/mm/hap/private.h
> > +++ b/xen/arch/x86/mm/hap/private.h
> > @@ -30,4 +30,14 @@ unsigned long hap_gva_to_gfn_3_levels(st
> > unsigned long hap_gva_to_gfn_4_levels(struct vcpu *v, unsigned long gva,
> > uint32_t *pfec);
> >
> > +unsigned long hap_p2m_ga_to_gfn_2_levels(struct vcpu *v,
> > + struct p2m_domain *p2m, unsigned long cr3,
> > + paddr_t ga, uint32_t *pfec);
> > +unsigned long hap_p2m_ga_to_gfn_3_levels(struct vcpu *v,
> > + struct p2m_domain *p2m, unsigned long cr3,
> > + paddr_t ga, uint32_t *pfec);
> > +unsigned long hap_p2m_ga_to_gfn_4_levels(struct vcpu *v,
> > + struct p2m_domain *p2m, unsigned long cr3,
> > + paddr_t ga, uint32_t *pfec);
> > +
> > #endif /* __HAP_PRIVATE_H__ */
> > diff -r 50b3e6c73d7c -r 24daea64bdff xen/arch/x86/mm/p2m.c
> > --- a/xen/arch/x86/mm/p2m.c
> > +++ b/xen/arch/x86/mm/p2m.c
> > @@ -34,6 +34,7 @@
> > #include <public/mem_event.h>
> > #include <asm/mem_sharing.h>
> > #include <xen/event.h>
> > +#include <asm/hvm/nestedhvm.h>
> >
> > /* Debugging and auditing of the P2M code? */
> > #define P2M_AUDIT 0
> > @@ -72,7 +73,7 @@ boolean_param("hap_1gb", opt_hap_1gb);
> > #define SUPERPAGE_PAGES (1UL << 9)
> > #define superpage_aligned(_x) (((_x)&(SUPERPAGE_PAGES-1))==0)
> >
> > -static unsigned long p2m_type_to_flags(p2m_type_t t)
> > +unsigned long p2m_type_to_flags(p2m_type_t t)
> > {
> > unsigned long flags;
> > #ifdef __x86_64__
> > @@ -116,9 +117,9 @@ static void audit_p2m(struct p2m_domain
> > // Find the next level's P2M entry, checking for out-of-range gfn's...
> > // Returns NULL on error.
> > //
> > -static l1_pgentry_t *
> > +l1_pgentry_t *
> > p2m_find_entry(void *table, unsigned long *gfn_remainder,
> > - unsigned long gfn, u32 shift, u32 max)
> > + unsigned long gfn, uint32_t shift, uint32_t max)
> > {
> > u32 index;
> >
> > @@ -1719,10 +1720,12 @@ static void p2m_initialise(struct domain
> > INIT_PAGE_LIST_HEAD(&p2m->pod.single);
> >
> > p2m->domain = d;
> > + p2m->cr3 = 0;
> > p2m->set_entry = p2m_set_entry;
> > p2m->get_entry = p2m_gfn_to_mfn;
> > p2m->get_entry_current = p2m_gfn_to_mfn_current;
> > p2m->change_entry_type_global = p2m_change_type_global;
> > + cpus_clear(p2m->p2m_dirty_cpumask);
> >
> > if ( hap_enabled(d) && (boot_cpu_data.x86_vendor ==
> > X86_VENDOR_INTEL) ) ept_p2m_init(d);
> > @@ -1730,6 +1733,28 @@ static void p2m_initialise(struct domain
> > return;
> > }
> >
> > +extern int
> > +nestedp2m_set_entry(struct p2m_domain *p2m, unsigned long gfn, mfn_t
> > mfn, + unsigned int page_order, p2m_type_t p2mt);
>
> Please define this in a header file.
This will go away along with the code duplication
we talked above. Is it ok to keep it here until then?
> > +static int
> > +p2m_init_nestedp2m(struct domain *d)
> > +{
> > + uint8_t i;
> > + struct p2m_domain *p2m;
> > +
> > + spin_lock_init(&d->arch.nested_p2m_lock);
> > + for (i = 0; i < MAX_NESTEDP2M; i++) {
> > + d->arch.nested_p2m[i] = p2m = xmalloc(struct p2m_domain);
> > + if (p2m == NULL)
> > + return -ENOMEM;
> > + p2m_initialise(d, p2m);
> > + p2m->set_entry = nestedp2m_set_entry;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > int p2m_init(struct domain *d)
> > {
> > struct p2m_domain *p2m;
> > @@ -1739,7 +1764,11 @@ int p2m_init(struct domain *d)
> > return -ENOMEM;
> > p2m_initialise(d, p2m);
> >
> > - return 0;
> > + /* Must initialise nestedp2m unconditionally
> > + * since nestedhvm_enabled(d) returns false here.
> > + * (p2m_init runs too early for HVM_PARAM_* options)
> > + */
> > + return p2m_init_nestedp2m(d);
> > }
> >
> > void p2m_change_entry_type_global(struct p2m_domain *p2m,
> > @@ -1836,6 +1865,9 @@ int p2m_alloc_table(struct p2m_domain *p
> > p2m_invalid) )
> > goto error;
> >
> > + if (p2m_is_nestedp2m(p2m))
> > + goto nesteddone;
> > +
> > /* Copy all existing mappings from the page list and m2p */
> > spin_lock(&p2m->domain->page_alloc_lock);
> > page_list_for_each(page, &p2m->domain->page_list)
> > @@ -1857,6 +1889,7 @@ int p2m_alloc_table(struct p2m_domain *p
> > }
> > spin_unlock(&p2m->domain->page_alloc_lock);
> >
> > + nesteddone:
> > P2M_PRINTK("p2m table initialised (%u pages)\n", page_count);
> > p2m_unlock(p2m);
> > return 0;
> > @@ -1881,6 +1914,9 @@ void p2m_teardown(struct p2m_domain *p2m
> > mfn_t mfn;
> > #endif
> >
> > + if (p2m == NULL)
> > + return;
> > +
> > p2m_lock(p2m);
> >
> > #ifdef __x86_64__
> > @@ -1899,11 +1935,26 @@ void p2m_teardown(struct p2m_domain *p2m
> > p2m_unlock(p2m);
> > }
> >
> > +static void p2m_teardown_nestedp2m(struct domain *d)
> > +{
> > + uint8_t i;
> > +
> > + for (i = 0; i < MAX_NESTEDP2M; i++) {
> > + xfree(d->arch.nested_p2m[i]);
> > + d->arch.nested_p2m[i] = NULL;
> > + }
> > +}
> > +
> > void p2m_final_teardown(struct domain *d)
> > {
> > /* Iterate over all p2m tables per domain */
> > xfree(d->arch.p2m);
> > d->arch.p2m = NULL;
> > +
> > + /* We must teardown unconditionally because
> > + * we initialise them unconditionally.
> > + */
> > + p2m_teardown_nestedp2m(d);
> > }
> >
> > #if P2M_AUDIT
> > @@ -2823,6 +2874,173 @@ void p2m_mem_paging_resume(struct p2m_do
> > }
> > #endif /* __x86_64__ */
> >
> > +static struct p2m_domain *
> > +p2m_getlru_nestedp2m(struct domain *d, struct p2m_domain *p2m)
> > +{
> > + int i, lru_index = -1;
> > + struct p2m_domain *lrup2m, *tmp;
> > +
> > + if (p2m == NULL) {
> > + lru_index = MAX_NESTEDP2M - 1;
> > + lrup2m = d->arch.nested_p2m[lru_index];
> > + } else {
> > + lrup2m = p2m;
> > + for (i = 0; i < MAX_NESTEDP2M; i++) {
> > + if (d->arch.nested_p2m[i] == p2m) {
> > + lru_index = i;
> > + break;
> > + }
> > + }
> > + }
> > +
> > + ASSERT(lru_index >= 0);
> > + if (lru_index == 0) {
> > + return lrup2m;
> > + }
> > +
> > + /* move the other's down the array "list" */
> > + for (i = lru_index - 1; i >= 0; i--) {
> > + tmp = d->arch.nested_p2m[i];
> > + d->arch.nested_p2m[i+1] = tmp;
> > + }
> > +
> > + /* make the entry the first one */
> > + d->arch.nested_p2m[0] = lrup2m;
> > +
> > + return lrup2m;
> > +}
> > +
> > +static int
> > +p2m_flush_locked(struct p2m_domain *p2m)
> > +{
> > + struct page_info * (*alloc)(struct p2m_domain *);
> > + void (*free)(struct p2m_domain *, struct page_info *);
> > +
> > + alloc = p2m->alloc_page;
> > + free = p2m->free_page;
> > +
> > + if (p2m->cr3 == 0)
> > + /* Microoptimisation: p2m is already empty.
> > + * => about 0.3% speedup of overall system performance.
> > + */
> > + return 0;
>
> What happens if a malicious guest uses 0 as its actual CR3 value?
When l1 guest uses hap and l2 guest uses shadow paging, this code path
never runs.
When l1 guest uses hap and l2 guest uses hap, this is can only be the
guest's hostcr3.
So your question is what happens if a malicious guest uses 0 to point to
its nested page table ?
I think, this guest crashes sooner or later anyway.
> > +
> > + p2m_teardown(p2m);
> > + p2m_initialise(p2m->domain, p2m);
> > + p2m->set_entry = nestedp2m_set_entry;
> > + BUG_ON(p2m_alloc_table(p2m, alloc, free) != 0);
> > +
> > + ASSERT(p2m);
> > + ASSERT(p2m->alloc_page);
> > + return 0;
> > +}
> > +
> > +void
> > +p2m_flush(struct vcpu *v, struct p2m_domain *p2m)
> > +{
> > + struct domain *d = p2m->domain;
> > +
> > + nestedhvm_vm_flushtlb(p2m);
> > + ASSERT(v->domain == d);
> > + vcpu_nestedhvm(v).nh_p2m = NULL;
> > + spin_lock(&d->arch.nested_p2m_lock);
> > + BUG_ON(p2m_flush_locked(p2m) != 0);
> > + spin_unlock(&d->arch.nested_p2m_lock);
> > + hvm_asid_flush_vcpu(v);
> > +}
> > +
> > +void
> > +p2m_flush_nestedp2m(struct domain *d)
> > +{
> > + int i;
> > +
> > + spin_lock(&d->arch.nested_p2m_lock);
> > + for (i = 0; i < MAX_NESTEDP2M; i++)
> > + BUG_ON(p2m_flush_locked(d->arch.nested_p2m[i]) != 0);
> > + spin_unlock(&d->arch.nested_p2m_lock);
> > + flush_tlb_mask(&d->domain_dirty_cpumask);
> > +}
> > +
> > +struct p2m_domain *
> > +p2m_get_nestedp2m(struct vcpu *v, uint64_t cr3)
> > +{
> > + struct nestedhvm *hvm = &vcpu_nestedhvm(v);
> > + struct domain *d;
> > + struct p2m_domain *p2m;
> > + int i, rv;
> > +
> > + if (cr3 == 0)
> > + cr3 = v->arch.hvm_vcpu.guest_cr[3];
> > +
> > + if (hvm->nh_flushp2m && hvm->nh_p2m) {
> > + nestedhvm_vm_flushtlb(hvm->nh_p2m);
> > + hvm->nh_p2m = NULL;
> > + }
> > +
> > + d = v->domain;
> > + spin_lock(&d->arch.nested_p2m_lock);
> > + for (i = 0; i < MAX_NESTEDP2M; i++) {
> > + p2m = d->arch.nested_p2m[i];
> > + if (p2m->cr3 == cr3 && p2m == hvm->nh_p2m) {
> > + p2m_getlru_nestedp2m(d, p2m);
> > + if (hvm->nh_flushp2m) {
> > + BUG_ON(p2m_flush_locked(p2m) != 0);
> > + hvm->nh_flushp2m = 0;
> > + hvm_asid_flush_vcpu(v);
> > + }
> > + p2m->cr3 = cr3;
> > + spin_unlock(&d->arch.nested_p2m_lock);
> > + return p2m;
> > + }
> > + if (p2m->cr3 == 0) { /* found unused p2m table */
> > + hvm->nh_flushp2m = 0;
> > + p2m_getlru_nestedp2m(d, p2m);
> > + hvm->nh_p2m = p2m;
> > + p2m->cr3 = cr3;
> > + spin_unlock(&d->arch.nested_p2m_lock);
> > + hvm_asid_flush_vcpu(v);
> > + return p2m;
> > + }
> > + }
> > +
> > + /* All p2m's are or were in use. We know the least recent used one.
> > + * Destroy and re-initialize it.
> > + */
> > + for (i = 0; i < MAX_NESTEDP2M; i++) {
> > + p2m = p2m_getlru_nestedp2m(d, NULL);
> > + rv = p2m_flush_locked(p2m);
>
> Is this enough? If this p2m might be in host_vmcb->h_cr3 somewhere on
> another vcpu, then you need to make sure that vcpu gets reset not to use
> it any more.
There are three possibilities:
An other vcpu is in VMRUN emulation before a nestedp2m is assigned.
In this case, it will get a new nestedp2m as it won't find its 'old'
nestedp2m anymore.
An other vcpu is in VMRUN emulation after a nestedp2m is assigned.
It will VMEXIT with a nested page fault.
An other vcpu already running l2 guest.
It will VMEXIT with a nested page fault immediately.
Christoph
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